building science text book series

Part 1: Appropriate Roofing & Energy Considerations for Warm-Humid Climates: _____________________________________________________________________________________________

BUILDING SCIENCE TEXT BOOK SERIES: BOOK 3: PART 1:

TOPICAL THEMES: APPROPRIATE ROOFING & ENERGY CONSIDERATIONS FOR WARM-HUMID CLIMATES:

Yusuf Hazara Ebrahim. ISBN: 9966-784-19-5 Code: E3100 Retail Price: Kshs, 1,990/- (US $35)

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_______________________________________________________________________________________________________________ Page: 1 of 145 Building Science Text Book Series: Book 3: Topical Themes:

Yusuf H. Ebrahim



TOPICAL THEMES: APPROPRIATE ROOFING & ENERGY CONSIDERATIONS FOR WARM-HUMID CLIMATES:

Yusuf Hazara Ebrahim. AUTHOR: DEDICATION: TO:

AND:

Ebenergy Enterprises

Code: E3100 ISBN: 9966-784-19-5

My Family:

Wife: Sons: Daughter:

Hawa Abdulrasul Achu Ebrahim, Ebrahim & Imran Y. Ebrahim, Hannan Y. Ebrahim.

‘Thank you for your patience and perseverance during this period of turbulence and uncertainty. Also for your faith and belief in the ordained’ My Extended Family: To: My Late Mum: and Late Dad: Mrs. Lillian Lela Ebrahim Orloff. Mr. Ebrahim Atma Singh Hazara Singh. (01/05/1936 to 01/09/2000) (02/01/1934 to 04/06/2004)

Late: Elder Sister Shamim E.A. Abdulkayum, Her Children: Sabrina A.A. Abdulrahim, Abdulkadir Abdulkayum & Siraj Abdulkayum, Surviving Sister: Shama E. Matharu, Her Children: Simran Matharu, Sharman Matharu, Sonan Matharu & Sanny Matharu, Brother: Ayub H. Ebrahim & wife Dolat K.A. Ebrahim, Their Children: Deleila A. Ebrahim, Mariam A. Ebrahim & Arfan A. Ebrahim, Brother: Twalib H. Ebrahim & wife Sultana T. Ebrahim, Their Children: Saadah T. Ebrahim, Mohammed T. Ebrahim & Salmaan T. Ebrahim, Youngest Brother: Nazir H. Ebrahim. ‘Forgive me for all my trespasses, excesses and for not achieving my potential. For I’m only a mortal and Almighty God knows best for all of us’.


Yusuf H. Ebrahim

Part 1: Appropriate Roofing & Energy Considerations for Warm-Humid Climates: _____________________________________________________________________________________________ Yusuf H. Ebrahim can be contacted: Address: Ebenergy Enterprises, Unit 1, Ebrahim House, 4th Avenue Parklands, P.O. Box 34838, 00100 GPO Nairobi, Kenya. Website: www.ebenergy.net Email: [email protected] or [email protected] or [email protected] Email: [email protected] Tel: +254 020 3751239 Mobile: +254 722513617.

©Yusuf Hazara Ebrahim. All rights reserved. No part of this book may be reproduced, stored in a retrieval system, or transcribed, in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without the prior written permission of the copyright holder.

Ebenergy Enterprises: Code: E3100 ISBN: 9966-784-19-5 First Published: 2008.

Published and Printed by Ebenergy Enterprises.


Yusuf H. Ebrahim


BUILDING SCIENCE TEXT BOOK UON SERIES:

BOOK 3:

TOPICAL THEMES:

PART 1:

APPROPRIATE ROOING AND ENERGY CONSIDERATIONS FOR WARM-HUMID CLIMATES: Author:

Yusuf H. Ebrahim, B’Arch. Hons (Nbi), M’Phil. (CANTAB), MAAK(A).

Ebenergy Enterprises Nairobi, Kenya. _______________________________________________________________________________________________________________ Page: 4 of 145 Building Science Text Book Series: Book 3: Topical Themes:

Yusuf H. Ebrahim



TOPICAL THEMES: APPROPRIATE ROOING AND ENERGY CONSIDERATIONS FOR WARMHUMID CLIMATES: Initially submitted as part of the Master of Philosophy Examinations in Architecture, Option B: Environmental Design Dissertation. EBRAHIM, Yusuf University of Cambridge, Faculty or Architecture and History of Art, 1987/88. _______________________________________________________________________________ DEDICATION AT M’PHIL LEVEL: To my family: My Late: Mum and Dad, My Late Sister: Shamim, My Sister: Shama, My Brothers: Ayub, Twalib and Nazir. _______________________________________________________________________________ ACKNOWLEDGEMENT AT M’PHIL LEVEL: “In the name of God, Most Gracious, Most Merciful. Read: In the name of thy Lord who created, Who created man from something which clings. Who taught by the pen. Who taught man what he did not know. The Quran, Sura Al’Alaq, 96:1-5. I would like to thank the following for their help and encouragement: Dr. N.V. Baker (My supervisor and teacher) for his kindness and guidance during the computer simulation work and the writing of this dissertation. Dr. D. Hawkes for his advice and comments on the draft. Mr. R. W’O Okot-uma (Project Officer, Commonwealth Science Council, London) and Dr. R. Spence (Martin Centre, University of Cambridge) for the numerous consultative talks on specific technical subjects and the use of their personal books. Dr. E. Meffert (Chairman, University of Nairobi, Kenya) for his help on the collection of climatic data. Mr. S. Claydon (Architect, residing in Woodbridge, Suffolk) on the use of his personal architectural books. Mr. G.T. Wilson (Secretary, Commonwealth Association of Architects, London) on arranging a visit to S. Denyer’s talk on appropriate materials. Mr. W. Okeyo (Architect, Nairobi), Mr. J. Chaudhry (Assistant Architect, Nairobi), Miss. H. Achu (Secretary, Mombasa) and Mrs. S. Abdul Kayum (Secretary, Nairobi) for their help with the questionnaires (Appendix). Mr. F. Ip (Post Graduate, University of Cambridge) for plotting some graphs of the simulation results. And to my family and all the friends that I have made in Cambridge, for all their advise and words of inspiration. May Almighty Allah be pleased with them. _______________________________________________________________________________________________________________ Page: 5 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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TOPICAL THEMES: APPROPRIATE ROOING AND ENERGY CONSIDERATIONS FOR WARMHUMID CLIMATES:

CONTENT:

Page:

_____________________________________________________________________________________________

SCOPE AND LIMITATIONS: METHODOLOGY: INTRODUCTION: CHAPTER 1: THE ENERGY SCENE IN TROPICAL COUNTRIES: 1.0 National energy demand: 1.1 Tropical conditions: 1.2 Building trends: 1.3 Environmental roof design for the tropics: 1.4 Concluding remarks:

CHAPTER 2: CREATION OF A MODEL: 2.1 Roof in the tropics: 2.2 Criteria for evaluation: 2.2.1 Conductivity and conductance: 2.2.2 Solar heat gain factor (SHF): 2.2.3 Time-lag: 2.2.4 Ceiling temperatures: 2.3 Simulation work: 2.4 Test cell: 2.5 Concluding remarks:

CHAPTER 3: CAPITAL ENERGY: 3.1 Energy data in developing countries: 3.2 Materials classification based on energy use: 3.21 High energy materials: 3.22 Medium energy materials: 3.23 Low energy materials: 3.3 Energy to build different roof elements: 3.31 Structure: _______________________________________________________________________________________________________________ Page: 6 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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3.32 Roofing: 3.33 Ceiling: 3.34 Finishes: 3.35 Extras: 3.4 Total capital energy for different roofs: 3.5 Concluding remarks:

CHAPTER 4: OPERATING ENERGY: 4.1 Effective surface area and solar exposure: 4.2 Roofing materials: 4.3 Ceiling temperature and comfort requirements: 4.31 Integrated design: 4.32 Reflective exterior finish: 4.33 Insulated lining: 4.34 Thickness of various materials: 4.35 Ventilated cavity: 4.4 Solar heat gain factor (SHF): 4.5 Time-lag: 4.6 Concluding remarks:

CHAPTER 5: ENERGY BALANCE: 5.1 Cost and performance of different roofs: 5.2 Energy rating and comfort levels: 5.3 Energy policy and economic direction: 5.4 Concluding remarks:

CONCLUSIONS: REFERENCES: APPENDIX:


Yusuf H. Ebrahim


SCOPE AND LIMITATIONS: _____________________________________________________________________ The topic of “Appropriate roofing and energy considerations for warm-humid climates” is very extensive dealing with three, though interconnected subjects, i.e. materials, a climate and the energy implication. Each of which demands a study of its own, but which would be too great a task for an M’Phil dissertation. In order to satisfy the latter, the author has limited his study, by restricting his investigations of roofs to a small number of samples, most of which he has observed in his own country (Kenya). This presentation is not supposed to be exhaustive, rather, it is hoped that it may act as a pilot study for future work that the author hopes to conduct at a PhD or M.Sc level. Each of the above three subjects is critical in deciding the rate and direction of development in different countries. In the last twenty years, a lot of controversy has been started due to the misunderstanding between the various planning authorities. The word “development” carries with it numerous interpretations and the author will restrict himself to the environmental and physiological considerations. The purpose of this study is to evaluate the current situation within developing countries, notably those with a warm-humid climate, with the intention of extracting suitable recommendations related to energy, and the eventual production of materials that perform to sound environmental standards. This study has been divided into five main chapters: Chapter 1: Outlines the present energy, climatic and built form conditions in developing countries with particular reference to Kenya. This restriction has been imposed, so as not to distract the reader from the main theme. Chapter 2: Deals with the different issues associated with developing performance quantitative analysis techniques. A standard test cell is defined and the reader is introduced to the simulation model to be used and the assumptions pertaining to such work. Chapter 3: Analyses the energy used in manufacturing, transporting and constructing different materials and roof elements. The aim is to use this information as a basis of evaluating the effectiveness of different roofs in chapter 5.


Yusuf H. Ebrahim


Chapter 4: This is the actual simulation work on two main roof forms (a third roof is introduced for the purpose of comparison). The roof sample was limited due to the scope of this dissertation. But also, the author’s intention was to concentrate his investigation on specific physical properties of materials and to study the effect of modifications to these, rather than a more general description. Energy issues related to air-conditioning and heat flow through the fabric are also tackled. Chapter 5: Acts as a summary of the previous chapters and discusses recommendations relevant to an effective energy policy. The chapter ends with some general conclusions about the future use of materials and the implications of these.


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METHODOLOGY: _______________________________________________________________________________ The lack of a centralized information network on energy and building materials for the area under investigation necessitated the author to make use of modified information from the developed countries. This was especially critical when considering the energy used in manufacturing and constructing building elements. We have had to assume that the energy that is used for manufacturing as similar in both developing and developed countries (e.g. the energy that goes into producing a brick is probably the same due to the efficiency of the plant). Thus the author didn’t find it to be a handicap to use the same figures in this study. Apart from the analysis carried out by other workers, a simulation model is used to predict the performance of different roofs. Again, information on indigenous materials is lacking and some intelligent assumptions had to be made. Climatic data was obtained from the Meteorological Department (Kenya). These are given as daily solar radiation figures were given in the form of sunlight hours per day rather than the actual energy incident on an area. Thus, the computed solar radiation for a clear sky was used instead. A questionnaire was also compiled and sent to a few individuals (Appendix 5.1 and 5.2). The information was required to fill in the gaps within the available knowledge. But the limitation of time and sample finally made it difficult to use all of this information. Communication, both verbal and written, with scientific bodies and architectural firms in Kenya was also undertaken.


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INTRODUCTION: _____________________________________________________________________ Whenever the word “energy” is mentioned, people have different images of it. To a physicist, it is related to that which makes work possible. It can neither be seen not touched, thus making it difficult for many to visualize its importance. A businessman will try to reduce the consumption of energy, as it forms a major expense that has an effect of increasing the product cost and thereby reducing his profit. It is for this reason that the capitalist economy would be concerned and thereby invest in appropriate research. At the national level energy saved in one part of the economy can be used in another. Assuming a world with limited resources, the conservation of energy cannot be over emphasized. Yet in the developing countries, energy issues are only now being considered. It is ironic that the countries with the highest energy imports are the same ones not giving it top priority. This situation has developed for a number of reasons. As stated earlier energy is a new word, especially to most developing countries. Most of the African Languages didn’t have an equivalent word for energy. During a recent conference in Nairobi (Kenya) on renewable sources of energy, a new word “Naciti”, suddenly appeared in Kiswahili (Which is the national language in Kenya). Most developing countries are going through the second phase of development. The first phase of development was experienced just after independence of these countries and was characterized by people “Blindly” using whatever they observed in the developed countries. The second phase is a “Questioning Period”. Forced by rising costs of all imported items and a deep concern to retain the country’s identity, the developing countries are now evaluating all the sectors of their economies, with the aim of making them more efficient. The third phase of development is related to “Innovation”. This will take time to attain though some parts of the economy have shown signs of achieving the third phase. Experimentation and research are an integral part of innovation. An evaluation of building materials and construction industries by UNIDO (1976) showed that cement and allied materials were so familiar in their applications, so basic to a great range of buildings that some developing countries may fail to explore the possibility of developing other technologies based on maximum utilization of local resources and the conservation of energy. A study of the energy used in producing different items can shed light on various ways of improving existing technologies and other problems hitherto left unexplained. It is becoming evident that it is not just important to control the importation of energy in the form of liquid and gaseous fuels, but also controlling the importation of materials which use high levels _______________________________________________________________________________________________________________ Page: 11 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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of energy in production. K. Mathu (1987) observed that reinforced concrete entailed expensive energy use and consumed precious timber as shuttering, thus, indirectly affecting the natural conservation government policy. Energy consumption figures may give a more realistic impression of the performance of an economy, rather than monetary values. The prices of fuels rose sharply after the 1970 energy crises, though the actual production had remained constant and in some cases, it had reduced. This makes it difficult to compare the production and efficiency of different energy sources. There is also the problem of different currencies and exchange rates. Price indices can also create an illusion, whereby people believe that if they had enough money, the supply of energy would not be a problem. Studies by Chapman (1975) showed that the world energy sources reserves are being depleted at such a fast rate that, if no new energy sources are discovered, the efficiency of producing these fuels will depreciate and the prices will rise. Chapman also suggests an alternative strategy of looking at the energy demand. If we consider the construction industry, energy consumption can be reduced by controlling the energy required for production, transporting and constructing buildings. This can be done by using materials that didn’t require large energy inputs and by using materials that are locally available, so as to reduce transportation costs. Labour intensive methods should also be considered. The relationship between climate and energy use is also interesting. When considering tropical countries with high temperatures and humidity, large amounts of energy goes into maintaining comfort levels through use of air-conditioning. The following pages will try to investigate ways of reducing this load without increasing the use of high energy consumption materials. Roof forms are important in tropical countries for a number of reasons. The large angle of incidence of the sun in tropical countries ensures that the roof receives the largest amount of solar radiation. A large area of the wall will be shaded by the roof and by the surrounding vegetation. The roof is also the largest element and is usually the most expensive1. If we consider the building fabric as a filter, allowing favorable climatic elements such as useful solar radiation and daylight to penetrate, while excluding harmful elements, such as rain and excessive heat or winds, it now becomes imperative that this large surface should be designed so that minimal harmful elements may penetrate the envelope2.

1

Koenigsberger and Lynn: 1965. Koenigsberger et al: 1978. _______________________________________________________________________________________________________________ Page: 12 of 145 2

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The success of a low cost housing design may also depend on an effective roof. The roof overhung will protect the walls which are usually made of intermediate materials such as adobe or mud on wattle. Parallels may be drawn to a saying in Cornwall (England), related to cob buildings. It is said that “all cob needs is a good hat and a good pair of boots”, referring to the overhanging roof and the brick layers protecting the foundation3. Traditional buildings were tried and tested over a long period of use and adaptation. In many cases the old materials may be unsuitable for modern living, though many people find a mud floor and a thatched or mud roof is far more comfortable than a concrete floor and a tin roof4. This is because most modern materials are “specific” in nature, designed to satisfy a limited range of functions. In contrast, a traditional thatched roof was made thick enough so that it acted as a thermal barrier while protecting the inhabitants from the rain and it permitted ventilation to diffuse through. The thatch roof didn’t need any finishes, ceiling or extra items. Maintenance was done by just adding more of the same material on an annual basis. A corrugated iron sheet (CIS) roof will only shelter the occupants from the rain. Other materials have to be incorporated so as to improve the roof thermal, acoustic and structural performance. A CIS roof has to be painted regularly if it is to maintain its performance5. Between the extreme cases of modern and traditional materials, there exists an array of “appropriate” or intermediate materials. Fibre concrete roof tiles (FCT) are gaining popularity in many developing countries. They have been tested for their strength, durability and production potential, but as yet, very little research has been done on the energy consumption and thermal performance. The author hopes that the following pages can make a contribution in this direction and also in addressing the overall housing problem.

3

Agarwal: 1982. Denyer: 1978. 5 Koenigsberger and Lynn: 1965. _______________________________________________________________________________________________________________ Page: 13 of 145 4


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1.0 CHAPTER 1: THE ENERGY SCENE IN TROPICAL COUNTRIES: _____________________________________________________________________ Before the oil crises of the early nineteen seventies, fuel prices were so low that relatively uneconomical fuel reserves were not exploited. Fibre wastes with low energy content, such as sawdust and coconut shells, were not used for manufacturing purposes. But the dramatic rise in oil prices in 1973/74, coupled by the large demand for this type of energy source which had constantly risen during the years, has resulted in major changes in the world economies. The developing countries were seriously affected because of their dependence on imported fuels. Before 1973, the oil import bill for Kenya averaged around 8 percent of the total imports, but after exporting the refined products, the foreign exchange component was recouped and therefore, the importation of crude oil did not pose any balance of payments problems. Since then, the prices have increased over 14 times and the export market has shrunk considerably. Oil import is now the largest single drain of foreign exchange earnings6. An economist will propose two ways of tackling the energy problem. The first would be to find new supplies and sources of energy. This is the current trend adopted by most of the countries of the world. Developed countries look for new oil fields while developing countries try to incorporate renewable sources of energy7 into a rigid economic system. At the current rate of energy consumption, numerous people have predicted a sure economic disaster for the world economies within the next century8. The second method would be to control the energy demand by analyzing the way that energy is used and finding ways of reducing the overall energy consumption. This is a method advocated by Chapman, who believes that it will ensure that the available energy reserves will last for a longer period until new sources can be discovered or conversely, better ways of exploiting the earth’s resources can be developed. This idea can be taken further, by considering each individual country and trying to control the national energy demand.

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Moi: 1984. E.g. Solar and Wind Energy. 8 Chapman: 1975. _______________________________________________________________________________________________________________ Page: 14 of 145 7


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1.1 NATIONAL ENERGY DEMAND: A glimpse at the energy balance sheet9 for a developing country will reveal the large deficit between the imports and exports of energy. Kenya is no exception as will be seen in Table 1.4. In 1980, there was 113.98 million GJ (Giga-Joules) commercial energy demand10 and 329.48 million GJ non-commercial energy demand11. Approximately 31% of the total energy demand is imported from other countries12. A large percentage of the national energy demand is lost through distribution losses and the relative inefficiencies of the fuel industries13. Approximately 4% of the total energy demand of Kenya is lost through distribution losses and 21% through electricity generation and inefficiency of the fuel industries (Table 1.4). In fact, the efficiency of electricity is very low, rated at 22% in 1963 compared to 95.5% for coal and 80.8% for oil (Table 1.1). The efficiency of electricity has been improved to 25.2% in 1975, but still ranks behind coal or oil. This is due to thermodynamic reasons relating to the conversion of thermal energy to mechanical energy and not to any shortcomings of the equipment or workers14. Hydro-electric power stations are more efficient compared to a fuel powered generator, as there is no thermal energy conversion in the former case. Most of Kenya’s electricity is got through tapping the main two rivers15. The remainder of the national energy demand is shared between the various sectors of the economy. Out of the 332 million GJ net energy, the largest share goes to the domestic sector (194 million GJ) and the manufacture and construction sector (80 million GJ) (Fig. 1.1). Ironically, these two sectors are the main suppliers of fuel and materials for constructing residential buildings and domestic appliances (Fig. 1.2). Reductions in the consumption of energy for the “house and home” will have a great impact on the net national energy demand. This is because there are a large number of households in the country, and savings16 will be multiplied greatly at the national level. During the planned period 1984-8817, approximately 1 million housing units were required in both the urban and rural areas of Kenya. If this requirement is realized with significant energy savings at the individual unit’s level, this will cause a significant reduction in the national energy demand.

9

Which shows the energy supply and how it is used. Including fossil fuels and electrical energy. 11 Including fuel wood, charcoal and biomass residue. 12 O’Keefe et al: 1984. 13 This is to do with the physical process of converting one form of energy to another (Baker: 1987). 14 Baker: 1987. 15 Tana River and Athi River. 16 However small it may be. 17 Moi: 1984. _______________________________________________________________________________________________________________ Page: 15 of 145 10


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Table 1.1: Efficiencies of the fuel industries (%). 1963 1968 1972 Coal: 95.5 96.0 95.5 Coke: 75.5 84.7 88.0 Gas: 64.7 71.9 81.1 Oil: 80.8 88.2 89.6 Electricity: 22.0 23.9 25.2 Efficiency of the fuel industry = (delivered energy to consumer x 100) / primary fuel input. Source:

Chapman: 1975.

Table 1.2: Effect of vehicle size on energy used in transport. Cargo capacity of vehicle: Average energy to move 1 tonne 1km. (Tonnes). KWh(th). 0.35 3.37 0.75 2.80 1.0 1.49 3.0 0.78 7.0 0.47 12.0 0.39 20.0 0.31 22.0 0.29 Source:

Haseltine: 1975.

Chapman identifies six main ways that the energy for “house and home” will be used (Fig. 1.2). I will only be dealing with the energy used for domestic fuel, house building and domestic durables. This is because, I want to find ways of reducing energy consumption through improved building design. Domestic fuel is used for cooking, heating, lighting and other uses. While the consumer durables may include a fan or air-conditioning unit. Apart from the user habits ad lifestyle, the performance of the building fabric and how it responds to changes in climatic conditions will have a deciding influence on the choice and use of the above items. About 12% of the Kenyan urban household energy is used for other purposes excluding cooking, heating and lighting (Table 1.4). If we consider an extreme case of a poorly designed building with an excessive heating problem, the use _______________________________________________________________________________________________________________ Page: 16 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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of a fan with a power consumption of 220 Watts or that of an air-conditioning unit with a 1650 to 3300 Watts will definitely out-weigh the power consumption by the other consumer durables18. The house building fuel demand will be affected by the current building trends. This will be apparent if we sub-divide the energy for building into the energy that is used for producing, transporting and constructing buildings. If the trend is to build, say houses with materials that have to be transported from long distances and have used high energy inputs in the manufacturing process, then the total fuel demand will be much larger than a building with a low energy material19 which is locally available (Table 1.2).

Fig. 1.1:

The breakdown of fuel use into sectors according to energy content of the fuels used for Kenya.

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E.g. a T.V. has a power consumption of only 70 Watts. A 7 tonne lorry will use 3.29 KWh per km. _______________________________________________________________________________________________________________ Page: 17 of 145 19


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Fig. 1.2:

The total fuel cost of “house and home” including house building and durables for Kenya.

An analysis of the climate and current building trends for Kenya will shed light on ways of reducing the energy burden.

1.2 TROPICAL CONDITIONS: Almost all of the countries of the third world lie within the Tropics20 and experience climates in which the dominant building problem is providing protection from extreme heat21. Within Kenya, the range of climates is large and a discussion of all of them is not necessary for this study. I will concentrate on the coastal climates which are located between Latitude 2 and 4o South (Fig. 1.3 and 1.4). These areas are associated with annual mean temperatures of about 30oC and a minimum of about 23oC (Fig. 1.5). This condition is worsened by the humid air, with relative humidity readings of between 66 to 93% throughout the year22. The night ventilation of the building structure is less viable due to the slight daily range of temperature23. During the hottest month of April (Fig. 1.7), the maximum daily temperature was about 32oC (13.00 hours), while the minimum temperature was about 25oC (6.00 hours). 20

Between Latitude 23o North and 23o South. Spence and Cook: 1983. 22 Hooper: 1975. 23 Szokolay: 1981. _______________________________________________________________________________________________________________ Page: 18 of 145 21


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Fig. 1.3 & 1.4:

The maximum & minimum temperature distribution in Kenya.

Fig. 1.5:

The climatic data for Mombasa, Kenya.


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Table 1.3: Hourly air temperatures (T) and hourly solar radiation on a horizontal plane (SH) for Mombasa, during a typical day in April. Hours: 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

T (deg.C) 26.5 26.1 25.8 25.5 25.5 25.1 25.0 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30.0 29.1 28.1 27.5 27.2 27.0 26.9 26.6

a. SH (W/sq.m) 0 0 0 0 0 0 0 165 420 650 830 950 995 950 830 650 420 165 0 0 0 0 0 0

Symbol/Source: Hooper: 1975. a. Martin et al: 1971.


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Table 1.4:

1980 Kenya energy balance sheet (Million Giga-Joules).

Fig. 1.6:

Body heat exchange.


Yusuf H. Ebrahim


In order to establish the comfort limits for this climate, it is necessary to explain how the human body responds to its surrounding. The body temperature has to be maintained at around 37oC. This is done by regulating the bodily functions so as to balance the heat gain and loss by a corresponding opposite reaction. The body can loose heat through conduction24, convection25, radiation26 and evaporation27 (Fig. 1.6). Heat gains can be through metabolism28, conduction29, convection30 and radiation31 (Koenigsberger et al: 1978). The body will only be in a state of “thermal balance”, when the heat gain is equal to the heat loss.

Fig. 1.7:

Mean hourly temperatures for Mombasa.

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Contact with cold bodies. If the air is cooler than the skin. 26 To the night sky and cold surfaces. 27 Of moisture and sweat. 28 Basal and muscular. 29 Contact with warm bodies. 30 If the air is warmer than the skin. 31 From the sun, the sky and hot bodies. _______________________________________________________________________________________________________________ Page: 22 of 145 25


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Dr. J. Harris-bass32 identifies the 16 to 28oC air temperatures to be the comfort zone for a warmhumid climate. 30oC would necessitate air movement and sweating to maintain comfort. Plotting these on a day reading for Mombasa (Fig. 1.7), it becomes evident that outside thermal conditions under a shade are comfortable for most of the months except April. The peak external air temperature coincides with the peak solar radiation on a horizontal plane. In Mombasa, this happens at about 13.00 hours (Table 1.3). All the climatic information can be plotted on a bioclimatic chart (Fig. 1.8), which cab be used to predict the overall comfort conditions. The chart was developed by V. Olgyay and other workers, on which the comfort zone is defined in terms of the air temperature and the relative humidity, but subsequently it is shown by additional lines, how this comfort zone is pushed up by the presence of air movements and how it is lowered by radiation33.

Fig. 1.8:

Bioclimatic chart for men at sedentary work with Lamu (Kenya) annual temperature and relative humidity recordings for 06.00 and 12.00 GMT.

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Harris-bass, J: 1981. Koenigsberger et al: 1978. _______________________________________________________________________________________________________________ Page: 23 of 145 33


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A bioclimatic chart for Lamu (Kenyan coast) shows that a 0.1 to 0.4 m/s (metres per second) air movement is necessary to maintain comfort throughout the year (Fig. 1.8). This can easily be achieved by capturing the prevailing monsoon winds (Fig. 1.5) and the sea-breezes34. This assumes that the direct solar radiation and re-radiation from the heated building or other surfaces, has been excluded. A poorly designed roof which allows excessive heat to penetrate will raise the internal ceiling temperature and eventually the internal mean radiant temperature, to the extent that mechanical aids will be necessary to improve the air flow.

1.3 BUILDING TRENDS: One of the sad consequences of modernization was the destruction of the indigenous building form. A form that had taken a long time to be developed to suit the particular climate, social beliefs and technological capability. At the energy stand point, these buildings didn’t require any energy input to maintain comfort standards and because the materials were locally available and the building was done through community work, the energy input of the building material was also negligible.

Fig. 1.9:

A traditional Mijikenda homestead on the Coast of Kenya.

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Ebrahim: 1988. _______________________________________________________________________________________________________________ Page: 24 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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Fig. 1.10:

Section through a thatch roof.

The traditional house for the Mijikenda on the coast of Kenya is one such example (Fig. 1.9). The thatch roof and mud on wattle walls, were suited for the warm-humid climate. Due to the low angle of the driving rains35, the roof was considered as the primary building element and in some cases, the roof actually started from the ground, thereby avoiding the use of any walls. The thatch was made thick enough to withstand the high solar radiation and the interior of the buildings were cool because of the high ventilation rates due to the large eaves opening and the air penetration through the thatch (Fig. 1.10). A good thatch roof in many houses, often lasted for ten years and sometimes as many as sixty, but usually only because a fire was kept alight inside which deposited a layer of soot on the underside of the roof which discouraged insects. A thatch roof on a school or dairy building where no fire is kept burning will last a much shorter time36. Denyer also believes that the introduction of new building materials from Europe has changed the physical appearance of settlements more than anything else. Corrugated iron sheets and cement have had perhaps the greatest effect. The main attraction of corrugated iron roofs37 is that they are fireproof, and they were therefore quickly adopted in the residential areas which grew up around the new towns. Some of the buildings in the Old Town Mombasa have changed the original palm leaves roofs with corrugated iron sheets (Fig. 1.11). The thin corrugated iron sheets gives very little solar resistance and the high atmospheric salinity of the sea air corrodes the metal surface, turning it to a reddish-brown colour, which worsens the thermal performance38 (Fig. 1.12). 35

Mombasa received about 240 mm of rain during the month of May: Fig. 1.5. Denyer: 1978. 37 Or “Bati” or tin. 38 Hooper: 1975. _______________________________________________________________________________________________________________ Page: 25 of 145 36


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A corrugated iron sheet (CIS) will only last about 5 to 25 years and it requires regular maintenance. About 2% of the annual total imports for Kenya is steel alone. Approximately one quarter of this steel is used by the galvanized CIS industry. Thus, we can say that 0.5% of the country’s total imports are used in the manufacture of “Mabati”39. In 1983, mabati production cost Kenya Kshs. 280 million in foreign exchange40.

Fig. 1.11:

A street in Old Town Mombasa.

Fig. 1.12:

Section through a corrugated iron sheets roof.

39

The Kenyan name for galvanized CIS. Mwangi: 1986. _______________________________________________________________________________________________________________ Page: 26 of 145 40


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The use of cement in the latest residential buildings, in the form of concrete roof slabs has caused other thermal problems related to the time delay of solar penetration (Fig. 1.14). The thick solid slab delays the maximum air temperature and the maximum solar radiation which is at about 13.00 to 14.00 hours, so that maximum internal temperatures will be attained during the night. Many of these buildings show very little resemblance to the indigenous buildings (Fig. 1.13). But the demand for urban housing and the scarcity of supply compels the people to buy these houses even if they suspect that the performance standards have not been met. The projected urban housing requirement for Kenya during 1984 to 1988 was about 290,000 units, while the expected urban housing output for 1983 to 1984 was only 55,30441. The production of cement within Kenya has increased from 792 TMT (thousand metric tons) in 1970 to 1280 TMT in 1983 (United Nations: 1986). This has also increased the importation of fuels, because roughly half of the production costs of Kenyan cement is taken up by imported fuels in the manufacturing process42.

Fig. 1.13:

A modern developer built house in Mombasa.

41

Moi: 1984. Mwangi: 1986. _______________________________________________________________________________________________________________ Page: 27 of 145 42


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Fig. 1.14:

Section through a solid concrete slab.

Wealthy elite can escape the consequences of a poorly designed building through mechanical airconditioning. The others suffer from living conditions that permit neither efficient work nor rest or enjoyment43. This need not be the case, it is possible to create cities that have pleasant indoor and outdoor living spaces and are suited to the social conditions of their inhabitants. This can be done through research and implementation of the results. As Baker (1987) says: “Knowledge of building science assists us in adapting climatically responsive design, far more rapidly than the slow evolutionary approach of our forefathers”. As architects and engineers, “we have got to be able to convince our clients that architecture which responds to tradition, culture and climate is a far more suitable object of prestige”, than adopting the “international style” architecture.

43

Koenigsberger et al: 1978. _______________________________________________________________________________________________________________ Page: 28 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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1.4 ENVIRONMENTAL ROOF DESIGN FOR THE TROPICS: An understanding of the thermal processes taking place within the roof is essential for the appropriate choice and the design of roofs, especially for the tropics. An example of a simple roof consisting of a thin44 outer roof with a ceiling, will illustrate this point.

Fig. 1.15:

Section through a non-ventilated roof void.

Fig. 1.16:

Section through a ventilated roof void.

44

E.g. a corrugated iron sheet. _______________________________________________________________________________________________________________ Page: 29 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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Fig. 1.17:

Section through a ventilated roof void with a reflective foil base.

The incident solar radiation will have the effect of raising both the external surface temperature of the roof and the temperature of the void above ambient45. If the void is not ventilated (Fig. 1.15), the top surface of the ceiling will be heated by long-wave radiation, limited convective and conductive flow downwards. Depending on the thermal resistance of the ceiling46, the ceiling temperature will be elevated above ambient47. Convective and conductive down flows through the void can be eliminated by ventilating the void (Fig. 1.16). The temperature of the void will be almost the same as the ambient, due to the large ventilation rates, though the radiation transfer across the void will be almost unaltered. The radiative heat flow can be reduced by introducing a reflective foil on the top surface of the ceiling (Fig. 1.17). This reflects back most of the radiative heat flow and the void temperature will be almost the same as the ambient. It is important to bear in mind, that each addition of roofing material, will have a financial and energy implication. The latter is associated with both the energy input in the manufacturing, transporting and construction process, and the thermal performance which will have a direct influence on mechanical energy48, which will be the subject of the following chapters. 45

The temperature of the surrounding. See Chapter 2. 47 Baker: 1987. 48 In the form of air-conditioning. _______________________________________________________________________________________________________________ Page: 30 of 145 46


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1.5 CONCLUDING REMARKS: The scarcity of resources compels governments or individuals to choose between the various alternatives. Energy is limited to the supply49 and the demand50. If demand remains at the same level, while supply will inevitably decrease in the long-run, then the price of fuels will rise to such an extent that demand will eventually have to be reduced. This will cause unemployment and economic chaos51. An alternative is to gradually control the demand of fuels through increase of manufacturing efficiencies and reduction of energy wastes. In the construction and building industry, it implies the reduction of energy consumption at the manufacturing, transportation and construction levels. This should be done in collaboration with established thermal performance standards for buildings and especially the roof in tropical countries, so as to reduce energy consumption for maintaining comfort standards through the use of mechanical energy, i.e. air-conditioning.

49

Depending on production and innovation. Depending on consumption and conservation. 51 This is an outcome of inflation. _______________________________________________________________________________________________________________ Page: 31 of 145 50


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2.0 CHAPTER 2: CREATION OF A MODEL: _____________________________________________________________________ In order to evaluate the energy that is used as capital52, operating and maintenance energy53, it is essential to isolate a standard set of conditions that would be a fair representation of the actual life situation. The previous chapter had illustrated the diverse range of house forms in the warm-humid climate on the coast of Kenya. This chapter will attempt to develop a model that can be used to test different roofs in the next chapters.

2.1 ROOFS IN THE TROPICS: The role of the roofs in the tropics has been the topic of discussion for a long time and with due reason. In his previous work on the same subject, the author54 had isolated the roof as being the main building element which has a marked influence on the overall thermal performance of the house. It is the largest element in the house and must inevitably be the most expensive55. Due to the high altitude of the sun in the tropics and the recorded high levels of solar radiation56, it is not surprising that the roofs of buildings near the Equator will receive more solar radiation than any other surface of the building57. This may not be important in itself, but if we consider that about 80% of the total people in the tropics live directly under a roof58 and that most of these are also quite low59, it amplifies the importance of roof gains. The analysis of the heat flow through different types of roofs provides the theoretical framework for the practical study of the performance of materials and construction systems in the tropics60. In the future, similar wok should be done for the other elements of the building, namely the floors, walls and foundations. The countries of the warm humid tropics suffer from a lack of satisfactory roofing materials. The search for such a solution has been retarded by absence of performance standards for heat flow resistance61. Many of the developing countries don’t have any performance specifications for new materials and where these may exist, they are still in an infant stage. Kenya is the first country to develop a standard for fibre concrete tiles (FCT), though it is presently in the final stages of the 52

This includes the energy used in processing, transportation and constructional. i.e. Daily inputs in the form of heating or air-conditioning. 54 Ebrahim: 1987. 55 Spence and Cook: 1983. 56 Koenigsberger et al: 1978. 57 Petherbridge: 1974. 58 All houses in the rural areas are single storey buildings (Koenigsberger and Lynn: 1965). 59 Petherbridge: 1974. 60 Koenigsberger and Lynn: 1965. 61 Koenigsberger and Lynn: 1965. _______________________________________________________________________________________________________________ Page: 32 of 145 53


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draft form62. As will be shown later in this chapter, performance standards based on only resistance specifications is not enough to act as an effective energy conservation measure. Further more, the roof has to satisfy numerous other requirements such as noise and rain protection coupled by aesthetic appeal, which necessitates the use of multi-layers of different materials. Each of these will have different performance specifications, thus making it a specialized field of study.

2.2 CRITERIA FOR EVALUATION: Thumb rules have been used in the past as a quick way of checking whether performance standards have been met. This method of evaluation has the risk of over simplifying a problem and there is a danger that after a long period of use, these rules may be considered as the ultimate goal rather than a checking method. Such a wrong attitude will discourage further investigation into the phenomena and will create a disparity between theory and practical results. This observation will come to light as we try to establish suitable criteria for evaluating the thermal performance of roofs in warm-humid climates. The theory behind the methods of calculating such indices as the time lag of different elements63 and the comfort requirements for different climatic regions has been consistent in the history of environmental design. What is lacking is the revaluation of the application of the theory. In order to explain this point and also to clarify the methods that the author will use to evaluate the roofs in Chapter 4, the explanation of the following terms is necessary.

2.2.1 CONDUCTIVITY AND CONDUCTANCE: 64

Evans defines conductivity as the “rate at which a unit area of material of unit thickness will transmit heat from one surface to the other, when there is a unit difference in temperature between them”. Whilst conductivity is the property of a material, the conductance or “U” Value is the property of an element per unit surface area and will depend on the unit different in air temperature on the two sides65. It doesn’t consider the rate and source of the heat and for this reason; the “U” Value66 is mainly used in calculating other factors. Though in steady-state conditions67, maximum and minimum values can be sufficient. In 1971, the United Nations recommended a value of less or equal to 1.1 W/sq.m deg.C as one of the conditions to be satisfied by roofs in warm-humid climates68. The resistivity and resistance values are the reciprocal of the conductivity and conductance values respectively. 62

Mwangi: 1986. In our case, it is the roof. 64 Evans: 1980. 65 The unit of measurement is the Watt/sq.m deg.C. 66 And especially when we are only considering the air-to-air transmission. 67 Where the difference between the internal and external temperature is constant (Evans: 1980). 68 Spence and Cook: 1983. _______________________________________________________________________________________________________________ Page: 33 of 145 63


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2.2.2 SOLAR HEAT GAIN FACTOR (SHF): The “U” Value assumes that the solar energy striking the surface of the roof will be transmitted depending on the temperature difference. A closer look at the external surface will reveal another parameter to be considered. A large amount of solar radiation will be reflected back by the surface of the roof depending on the surface absorbance co-efficient and the surface conductance.

Fig. 2.1:

Definition of Solar Heat Gain Factor (SHF).

Fig. 2.2:

Surface conductance as a function of the wind speed.


Yusuf H. Ebrahim


A better measure of the energy gained by the structure is the solar heat gain factor (SHF). This can be defined as the heat flow through the construction due to solar radiation expressed as a fraction of the incident solar radiation69. For thin and homogeneous materials, the SHF can be calculated using the following equation: SHF =

Solar radiation transmitted through the roof = Incident Solar Radiation

a x U/Fo

Expressed as a percentage70 (Fig. 2.1). Where “a” is the absorbance co-efficient, “U” is the “U” Value and “Fo” is the Surface Conductance. Thus, the lower the value of “a” and “U”71, the lower the value of SHF. This can be done by using materials with a high surface reflectance. The surface conductance (Fo) is dependent on the texture of the surface and the wind speeds. A rough surface will hold large pockets of air compared to a smooth surface, thus increasing the surface conductance. The increase in wing speeds will also have an incremental effect on the surface conductance72 (Fig. 2.2). Most present day materials are heterogeneous in nature and are composed of numerous layers. Neither the above equation no other approximation curves can be used in this case. Intricate calculation methods are available, but these involve numerous tedious and in a sense, not an accurate way of finding out the SHF. It is here that computers have played a crucial part. Complex and repetitive calculations can be done in a short time, especially important when dealing with equations done in series. Where the answer of one equation is used as the input for another equation. The computer calculates both the total solar radiation incident on the roof and the total energy transmitted through the roof for a period exceeding 24 hours. Based on these two data, the SHF for different roofs can be calculated (Chapter 4). Koenigsberger73 recommends 4%, while Evans74 recommends 4.5% as the maximum SHF value for warm-humid climates. There is no doubt that a roof with a lower SHF value will perform better in the said climate, but there is a need to weigh the benefits against what the user can afford. Thus the limit proposed by Evans will apply to those with meager resources.

69

Koenigsberger et al: 1973. Koenigsberger et al: 1973. 71 But with a higher value of “Fo”. 72 Koenigsberger et al: 1978. 73 Koenigsberger et al: 1978. 74 Evans: 1980. _______________________________________________________________________________________________________________ Page: 35 of 145 70


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2.2.3 TIME-LAG: When calculating the SHF, the temperature difference between the interior and exterior surfaces is considered as an instantaneous transmission through the material without any heat storage effect75. Evans76 defines the thermal capacity as the amount of heat required to raise the temperature of a unit volume of the material by a unit difference in temperature. It can be calculated using the following formula: Thermal Capacity =

Volume x Density x Specific Heat.

The unit of measurement77 is the joules per deg.C. As the density and specific heat is increased the thermal capacity also increases and this has the effect of delaying the transmission of energy from the outer to the inner surface78. This delay in transmission of energy is called the “time-lag”79. The concept of time-lag has been present since the mid-sixties, though Dr. Baker and the author have now discovered an inconsistency in the method of measurement and application. In 1965, Koenigsberger and Lynn stated that “the exact calculation of the instantaneous flow of heat through a roof is complicated by the interaction of changes in ambient weather factors with the heat capacity of the structure”. To overcome this, they only tested roofs with low heat capacities and assumed a steady state condition. But by 1969, Givoni had concluded that under fluctuating conditions, “when the structure is heated and cooled periodically as a result of variations in outdoor temperature and solar radiation, or intermittent heating, the heat capacity has a decisive effect in determining indoor thermal conditions”. Steady state conditions are only applicable when the fluctuations of temperature do not exceed 3 deg.C absolute80. The climate under consideration has a temperature differential of 6.7 deg.C (see table 1.3) and thus, the time-lag under non-steady state conditions will have to be considered. In 1970, the Institute of Heating and Ventilating Engineers (IHVE)81, published graphs that could be used to estimate the time-lag of different materials (Fig. 2.3). These curves have been used by numerous writers, though the way that they calculated the time-lag for any building element was done differently. Koenigsberger (et al: 1978) considers the time-lag as the difference in time between the maximum daily external and the internal temperatures (Fig. 2.4). He doesn’t specify whether it is the external surface or external air temperatures or even whether the internal 75

i.e. The thermal capacity of the element is not considered. Evans: 1980. 77 Markus and Morris: 1980. 78 Petherbridge: 1974. 79 Evans: 1980. 80 Koenigsberger et al: 1978. 81 Martin: 1970. _______________________________________________________________________________________________________________ Page: 36 of 145 76


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temperature refers to the internal ceiling or air temperatures. What he does state is that the methods of calculating the time-lag are available, but that they are “rather involved and not well tested”. He again refers the reader to the IHVE Curves (Fig. 2.3).

Fig. 2.3:

Values of the time-lag (from IHVE Guide).

Fig. 2.4:

Koenigsberger et al (1978), defines the time-lag as the difference in time between the maximum daily external and internal temperatures.


Yusuf H. Ebrahim


Givoni (1969) had stated that it is important to consider both the effect of the external air temperature and the solar radiation. Markus and Morris (1980) explained the case where an increase in the internal temperatures could be achieved by either an increase in the external surface temperature82 or an increase in the external air temperature. This increased external air temperature which is producing the same internal temperature rise as was obtained with the solar radiation acting in conjunction with the actual external air temperature is termed as the sol-air temperature. Hence: Rate of heat flow due to sol-air temperature = Rate of heat flow due to solar radiation + Actual external air temperature. Evans (1980) uses the maximum estimated sol-air temperature and the maximum internal surface temperature83 to calculate the time-lag (fig. 2.5). Markus and Morris (1980) proposed a slightly different method. They used the peak sol-air temperature and the maximum rate of heat flow through the roof (Fig. 2.6). It is obvious that these three very different methods of calculating the time-lag make comparison of results almost impossible. Also, it would be questionable to calculate the time-lag by using two different units of measurements. Namely, the deg.C for the sol-air temperature and the Watts per square metre for the rate of heat flow.

Fig. 2.5:

Evans (1980) uses the maximum estimated sol-air temperature and the maximum internal surface temperature to calculate the time-lag.

82

Due to the effect of solar radiation. In our case, it would be the ceiling. _______________________________________________________________________________________________________________ Page: 38 of 145 83


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Fig. 2.6:

Markus and Morris (1980), use the maximum sol-air temperature and the maximum rate of heat flow for calculating the time-lag.

The author recommends an alternative method of calculating the time-lag. This method uses Markus and Morris (1980) definition though the peak sol-air temperature can be substituted by the maximum solar radiation. This conclusion was drawn after numerous consultations with my supervisor84 and by calculating the sol-air temperature of a simple roof structure (Appendix 4.8). The peak sol-air temperature coincides with the peak incident solar radiation and not with the peak external air temperature. The comfort upper and lower limits for the time-lag are less controversial. Evans (1980) felt that “a roof with time-lag of less than four hours will prevent the radiant heat gain from causing discomfort after 20.00 hours in the evening”. The United Nations recommends a time-lag of less than 3 hours for warm-humid regions85. Materials with time-lags exceeding 12 hours can also be used, since this will ensure that peak temperatures will be reached at about 24.00 – 3.00 hours (12 – 3 a.m.) when the user is already asleep. The critical sleeping time is between 21.00 – 24.—hours (9 – 12 p.m.). The house is unoccupied between 8.00 – 15.00 hours (8 a.m. to 5 p.m.) when the user is at work86. 84

Dr. N. Baker. Spence and Cook: 1983. 86 Ebrahim: 1987. _______________________________________________________________________________________________________________ Page: 39 of 145 85


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2.2.4 CEILING TEMPERATURE: Koenigsberger and Lynn (1965) recommended that the reflectivity and insulation should be selected so that the internal ceiling temperature should be selected so that the internal ceiling temperature should not be elevated more than 4.5 deg.C (40.1 deg.F) above the air temperature when the external surface is subject to solar radiation. They did not specify whether the air temperature refers to the external or internal air temperatures. In warm-humid climates, a freely ventilated building will have the internal temperatures as close to those found outside under the shade87. For this reason, the larger of the two temperatures88 should be the determinant.

2.3 SIMULATION WORK: In order to get a realistic result, it is important to simulate roofs under specific climatic conditions. Computers are pioneering in this field and are gaining popularity as they help to cut down on simulation time. A computer model called “FRED”, which was developed by Dr. N. Baker at the Martin Centre (University of Cambridge), is used to this end. FRED originated in 1979, when J. Manual at N.E. London Polytechnic wrote what was virtually a micro-computer version (for the PET) of McFarlane’s TEANET, then available on the Texas T159 programmable calculator89. Since than, Dr. Baker and the staff at the Martin Centre have made various modifications to FRED so as to make it compatible with the work at hand. FRED uses full annual weather data and runs on a BBC model B enhanced with a Torch Z80 second processor using Z80 Basic. This provides adequate memory and a little extra speed. The network is not set up automatically, but is defined by the user and can be tailored to suit the user’s immediate requirement. For purposes of simulating roofs in a warm-humid climate, Dr. Baker modified FRED, so that it could compute surface temperatures, air temperatures, internodal temperatures heat gain values. Each roof was defined according to different nodes (Fig. 2.7). A node is a point in space or surface which describes the essential properties of that material or space. In order to simplify the gathering of information, the author organized the nodes in series. In practice, this isn’t necessary, as the computer can work out the different energy paths, thus the nodes can be located in any order.

87

Baker: 1987. Either the external or internal temperature. 89 Baker: 1985. _______________________________________________________________________________________________________________ Page: 40 of 145 88


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Each node can be described according to the values of the capacitances (Appendix 4.1, 4.2 and 4.3), internodal conductance (Appendix 4.7) and ambient conductances (Appendix 4.1). The result of the simulation on different roofs is given in Chapter 4.

2.3.1 TEST CELL: FRED has to be fed with realistic building data. In order to do this, a hypothetical house was designed by the author. The plan (Fig. 2.8) and elevation (Fig. 2.9) resembles a similar house that was recently being sold by a developer in Mombasa (Fig. 1.13). It had a 71.3 square metre floor plan and was composed of two bedrooms, a living (dining) room and the utility areas.

Fig. 2.7:

Section through a hollow-pot slab showing the different layers and nodes.

Fig. 2.8 & 2.9:

Plan and North Elevation of the “Test House”.


Yusuf H. Ebrahim


The author considers the bedroom as being the most important space in the house. This conclusion is based on his own experience as a user of some of these buildings. During the working part of the day, the house is unoccupied, while the living room is only used for a short period during the evenings. Out of the 14 hours that the house is occupied (from 5 p.m. to 8 a.m.), 5 hours are used within the living room (from 5 p.m. to 10 p.m.), while 9 hours are used within the bedrooms (from 10 p.m. to 8 a.m.). The author also wanted to simulate the effect of the time-lag of different roofing materials and it was for these reason that he assumed that the bedroom was the space under consideration. FRED can be used to simulate any space and the results of the simulation wok within this study can be basis for analyzing other spaces. The bedroom under consideration was bedroom 1 (Fig. 2.8) and it had a floor area of 17.2 square metres. This bedroom will in this study be referred to as the “Test Cell” (Fig. 2.10).

2.3.2 CONCLUDING REMARKS: It is quite clear that roofs within the warm-humid climates have to be designed with a consciousness for the climate. The way that this can be done and the method of evaluating the effectiveness of the various choices is not so clear. There is still a scope in research for coordinating and up-dating the available information. Thermal indices such as the time-lag for different materials (e.g. the IHVE Curves) have to be up-graded according to the latest findings. Comfort requirements have to be validated on a regional scale. For the purpose of this study, the following is a summary of the thermal indices for a warm-humid climate: a). The conductance or “U” Value will be restricted to less or equal to 1.1 W/sq.m deg.C; b). The SHF should be less than 4.5%; c). The time-lag should be less than 4 hours, and d). The ceiling temperature should not rise higher than the internal ambient temperature in excess of 4.5 deg.C. The SHF will be calculated by dividing the solar radiation transmitted through the roof by the incident solar radiation and giving the answer as a percentage. The time-lag will be calculated using the method proposed by the author, i.e. by subtracting the peak solar radiation time from the time of maximum heat gain into the test cell. Energy used for manufacturing, transporting and constructing different roof forms and roofing materials, will be analyzed in the following chapter. _______________________________________________________________________________________________________________ Page: 42 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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Fig. 2.10:

Isometric of the house showing the test cell.


Yusuf H. Ebrahim


3.0 CHAPTER 3: CAPITAL ENERGY: _____________________________________________________________________ The economy of a country can be divided into various energy consuming sectors (Chapter 1). Each of these sectors makes a demand for energy supplies in the form of either high grade energy90 or low grade energy91. It is only fair for the governments of developing countries in particular, to ask how these sectors are going to use this energy and whether the sector is making the best use of the energy supply. The construction and material production sector of the economy uses its energy demand on the production, transportation and construction of different building elements. Gartner and Smith (1976) fell that it is “worthwhile to compare building methods with regards to their energy usage, because it is possible that significant energy savings can be made if energy-wasteful building methods can be identified and eliminated”. The production of building materials requires varying amounts of energy since some materials occur naturally and only require simple processing, while others are manufactured by energy intensive processes92. A typical balance of payments for a developing country is characterized by large importations of fossil fuels and manufactured goods93. The oil crises of 1973 opened the eyes of the world governments against taking the abundance of energy reserves for granted. A price policy was devised in Kenya to encourage users to reduce the consumption of fossil fuels. What is not so apparent is the “indirect importation” of these fuels into the country, through the importation of high energy consuming materials. In the last five years, numerous statements have been made about the high energy content in various imported materials94. It is feared that large importations of fossil fuels is being done in this way. There isn’t as yet a comprehensive of the energy input in building materials specifically related to developing countries95. This chapter is concerned with the energy used in constructing different roof forms, which can be termed as the capital energy. This can be done by considering the following: 1). Energy data in developing countries. 2). Material classification based on energy use. 90

High grade energy in the form of electricity, gas or fossil fuels. Low grade energy: Waste products such as the burning of fibres and organic matter. 92 Haseltine: 1975. 93 United Nations: 1986. 94 Gram (1984) and Mathu (1987). 95 Spence and Cook: 1983. _______________________________________________________________________________________________________________ Page: 44 of 145 91


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3). Energy to build different roof elements. 4). Total capital energy for different roofs. Haseltine believes that “it would be folly to put up a building that is economical in capital energy but extravagant in its running requirements”. In Chapter 4, consideration will be given to the thermal design of roofs in a warm-humid climate and how this will affect the running energy for the house. Table 3.0: Energy required to make, transport and place building materials: Material or product: High energy: Aluminium: Steel (structural) Glass Flat: Fibre-insulation: Fibre-reinforcement: Cement Rotary kilns: (U.K). Shaft kilns: Plastics PVC: Polystyrene: Polypropylene: Rubber: Natural: Synthetic: Recovered: Medium energy: Lime: Brick: Clamp: Trench (India) Hoffman (U.K.) Flettons: Concrete: Fibre conc. Tile: Reinforced: Precast:

Energy consumption MJ/kg Manufacture: Transport:

On-site:

Total:

258.7 31.5 12.5

1.0 0.3 0.3

0.2 0.2 0.2

7.7

0.3

-

260 32 13 b. 43 – 64 b. 38 – 56 8 a. 6 b. 67 – 92 b. 96 – 140 b. 108 – 113 b. 6 b. 139 b. 25

6.5 2.5 2.5 0.5 1.5

0.3 0.3 0.3 0.3 -

0.2 0.2 0.2 0.2 -

a. 3 – 5 a. 4 – 7 a. 2 – 3 a. 2 – 3 1 d. 1.5 b. 8 – 14 a. 1 – 8


Yusuf H. Ebrahim


Blocks: In situ: Soil cement block: Mortar mixed on site: Low energy: Timber Shuttering: Joinery: Sand Aggregate: Water: Fly ash, RHA, Volcanic ash: Soil:

3.0 1.4 0.24 1.3

0.3 -

0.2 0.2 0.2

a. 0.8 – 3.5 a. 0.8 – 1.6 d. 0.24 1.5

1.0 1.6 0.1 0.01

0.3 0.5 0.2 -

0.2 0.2 -

-

-

1.5 2.3 0.3 0.01 a. 0 – 0.3 a. 0 – 0.1

Symbol/Source: Haseltine, 1975. b. Chapman and Roberts, 1983. d. Auther (by calculation).

a. c.

Spence and Cook, 1983. Chapman, 1975.

Table 3.1: Energy required to make, transport and place building materials as a percentage of the overall energy consumption: Material or product:

High energy: Aluminium: Steel (structural) Glass Flat: Cement: Medium energy: Brick Clamp: Trench (India) Concrete Fibre Conc. Tiles: Blocks: In Situ: Soil Cement Block:

Energy consumption (%) Manufacture: Transport: On-site: 100km round trip:

Total:

99.5 98.4 94.6 96.3

0.4 0.9 2.3 3.7

0.1 0.7 3.1 -

100 100 100 100

92.9 83.3 100

4.3 10 -

2.8 6.7 -

100 100 100

85.7 87.5 100

8.6 -

5.7 12.5 -

100 100 100


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Mortar:

86.7

-

13.3

100

Low energy: Timber Shuttering: Joinery: Sand Aggregate:

66.7 69.6 33.3

20 21.7 66.7

13.3 8.7 -

100 100 100

3.1 ENERGY DATA IN DEVELOPING COUNTRIES: As has been stated earlier, information on the energy use in developing countries is scarce. This has made it necessary to modify information from the U.K. It is acceptable to do this provided the reader appreciates the assumptions made by the author. Spence and Cook (1983) found that modern factories will use less energy to manufacture a particular material compared to an older factory. Manufacturing machinery is expensive and for this reason, it takes time for factories in developing countries to replace older machinery, with the result that energy consumption may be higher. Spence and Cook (1983) go on to balance out this increase in energy consumption with a decrease due to the use of solar, human or low-grade energy. Table 3.0 gives the energy required to make, transport and place different building materials. It was compiled using information from different authors96. Energy data for a fibre concrete tile and a soil cement block was calculated by the author (Appendix 3.0 and 3.1). The unit of energy chosen is the Mega Joule per Kilogramme (MJ/kg). A conversion table is given in Appendix 1.0. It is also important to note that the above energy figures are referred to as “first order quantities”. These are fairly clear cut and can be obtained by interviewing manufacturers and other government bodies. Second and third order effects are not so obvious and which become progressively more difficult to identify. Fortunately, by definition they also influence the results less and less97. An example of the above is the fuel used by the employees of these factories for their own private use. This includes the energy used to house the employees, the provisions of services to educate, care for and feed them and their dependents. These are all expended to enable the particular person to play his part in the manufacture or use of that building product. All these “overhead” use of energy should not be included in the energy used in producing the building product. Chapman (1975) found that “if any part of the fuel consumed by people were counted as an input to the process then that quality of fuel would be double-counted in the analysis of the overall system”.

3.2 MATERIALS CLASSIFICATION BASED ON ENERGY USE: 96

Haseltine (1975), Spence and Cook (1983), Chapman and Roberts (1983) and Chapman (1975). Haseltine: 1975. _______________________________________________________________________________________________________________ Page: 47 of 145 97


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Spence and Cook (1983) classified different building materials into three categories depending on the overall energy use. By using the breakdown information from Haseltine’s work (1975) on the energy used for manufacture, transport and on-site assembly of the different building materials (Table 3.0), the following three categories can be identified:

3.2.1 HIGH ENERGY MATERIALS: These are materials which have an overall energy consumption value of more than 10 MJ/kg. It includes materials such as aluminium, synthetic insulation materials made of glass, plastics or rubber and cement based products. They are also characterized by high manufacturing energy inputs, accounting for about 94 – 99% of the total energy input (Table 3.1). Transport and on-site energy inputs are low accounting for about 0.1 – 1% of the total energy input. Aluminium has both the highest value of energy used in manufacturing and transporting the finished product. The high transport value of 1.0 MJ/kg is due to the low density of aluminium. Aluminium has a density of 2800 kg/cu.m while steel has a density of 7800 kg/cu.m (Clarke: 1979). The ratio of the two densities is approximately the same as the proportional increase in transport energy input (Table 3.0). For the purposes of this study, it was assumed that the materials or products have to be transported on average 50 km98. A more realistic picture will be obtained by actually calculating the relative distances that each material has to be transported and multiplying it with the volume, density and the energy used for transport (see Table 1.2: Chapter 1). In Kenya, aluminium and steel are imported from other overseas countries, thus the transport energy input will be much higher. Glass, cement, plastics and related products are manufactured within the country, though a substantial part of the raw material and machinery are imported. Rubber is imported from other countries, but the actual processing and assembly is done within Kenya. The implication of the above hasn’t as yet been investigated, in particular to developing countries. Haseltine (1975) estimated the on-site energy for a typical building, for which the total site energy for heating, lighting, transport, hoisting, mixing to completion of the structure, has been calculated and proportioned over the weights of materials used in the structure. In developing countries, the on-site energy input will be much lower than the stated figures. This is because a large amount of the work is done by using labour intensive methods. Since human energy has not been allowed for, there is an advantage in being under-mechanized99. Conventional methods of manufacturing cement are high energy consumers. These are normally large scale using rotary kiln method. Small-scale factories which use the shaft kiln method are still 98

With 50 km for return empty (Haseltine: 1975). Haseltine: 1975. _______________________________________________________________________________________________________________ Page: 48 of 145 99


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in an experimental stage in China and India100. Major energy savings can be made by substituting portions of the cement content by using lime and pozzolans, for mortars and plasters101. Discussions with Dr. R. Spence showed that countries like Kenya have large reserves of volcanic ash which can be used as pozzolans. High energy materials use high-grade fuels such as electricity, oil and pulverized coal in their manufacturing processes. In Kenya, most of the high-grade fuels102 are imported from other countries. Electricity is produced by harnessing the energy from rivers103. Hydro-electric power stations are more efficient compared to the other fuel-powered electric generators, though the distribution and secondary losses may be large (Chapter 1). Hydro-electric power stations involve the use of large water reservoirs. The latter have of late been the source of serious ecological and environmental problems104.

3.2.2 MEDIUM ENERGY MATERIALS: These are semi-processed materials including lime, brick and products made with low cement content (Table 3.0). Overall energy inputs range between 0.8 to 14 MJ/kg. Transport and on-site energy inputs are higher than the previous case, individually accounting for 3 to 14 percent of the overall energy input (Table 3.1). There is a large range of overall energy input for brick depending on the manufacturing process and the type of clay used. Flettons uses relatively little energy because the clay from which they are made contains carbonaceous material105. Soil cement blocks (SCB) have a low energy input because they are sun-dried and don’t use mechanical energy. SCB are also made on-site and thus, cut down on transportation costs. Other materials which have low cement content and have been mixed with a large amount of low energy input material will also fall within this category. Materials such as the concrete blocks, mortar and fibre concrete tiles have a large amount of sand which is a low energy material. Medium energy materials are usually also semi-processed materials. They can often use low-grade local fuels such as fibre wood, poor quality coal, bunker residue, or crop waste, and even some solar energy for drying processes, fuels which are more easily available and may even be

100

Spence: 1980a. Spence and Cook: 1983. 102 Except electricity. 103 Hydro-electric. 104 Gribbin: 1982. 105 Haseltine: 1975. _______________________________________________________________________________________________________________ Page: 49 of 145 101


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abundant106. In recent times, timber has become scarce in Kenya. At one time, soft woods such as pine and even cypress were not used for building purposes. But with the problems of deforestation and the rising demands for building woods, most of the timber and timber wastes107 which were used as fuels are now being used for building purposes.

3.2.3 LOW ENERGY MATERIALS: All naturally available materials will fall under this category, including different soils and aggregates, water and un-polished timber. Polished timber can only be classified after considering the energy used to shape, plane and sand the timber. Consideration should also be given to whether the timber is locally available or imported from other countries. Spence and Cook classify the latter as high-energy while the former as low-energy. All of the fuel timber of Kenya is locally available108. These materials are characterized by a high transport energy input (Table 3.0). Transport accounts for 66.7% of the total energy input for sand aggregates (Table 3.1), while manufacturing energy input only accounts for 33.3%. Labour intensive techniques are extensively used, while human energy is not considered and this accounts for the low manufacturing energy input. A nominal value of 0.01 MJ/kg for water is due to the filtration and distribution costs109. It is difficult to compare alternative building techniques y using Table 3.0, because 1 tonne of one material can never directly replace 1 tonne of another. For example, 1 tonne of aluminium will cover a greater area than 1 tonne of concrete. In order to provide a realistic appraisal, it is necessary to calculate the energy required to make more identifiable portions of a building.

3.3 ENERGY TO BUILD DIFFERENT ROOF ELEMENTS: Each of the materials in Table 3.0 can be used to construct different elements of the roof. The following five elements of the roof are identified as a means of comparing the energy inputs:

3.3.1 STRUCTURE: A roof structure is that part of the roof which transmits the loads to the walls or columns and there after to the ground. The roof structure has to be stable and should be able to resist the forces of climate and the other functional requirements. Each material has different structural strengths and relevant performance standards are used to determine the structure size and shape. For example, BS 8100 is used in the design of structural concrete. 106

Spence and Cook: 1983. E.g. Timber off-cuts and saw dust. 108 O’Keefe et al: 1984. 109 Haseltine: 1975. _______________________________________________________________________________________________________________ Page: 50 of 145 107


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The size of the structure is determined by the weight and volume of the other components of the roof110. Different roofing materials will require a determined size of structure. By using the “test cell” (Chapter 2) of a 3.85 m by 4.2 m room (Fig. 3.1), the area and volume of different materials can be calculated (Table 3.2, Column 1 and 2). This was than multiplied by the density (Column 3) and the result (Column 4) was multiplied by the relevant energy input (Column 5) to give the total energy required to build that element (Column 6). Table 3.2: Energy required for building different elements. Element: Area: (length/thickness) m sq.m Structure: S1. 4.2 m timber purlin: 0.01 (Fig. 3.3). S2. 4.2 m steel angle: c. 0.002 (Fig. 3.4). S3. 0.125 m thick 19.24 Concrete slab (Fig. 3.7). S4. 0.125 m thick 20.66 Concrete slab (Fig. 3.9). S5. reinforcement Steel bars for S3 (Fig. 3.7). S6. reinforcement Steel bars for S4 (Fig. 3.9). S7. 37.6 m total 0.003 Length of ceiling Timber battens (Fig. 3.14). S8. 39.8 m total 0.008 Length of timber rafters. S9. 74.7 m total 0.001 Length of timber roof battens. S10. 49.8 m total 0.001 Length of timber roof battens for R4. S11. 0.09 m thick 20.7 Concrete web with 0.075 m

Volume:

Density:

Weight:

cu.m

kg/cu.m

kg

Energy: Total: Cons. Energy cons. MJ/kg MJ

0.042

a. 419

17.6

b. 2.3

40.48

0.008

a. 7800

c. 62.4

b. 32

1996.8

2.41

a. 2100

5061

b. 11

55671

2.58

a. 2100

5418

b. 11

59598

g. 0.012

a. 7800

93.6

b. 32

2995

g. 0.013

a. 7800

101.4

b. 32

3245

0.113

a. 419

47.4

b. 2.3

109

0.32

a. 419

134.1

b. 2.3

308.4

0.08

a. 419

33.5

b. 2.3

77.1

0.05

a. 419

21

b. 2.3

48.3

1.97

a. 2100

4137

b. 11

45507

110

Including the structure itself. _______________________________________________________________________________________________________________ Page: 51 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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Wide concrete fins. S12. reinforcement Steel bars for S11.

g. 0.013

a. 7800

103

b. 32

3295

Symbol/Source: Author (by calculation). a. Clarke: 1979. b. See Table 3.0 c. Allwood et al: 1975 d. Average figures (See Table 3.0). e. Bullard: 1987 (F.C. Tiles have a similar shape to clay pantiles though it differs in length and thickness. f. No energy figures available. g. BS.8110 (The area of reinforcement in each direction should not be less than 0.24% of bh for slabs and 0.15% of bh for beams).

Fig. 3.1 & 3.2:

Showing the length and position of the purlin.

Fig. 3.3 & 3.4:

Showing the size of the timber purlin and steel angle.

Fig. 3.5 & 3.6:

Showing the area and length of the concrete roof slab.


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Table 3.2 gives the energy required to build different roof structures. A comparison of the total energy consumed (Column 6) reveals the following: (a) A 4.2 m steel angle (S2) uses approximately 50 times more energy compared to the same length of timber (S1) (Fig. 3.2, 3.3 & 3.4). This is because steel is denser and has a high energy input per kilogramme (Table 3.0). (b) A concrete slab111 has the largest overall energy input (S4) (Fig. 3.6 & 3.7). The large weight of the concrete slabs (Table 3.2, Column 4) and the large energy per kilogramme exceeds the values associated with steel (S2). The same applies for S2 and S11. An increase in the pitch of the roof has the effect of increasing the area and eventually, the weight of the concrete slab (Fig. 3.8 & 3.9). This is the cause of the difference between S2 (which is the structure for a low-pitch concrete tile) and S3 (a higher pitch clay tile). (c) All materials which are made of steel are subject to high energy inputs. The reinforcement bars S5, S6 and S12, have small weights but large overall energy inputs. (d) Timber elements are bulky, but they have a low density and low energy per kilogramme. S7, S8, S9 and S10 have low total energy inputs. Table 3.2: Energy required for building different elements. Element: Area: Volume: (length/thickness) m sq.m cu.m Roofing: R1. 0.001 m thick 60.8 0.06 Corrugated iron sheets. R2. 0.012 m thick 44.8 0.54 Clay pantiles. R3. 0.012 m thick 44.8 0.54 Concrete coloured pantiles. R4. 0.006 m thick e. 43.3 0.26 Fibre concrete tiles (Pantiles). R5. 0.03 m thick 20.7 0.62 Concrete paving slabs for S11 (Fig. 3.18).

Density:

Weight:

kg/cu.m

kg


a. 7800

475.8

b. 32

15226

a. 1900

1026

d. 4

4104

a. 2100

1134

d. 2.2

2495

1818.2

472.7

b. 1.5

709.1

a. 2100

1302

d. 2.2

2864

111

Without even including the reinforcement. _______________________________________________________________________________________________________________ Page: 53 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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R6. 0.003 m thick Bitumen felts for S11.

Fig. 3.7:

20.7

0.06

a. 1700

102

d. 47

4794

Showing the thickness of the concrete slab.

Fig. 3.8 & 3.9:

Showing the length and thickness of the concrete roof slab.

Fig. 3.10 & 3.11: Showing the length and area of the roofing material. _______________________________________________________________________________________________________________ Page: 54 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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3.3.2 ROOFING: The exterior material of the roof which protects the structure and the building interior would fall under this category. Six types of roofing materials and the overall energy inputs are given in Table 3.3. The following is the highlight of the results: (a) Roofing materials made of steel and bitumen felts had large overall energy inputs, due to the high energy per kilogramme associated with such materials (R1 and R6). (b) Fibre concrete tiles (R4) had the lowest overall energy input. Infact, 96% less energy was used for building them compared to a corrugated iron sheet (R1). (c) Given the same volume of clay (R2) and concrete (R3) tiles, the latter will be built with approximately 1.5 times less energy.

3.3.3 CEILING: The internal membrane of the roof is referred to as the ceiling. Three types of ceilings which may be fixed on the different roof structures are given in Table 3.4. A comparison of the overall energy inputs reveals the following: (a) A clay blocks ceiling (C3) has the largest overall energy input. This is due to the great volume and density of the material which results in a large weight which when multiplied by even a small energy per kilogramme will result in a large overall energy input. (b) A fibre insulation ceiling (C1) uses approximately 3 times less energy when compared to a clay block ceiling. (c) A low pitch roof has a smaller volume and thereby a smaller weight compared to a high pitch roof. This results in a reduction of the overall energy input. Ceiling C1 uses 160 MJ less than C2.

3.3.4 FINISHES: This is the actual surface treatment of either the roofing or ceiling. Table 3.4 gives three possible finishes that can be applied to a concrete surface. Painting and maintenance values have been considered due to the lack of the relevant energy data. An analysis of the table is given below:


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(a) A plaster finish (F3) has the lowest overall energy input, even though it has the highest energy per kilogramme value. This is because of the low volume and low density of plaster compared to screed (F1). (b) A screed finish (F2) has a large overall energy input because of the large volume and large density of the material. (c) A slight decrease in the thickness of the screed will result in a large decrease in the overall energy input. A 0.01 m (10 mm) decrease in the thickness of the screed112 will result in about 200 MJ savings113. Table 3.4: Energy required for building different elements. Element: Area: (length/thickness) m sq.m Ceiling: C1. 0.012 m thick 17.2 Fibre-insulation on Low pitch roof. C2. 0.012 m thick 18.6 Fibre-insulation on High pitch roof. C3. 0.025 m thick Clay hollow blocks for S11. Finishes: F1. 0.02 m thick Screed to lay R5. F2. 0.03 m thick Screed to lay R6. F3. 0.012 m thick Plaster for C3. Extras: E1. 0.05 m thick

Volume:

Density:

Weight:

cu.m

kg/cu.m

kg


0.21

a. 300

63

d. 53.5

3371

0.22

a. 300

66

d. 53.5

3531

1.38

a. 1900

2622

d. 4

10488

20.7

0.41

a. 1200

492

b. 0.8

394

20.7

0.62

a. 1200

744

b. 0.8

595

18.6

0.22

a. 600

132

b. 1.5

198

12.4

0.62

a.25

15.5

d.118

1829

112

The difference between F2 and F1. Approximately 1.5 times less energy. _______________________________________________________________________________________________________________ Page: 56 of 145 113


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Polystyrene insulation for C3. E2. reflective foil 12.4 Lining for C3.

f.

Symbol/Source: Author (by calculation). a. Clarke: 1979. b. See Table 3.0 c. Allwood et al: 1975 d. Average figures (See Table 3.0). e. Bullard: 1987 (F.C. Tiles have a similar shape to clay pantiles though it differs in length and thickness. f. No energy figures available. g. BS.8110 (The area of reinforcement in each direction should not be less than 0.24% of bh for slabs and 0.15% of bh for beams). Table 3.5: Total capital energy for different roof types. Roof description:

Total energy consumption (MJ). Structure: Roofing: Ceiling: S1 + S7 R1 C1 149.5 15226 3371

ROOF 3.1: Corrugated iron sheets On timber purlins with Fibre-insulation ceiling on Timber structure (Fig. 3.16). ROOF 3.2: S8 + S9 Clay pantiles on timber 385.5 Structure with fibreInsulation ceiling. ROOF 3.3: S8 + S9 Concrete coloured b. 386 Pantiles on timber Structure with fibre-insulation Ceiling (Fig. 3.18). ROOF 3.4: S8 + S9 Fibre concrete tiles b. 386 On timber structure with Fibre-insulation ceiling. ROOF 3.5: S4 + S6 Fibre concrete tiles + S10

Finishes: a.

Extras:

Total: T1 18747

R2 4104

C2 3531

T2 8021

R3 2495

C2 3531

T3 6411

R4 709

C2 3531

T4 4626

R4

F3

T5


Yusuf H. Ebrahim


With battens on concrete 62891 709 Pitch slab with plastered finish. ROOF 3.6: S11 + S12 R5 + R6 Paving slabs on bedding Screed on bitumen felts 48802 7658 On screed on hollow pot Slab with polystyrene insulation In ventilated cavity and a plastered Ceiling (Fig. 3.21).

198 C3 10488

F1 + F2 + F3 1187

63798 E1

T6

1829

69964

Notes: a. Painting and maintenance values have not been considered. b. Minimum structural values were considered.

Fig. 3.12 & 3.13: Details of different roof structures and materials.

Fig. 3.14 & 3.15: Showing the length and area of the ceiling.

Fig. 3.16 & 3.17: Details of different ceilings. _______________________________________________________________________________________________________________ Page: 58 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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3.3.5 EXTRAS: These are all the other items which contribute to the overall performance of the roof. Energy data were only available for the polystyrene insulation (Table 3.4: E1).

3.4 TOTAL CAPITAL ENERGY FOR DIFFERENT ROOFS: All the previously discussed roof elements can be used in various combinations to achieve the desired results. Table 3.5 gives six such combinations together with the total capital energy values. The following is an analysis of it: (a) The hollow-pot slab with various roof modifications (Roof 3.6) had the largest overall energy input (Fig. 3.21). This was due to the large energy input by the structure (S11 and S12), roofing (R5 and R6) and the ceiling (C3). (b) A fibre concrete tile roof (Roof 3.4) had the lowest energy input. This can be improved even further by using an alternative ceiling which has a low energy input114. (c) The benefits of a fibre concrete tile (FCT) can be negligible if a high energy structure is used. An FCT roof on a concrete pitched slab has the second largest energy input, with the structure accounting for 99% of the total energy input. (d) A corrugated iron sheet (CIS) roofing (Roof 3.1) is a high energy material (Fig. 3.16 & 3.17). It uses approximately 75% more energy compared to a FCT roof (Roof 3.4) and 65% more energy compared to a concrete coloured pantile roof (Roof 3.3). (e) A concrete coloured pantile roof (Roof 3.3) uses approximately 20% less energy compared to a clay pantile roof (Roof 3.2) (Fig. 3.18).

Fig. 3.18 & 3.19: Section through different roofs. 114

A fibre insulation ceiling (C2) accounts for 76% of the overall energy input. _______________________________________________________________________________________________________________ Page: 59 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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Fig. 3.20 & 3.21: Sections through a hollow-pot slab.

3.4.1 CONCLUDING REMARKS: The purpose of analyzing the energy input of various building materials is to evaluate the ways that societies use fuel and identify possible strategies that can be employed to save energy. Any savings can be traced back to savings in actual fuels used, as energy can be transformed from one form to another. This can help planners to answer such questions such as “do we need more fuel supplies? And if so, who needs them and for what purpose? (Chapman: 1975). Fuel costs account for a large proportion of the overall cost of a material and so an energy-efficient solution will usually be a cheap solution also115. In the long-term, the price of fuels may rise over and above the other resources such as labour, thereby affecting the cost of materials. Thus, there is a need for long-term planning of fuels inputs in materials. A fibre concrete roof and structure had the lowest total energy input compared to the other five roofs analyzed in this chapter. This was due to the use of labour intensive methods of production and the use of locally available materials. It is important to evaluate the inputs against the possible benefits. All the energy used in production, transportation and construction of materials, must be weighed against the energy saved in maintaining a comfortable interior of a building. The latter is a function of the thermal performance of the building fabric116 and this will be the subject of the next chapter. An analysis of both the capital and operating energy and ways of choosing an appropriate material for a particular climate will be done in Chapter 5. 115

Spence and Cook: 1983. In our case, it is the roof. _______________________________________________________________________________________________________________ Page: 60 of 145 116


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4.0 CHAPTER 4: OPERATING ENERGY: _______________________________________________________________________________ The energy used to manufacture, transport and construct different roofing materials was analyzed in the last chapter. This chapter will deal with the thermal performance of different roofing materials and its effect on the internal comfort conditions. The choice of roofing material will have a direct implication on the overall energy requirement of the house in the form of the airconditioning or cooling costs. “What did people do to stay cool before the advent of air-conditioning?” H. Strauss (1980) asked this question in his article on passive cooling in warm-humid climates. Developing countries have to address themselves to this question. Most traditional buildings were adaptable to the local climate, whereas modern buildings fail to perform as well and resort to mechanical aids to mend a design deficiency. This could be attributed to two main factors. Firstly, there isn’t enough research done on new or intermediate materials, with the aim of modifying them to suit the specific climatic requirements. So the problem of an inappropriate transfer of technology from the developed to the less developed countries is taking place117. Secondly, there is no attempt to integrate the new technologies within the social fabric. Traditional technologies were very successful because they were acceptable to the society. There was a sense of dignity and pride for the old materials118. Modernization has destroyed this attitude to the old building trades without creating a sense of judgment for the right choice of new materials. Thus, roofing materials such as galvanized corrugated iron sheets (GCI) are seen as superior compared to the traditional thatch roofs. It may be argued that the latter has shown some weaknesses when used in the urban settings, but this does not have to deter its use in other situations. Other materials such as the fibre concrete tiles (FCT) have not made a big impact on the local construction market, because of the lack of a proper information network. In order to restore the dignity for FCT and other intermediate materials, it is necessary to conduct tests which will prove the overall superior quality of the material. This chapter will try to do this in its own humble way.

4.1 EFFECTIVE SURFACE AREA AND SOLAR EXPOSURE: Traditional buildings are a source of immense information. V. Gupta (1987) conducted a study on a medieval Indian town of Jaisalmer. He noticed that the entire façade of the Jaisalmer House was composed of intricate fins which increased the surface area many times. With the backing of other 117

Ebrahim: 1988. Denyer: 1978. _______________________________________________________________________________________________________________ Page: 61 of 145 118


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computer simulations on the same subject, he concluded that fruitful results will be achieved by choosing a built form with a low solar exposure and by trying to increase its surface area. This principle can be applied to the design of roofs in warm-humid climates. A thin exterior roof with a ceiling has the effect of increasing the surface area while ensuring that the interior ceiling is shaded. The thermal performance of the roof can be improved by ventilating the cavity in-between the two membranes (Fig. 1.16). As early as 1923, this principle was being applied by Mrs. Carolyn Smith119 in her house in Birmingham (Fig. 4.1). Birmingham has a nineteen hundred cooling degree day season and thus, the cooling strategy for this house could be used in warm-humid regions. In 1923, the recommended ratio of attic ventilation to the area of the floor below it was one to four hundred. Mrs. Smith used instead a ratio of one to forty for her gable and vents. The efficiency of the attic exhaust component was improved by the dormer windows and the mid wall vents. This addition brought the effective ratio to one to twenty. In the words of Mrs. Smith: “It always works to follow ….. such principles as hot air rises and cold air falls. After all, why should I use fans and air-conditioning when nature will do the job for me. That’s only common sense and it would be a shame to waste” (Strauss: 1980).

Fig. 4.1:

Section through Mrs. Smith’s House showing the passive cooling techniques.

119

Strauss: 1980. _______________________________________________________________________________________________________________ Page: 62 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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Fig. 4.2:

Section through a hollow-pot slab.

Concrete structures have been gaining popularity in many developing countries without any basis for its climatic appropriateness. In an attempt to develop a concrete structure that can satisfy thermal requirements in warm-humid climates, Dr. Baker and the author devised a hypothetical hollow-pot slab with a ventilated cavity and exterior reflective finish (Fig. 4.2) (Ebrahim: 1987). There was also a possibility of improving the performance by adding an insulation lining (Fig. 4.3) or reflective lining (Fig. 4.4). It is not possible to predict the effectiveness of this type of roof by using steady state calculations or prediction curves120. This is where computers can be used to simulate such roofs and the experience can be used to predict other similar conditions.

4.2 ROOFING MATERIALS: The simulation model “FRED” described in Chapter 2.3 is used to simulate two main roofs, namely, a hollow-pot slab with various modifications (Roof 4.1, Fig. 4.5) and a fibre concrete tile (FCT) roof with similar modifications (Roof 4.2, Fig. 4.6). A solid concrete slab (Roof 4.3, Fig. 4.7) is also simulated, so as to compare the results with those of the other two roofs. Table 4.0 gives the description of the different roof configurations that were tested. Owing to the programming procedure of FRED, it was easier for the author to start simulating the roofs with all the essential ingredients121 and successively remove these roofing materials with each simulation. Thus, Roof 4.1 will have more roofing layers compared to roof 4.1A. Similarly, Roof 4.2 is more comprehensive than Roof 4.2A. 120

Ebrahim: 1987. Namely, the reflective exterior finish, an insulated lining, a ventilated cavity and a recommended material thickness. _______________________________________________________________________________________________________________ Page: 63 of 145 121


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Fig.4.3 & 4.4:

Hollow-pot block with insulation lining or reflective lining.

Fig 4.5 & 4.6: A hollow-pot slab and a fibre concrete tile roof with various modifications (Roof 4.1 and Roof 4.2). _______________________________________________________________________________________________________________ Page: 64 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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FRED was used to predict the following temperatures: (a) The exterior surface temperatures, (b) The surface temperatures of the different roofing layers (referred to as nodes), (c) The ceiling temperatures, and (d) The internal ambient temperatures. All these temperatures were plotted on graphs for individual roofs and this can be used for purposes of comparison (Also see Appendix 4.9 to 4.28). FRED also calculates the total incident solar radiation and the amount of heat that is transmitted through the different roofs for a period of five typical days (Table 4.1 to 4.4). This information is used to calculate the solar heat gain factor (SHF) and the time-lag (Table 4.5). Table 4.0: Description of different roof configurations. Roof type: Description: Roof 4.1: Hollow pot slab and varies modifications. 4.1 30 mm paving slabs on 20 mm bedding screed on bitumen felts on 30 mm screed on 240 mm hollow pot slab with 50 mm polystyrene insulation in the hollow pots and 12 mm interior plaster. 4.1A Same as 4.1, but with a reflective exterior finish. 4.1B Same as 4.1A, but without the polystyrene insulation. 4.1C Same as 4.1B, but without the exterior paving slabs. 4.1D Same as 4.1C, but without the top bedding screed. 4.1E Same as 4.1D, but without the ventilating cavity. This is the equivalence of a solid slab with brick infill. 4.1F Exterior reflective finish on bitumen felts on 30 mm bedding screed on 90 mm solid concrete slab with 12 mm interior plaster. 4.1G Same as 4.1F, but with reduced reflective exterior finish. Roof 4.2: 4.2 4.2A 4.2B 4.2C 4.2D

Fibre concrete tiles on timber structure. Fibre concrete tiles with interior fibre-insulation board and 150 mm ventilation cavity. Same as 4.2, but with a reflective exterior finish. Same as 4.2A, but with a 100 mm ventilation cavity. Same as 4.2B, but with a 50 mm ventilated cavity. Fibre concrete tiles with reflective exterior finish and fibre-insulation bard interior finish.


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4.2E 4.2F

Same as 4.2D, but without the interior fibre-insulation board. Same as 4.2E, but with a reduced reflective exterior finish.

Roof 4.3: 4.3 4.3A 4.3B 4.3C 4.3D

Solid slab. 300 mm solid concrete slab. Same as 4.3, but with a reflective exterior finish. 191 mm solid concrete slab with a reflective exterior finish. 82 mm solid concrete slab with a reflective exterior finish. Same as 4.3C, but with a reduced reflective exterior finish.

The results of the simulation work on the different roofs and the various modifications can be analyzed by looking at the effect of the following: (a) The integrated design, (b) The reflective exterior finish, (c) The insulation lining, (d) The thickness of various materials, and (e) The ventilated cavity, And analyzing their influence on the following thermal design parameters:

4.3 CEILING TEMPERATURE AND COMFORT REQUIREMENTS: The ceiling temperature should not exceed the internal ambient temperature in excess of 4.5 deg.C122, equally the internal ambient temperature should be between 16 – 28oC (Chapter 1). Otherwise, if the internal ambient temperature exceeds 30oC123, than some air movement or sweating will be necessary to maintain comfort levels. Air movement can be achieved by either passive124 or active125 methods. The latter carries an energy value and should only be used as a last resort. The following is the effect of various roof modifications on the ceiling and comfort requirements:

4.3.1 INTEGRATED DESIGN: If we compare Roof 4.1 (Fig. 4.8) with Roof 4.2 (Fig. 4.16) and Roof 4.3 (Fig. 4.23), the following may be observed: 122

Koenigsberger and Lynn: 1965. Note that the unit for temperature is oC while the difference in temperature is deg.C. 124 Using natural ventilation methods. 125 Using air-conditioning. _______________________________________________________________________________________________________________ Page: 66 of 145 123


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(a) All three roofs have a high external surface temperature with the peak temperature coinciding with peak external incident solar radiation (14.00 hours). This is because the external surface is made of a cement base which has a high surface absorptivity. (b) Roof 4.1 and Roof 4.3 have a similar distribution of nodal temperatures with the peak of the external surface temperature, the concrete nodal temperature and the ceiling temperatures showing a continuous shift in time. All the above temperatures are centralized around the 14.50 hour in the case of roof 4.2 (Fig. 4.16). This shows an instantaneous transmission of heat in the case of Roof 4.2, while there is a time-lag in the other two roofs. (c) Roof 4.1 has ceiling temperatures that are lower than the internal ambient temperatures, while Roof 4.3126 has the worst performance with temperature differences in excess of the 4.5 deg.C recommendation. At 15.00 hours, Roof 4.2 had a 2 deg.C difference (Fig. 4.16). This reduction in ceiling temperatures is due to the ventilated cavity. (d) Roof 4.1 had a much lower internal ambient temperature compared to the other two roofs. (e) Between 1.00 to 8.00 hours and between 20.00 to 24.00 hours, the temperatures of the different nodes for Roof 4.2 were approximately the same with the external ambient temperature 8.00 to 20.00 hours; there was a sudden rise in temperatures (Fig. 4.16). In the case of Roof 4.3, the temperatures were always higher than the external ambient temperature except during 10.00 to 14.00 hours; when the temperatures were lower (Fig. 4.23).

Fig. 4.7:

A solid concrete slab (Roof 4.3).

126

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Fig. 4.8:

A hollow-pot slab with exterior paving slabs, a ventilated cavity and an insulated lining.

Fig. 4.9:

A hollow-pot slab with reflective exterior, a ventilated cavity and an insulated lining.


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Fig. 4.10:

A hollow-pot slab with a reflective exterior finish and a ventilated cavity.

Fig. 4.11:

A hollow-pot slab with a reflective exterior finish and ventilated cavity (without the exterior paving slabs).


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Fig. 4.12:

A hollow-pot slab with a reflective exterior finish and ventilated cavity (but without the exterior paving slabs and screed).

Fig. 4.13:

A solid concrete slab with brick infill.


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Fig. 4.14:

90 mm solid concrete slab with a reflective exterior finish.

4.3.2 REFLECTIVE EXTERIOR FINISH: Compare Roof 4.1A (Fig. 4.9), Roof 4.2A (Fig. 4.17) and Roof 4.3A (Fig. 4.24) with the previous roofs. A reflective exterior finish has the following implications: (a) All the three external surface temperatures have been reduced depending on the external surface absorptivity. (b) All the three roofs show a decrease in the magnitude of nodal temperatures, though the distribution of temperatures has remained the same. The nodal temperatures are centered around the 14.50 hour for Roof 4.2A, while Roof 4.1A and Roof 4.3A show a shift in the peak time. (c) Ceiling temperatures are lower than before and in the case of roof 4.3A, the temperature difference is now acceptable. (d) There is a slight decrease in the internal ambient temperature for Roof 4.1A, while Roof 4.2A and Roof 4.3A have shown no change in the internal ambient temperature. _______________________________________________________________________________________________________________ Page: 71 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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(e) Thin concrete slabs are more responsive to a change in the reflective exterior finish compared to a thick slab. By comparing Roof 4.3C (Fig. 4.26) with Roof 4.3D (Fig. 4.27), an increment in the external surface absorptivity of a 82 mm solid concrete slab will cause a large increase in both the internal ambient temperature and the ceiling temperature. A similar observation is possible when comparing Roof 4.1F (Fig. 4.14) and Roof 4.1G (Fig. 4.15). (f) In the case of thin membranes such as the fibre concrete tiles (FCT) without any ceiling127, the ceiling temperature, and the external surface temperatures are approximately the same. An increase in the absorptivity of the external surface128 will increase the ceiling temperatures to discomfort levels.

Fig. 4.15:

90 mm solid concrete slab without the reflective exterior finish.

127

The underside of the roof. Compare Roof 4.2E (Fig. 4.21) and Roof 4.2F (Fig. 4.22). _______________________________________________________________________________________________________________ Page: 72 of 145 128


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Fig. 4.16:

Fibre concrete tiles with a interior fibre insulation ceiling and 150 mm ventilated cavity.

Fig. 4.17:

Fibre concrete tiles with a fibre insulation ceiling, 150 mm ventilated cavity and reflective exterior finish.


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Fig. 4.18:

Fibre concrete tiles with a insulation ceiling, 100 mm ventilated cavity and exterior reflective finish.

4.3.3 INSULATION LINING: In the case of a pitched roof with fibre concrete tiles, the removal of the fibre insulation ceiling129 will have the following implications: (a) The ceiling temperatures will rise to the extent that there will be no difference with the external surface temperatures. (b) The difference between the ceiling temperature and the internal ambient temperature is greater in the case of the roof without a ceiling (Roof 4.2E, Fig. 4.21) compared to the roof with a ceiling (Roof 4.2D, Fig. 4.20). In fact, the former has a difference exceeding the 4.5 deg.C recommendation. (c) The internal ambient temperature in higher in Roof 4.2E (Fig. 4.21) than in Roof 4.2D (Fig. 4.20).

129

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Due to the location of the internal insulation lining within the hollow-pot slab (Roof 4.1A, Fig. 4.9), the removal of which (Roof 4.1B, Fig. 4.10) will cause no change in the external surface temperature, concrete node temperature and void temperature. Both the ceiling and internal ambient temperatures are lower in the case of the roof without the insulation lining (Fig. 4.10), thus, the insulation has actually worsen the internal comfort conditions.

Fig. 4.19:

Fibre concrete tiles with a insulation ceiling, 50 mm ventilated cavity and exterior reflective finish.

Fig. 4.20:

Fibre concrete tiles with a fibre insulation ceiling.


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Fig. 4.21:

Fibre concrete tiles without a ceiling.

Fig. 4.22:

Fibre concrete tiles without a ceiling and no exterior reflective finish.


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4.3.4 THICKNESS OF VARIOUS MATERIALS: The removal of the external paving slabs (Roof 4.1C, Fig. 4.11), the screed (Roof 4.1D, Fig. 4.12) and the brick infill (Roof 4.1F, Fig. 4.14), will have a mild effect on the performance of the hollowpot slab. This is because all these materials are thin and are made of a concrete or brick base which have a relatively high conductance value. The thermal performance of the solid concrete slab becomes retrogressively worse with a decrease in the slab thickness. A 300 mm solid concrete slab (Roof 4.3A, Fig. 4.24) will have a lower ceiling and internal ambient temperature compared to the 191 mm slab (Roof 4.3B, Fig. 4.25) and the 82 mm slab (Roof 4.3C, Fig. 4.26). Though, the shift in peak temperatures is lowest in the 82 mm slab (L1 = 0.5 hours) and highest in the 300 mm slab (L1 = 1.5 hours).

4.3.5 VENTILATED CAVITY: If we compare the thermal performance of a hollow-pot slab (Roof 4.1D, Fig. 4.12) and a solid concrete slab with brick infill (Roof 4.1E, Fig. 4.13), so as to illustrate the importance of the ventilated cavity. In the case of the hollow-pot slab (Fig. 4.12), the ceiling temperatures are lower than the internal ambient temperature, which is also lower than the external ambient temperature. Thus, the building is cooler than conditions even under the shade. The removal of the ventilated cavity will cause both the ceiling and internal ambient temperatures to rise. This effect of the ventilated cavity on the ceiling and internal ambient temperature can be illustrated further, by comparing the effect of decreasing the ventilated cavity. There is a retrogressive change in the thermal performance of the roof with a progressive decrease in the ventilated cavity from the 150 mm (Roof 4.2A, Fig. 4.17) to a 100 mm (Roof 4.2B, Fig 4.18). Similar changes are observed when the cavity is removed altogether130.

130

Compare Roof 4.2C (Fig. 4.19) and Roof 4.2D (Fig. 4.20). _______________________________________________________________________________________________________________ Page: 77 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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Fig. 4.23:

300 mm solid concrete slab.

Fig. 4.24:

300 mm solid concrete slab with a exterior reflective finish.


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Fig. 4.25:

191 mm solid concrete slab with a exterior reflective finish.

Fig. 4.26:

82 mm solid concrete slab with an exterior reflective finish.


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4.4 SOLAR HEAT GAIN FACTOR (SHF): Roofs in hot-humid climates should have a limit of 4.5% SHF131. If we compare the SHF values for the different roofs (Table 4.5), the following may be observed: (a) All the roofs except Roof 4.1G, Roof 4.2E, Roof 4.2F, Roof 4.3 and Roof 4.3D, have satisfied the above SHF recommendation. As would be expected, all these roofs had a high exterior surface absorptivity. Roof 4.2E was a fibre-concrete roof tile without any ceiling, thus reducing the “U” Value and SHF. (b) The roof with the lowest SHF value was Roof 4.1A. This was a hollow-pot slab with exterior reflective finish, a ventilated cavity and an insulated lining (Table 4.0). (c) The roof with the highest SHF value was Roof 4.3D. This was a 82 mm solid concrete slab with a high exterior surface absorptivity (See Table 4.0). Table 4.1: Computed hourly solar radiation (SR) and energy flow through different roofs. Time: 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700

Energy flow through different roofs in Kilowatts/hour 4.1 4.1A 4.1B 0.12 0.1 0.16 0.11 9 E-2 0.15 0.11 9 E-2 0.15 0.12 9 E-2 0.15 0.11 0.1 0.16 0.1 8 E-2 0.14 0.11 9 E-2 0.15 0.1 8 E-2 0.14 7 E-2 6 E-2 0.11 1 E-2 0 5 E-2 -9 E-2 -0.1 -6 E-2 -0.15 -0.17 -0.13 -0.17 -0.18 -0.16 -0.17 -0.19 -0.17 -0.14 -0.15 -0.14 -8 E-2 -0.1 -9 E-2 -1 E-2 -3 E-2 -2 E-2

SR (KW/sq.m) 4.1C 0.17 0.15 0.15 0.15 0.15 0.13 0.14 0.13 0.1 3 E-2 -7 E-2 -0.14 -0.16 -0.17 -0.13 -7 E-2 0

0 0 0 0 0 0 0 0.165 0.42 0.65 0.83 0.95 0.995 0.95 0.83 0.65 0.42

131

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1800 1900 2000 2100 2200 2300 2400

4 E-2 9 E-2 0.14 0.15 0.15 0.14 0.12

2 E-2 7 E-2 0.11 0.13 0.12 0.11 0.1

3 E-2 9 E-2 0.14 0.17 0.17 0.16 0.15

6 E-2 0.12 0.17 0.2 0.19 0.18 0.17

0.165 0 0 0 0 0 0

Table 4.2: Computed hourly solar radiation (SR) and energy flow through different roofs. Time: 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Energy flow through different roofs in Kilowatts/hour 4.1D 4.1E 4.1F 0.17 0.21 0.22 0.15 0.18 0.2 0.15 0.18 0.19 0.15 0.17 0.18 0.14 0.17 0.18 0.12 0.14 0.15 0.12 0.15 0.15 0.11 0.13 0.14 9 E-2 0.1 0.11 2 E-2 4 E-2 4 E-2 -8 E-2 -6 E-2 -6 E-2 -0.15 -0.13 -0.13 -0.16 -0.14 -0.13 -0.16 -0.13 -0.12 -0.12 -8 E-2 -5 E-2 -5 E-2 0 3 E-2 3 E-2 9 E-2 0.13 9 E-2 0.16 0.2 0.15 0.22 0.26 0.2 0.27 0.31 0.22 0.29 0.31 0.21 0.27 0.29 0.19 0.25 0.27 0.17 0.22 0.23

SR (KW/sq.m) 4.1G 0.33 0.29 0.27 0.25 0.23 0.2 0.19 0.17 0.14 8 E-2 0 -4 E-2 -1 E-2 0.995 5 E-2 0.15 0.26 0.38 0.46 0.51 0.53 0.52 0.47 0.42 0.36

0 0 0 0 0 0 0 0.165 0.42 0.65 0.83 0.95 0.95 0.83 0.65 0.42 0.165 0 0 0 0 0 0


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Table 4.3: Computed hourly solar radiation (SR) and energy flow through different roofs. Time: 100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

4.2 0 0 0 0 0 0 0 0 4 E-2 0.1 0.16 0.21 0.26 0.28 0.28 0.25 0.21 0.15 7 E-2 2 E-2 1 E-2 0 0 0

Energy flow through different roofs in Kilowatts/hour 4.2A 4.2B 4.2C 4.2D 4.2E 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 2 E-2 2 E-2 4 E-2 7 E-2 0.16 4 E-2 6 E-2 9 E-2 0.18 0.43 7 E-2 9 E-2 0.15 0.28 0.67 0.1 0.13 0.2 0.37 0.86 0.12 0.16 0.24 0.43 0.99 0.13 0.18 0.26 0.45 1.05 0.14 0.18 0.26 0.44 1.01 0.13 0.16 0.23 0.39 0.88 0.11 0.14 0.19 0.31 0.7 8 E-2 5 E-2 0.13 0.21 0.46 4 E-2 5 E-2 7 E-2 9 E-2 0.19 2 E-2 2 E-2 2 E-2 1 E-2 1 E-2 1 E-2 1 E-2 1 E-2 1 E-2 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

SR (KW/sq.m) 4.2F 0 0 0 0 0 0 0 0 0.33 0.85 1.34 1.73 1.99 2.09 2.01 1.77 1.4 0.92 0.38 2 E-2 0 0 0 0

0 0 0 0 0 0 0 0.165 0.42 0.65 0.83 0.95 0.995 0.95 0.83 0.65 0.42 0.165 0 0 0 0 0 0

Table 4.4: Computed hourly solar radiation (SR) and energy flow through different roofs. Time: 100 200 300 400 500

Energy flow through different roofs in Kilowatts/hour 4.3 4.3A 4.3B 4.3C 4.3D 0.48 0.32 0.29 0.23 0.34 0.42 0.29 0.24 0.18 0.27 0.41 0.29 0.24 0.18 0.24 0.39 0.28 0.22 0.16 0.21 0.36 0.28 0.21 0.15 0.19

SR (KW/sq.m) 0 0 0 0 0


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600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

0.32 0.31 0.28 0.23 0.11 -7 E-2 -0.18 -0.19 -0.17 -5 E-2 0.1 0.27 0.4 0.52 0.62 0.64 0.61 0.56 0.51

0.24 0.25 0.23 0.18 6 E-2 -0.13 -0.25 -0.29 -0.3 -0.22 -0.1 4 E-2 0.15 0.27 0.36 0.4 0.39 0.37 0.33

0.17 0.17 0.15 0.11 0 -0.15 -0.23 -0.21 -0.16 -4 E-2 0.11 0.26 0.37 0.45 0.51 0.5 0.45 0.39 0.32

0.12 0.13 0.11 8 E-2 1 E-2 -9 E-2 -0.1 -3 E-2 6 E-2 0.21 0.36 0.48 0.55 0.57 0.57 0.5 0.42 0.34 0.27

0.14 0.15 0.12 0.1 7 E-2 4 E-2 0.12 0.29 0.48 0.7 0.9 1.04 1.08 1.05 0.96 0.81 0.66 0.52 0.41

0 0 0.165 0.42 0.65 0.83 0.95 0.995 0.95 0.83 0.65 0.42 0.165 0 0 0 0 0 0

Notes: a. “E” is an abbreviation of “Exponential”. b. Negative readings denote energy loss from the building. c. Positive readings denote energy gained by the building. Table 4.5: Time lag (TL) and solar heat gain factor (SHF) of different roofs. Roof number:

4.1 4.1A 4.1B 4.1C 4.1D 4.1E

Time of day with: Max. Max. Solar Heat Input Flow Hour Hour a. 2150 a. 2100 a. 2150 a. 2100 a. 2100 a. 2100

Time Lag (TL) Hours 8.5 8 8.5 8 8 8

Total Heat Flow KW/h 4.1 2 6.5 7.4 8.1 12.7

Total Solar On Roof KW/h b. b. b. b. b. b.

Solar Heat Gain Factor (SHF) % 0.68 0.33 1.08 1.23 1.34 2.10


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4.1F 4.1G 4.2 4.2A 4.2B 4.2C 4.2D 4.2E 4.2F 4.3 4.3A 4.3B 4.3C 4.3D

a. a. a. a. a. a. a. a. a. a. a. a. a. a.

2150 2000 1450 1500 1450 1450 1400 1400 1400 2100 2100 2000 1950 1800

8.5 7 1.5 2 1.5 1.5 1 1 1 8 8 7 6.5 5

14.7 29.5 10.4 5.2 6.7 9.6 16.3 37.1 74.3 31.7 15.7 20.9 26.8 53.5

b. b. b. b. b. b. b. b. b. b. b. b. b. b.

2.43 4.88 1.72 0.86 1.11 1.59 2.70 6.14 12.3 5.25 2.60 3.46 4.44 8.86

Notes: a. The time of day with the maximum solar input was 1300 hours. b. The total solar radiation on the roof for the five days that were simulated was 604 KW/h.

4.4.1 TIME-LAG: FRED was used to compute hourly solar radiation (SR) and energy flow through different roofs for a period of five days. The results were compiled into Tables (Tables 4.1 to 4.4) and the times with the peak solar radiation (SR) and the peak energy flow through the different roofs were noted. The difference between the two is the time-lag (Table 4.5). If we compare the five tables, the following may be observed: (a) The various modifications on the hollow-pot slab have a slight effect on the time that the peak energy flows through the roof (Table 4.1 and Table 4.2). The peak solar radiation is at 13.00 hour while the maximum energy flow is between 21.00 and 22.00 hours. The time-lag for Roof 4.1G to Roof 4.1 is approximately 7 to 8.5 hours (Table 4.5). (b) The fibre-concrete roof tile shows a quick response to an increase in the solar radiation. The pattern of energy flow through the roof closely resembles that of the solar radiation (Table 4.3). The time-lag for Roof 4.2F to 4.2, ranges between 1 to 2 hours (Table 4.5). Time-lag values especially are only important for thick materials with high density and specific heat.


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(c) There is a larger range of time-lag between solid concrete slabs of different thicknesses. It ranges between 5 to 8 hours for Roofs 4.3D to 4.3 respectively (Table 4.5). (d) Roof 4.2 to Roof 4.2F have satisfied the time-lag recommendation of less than 4 hours (Chapter 4). These were fibre concrete tile roofs with various modifications (See Table 4.0). (e) Thin materials are more responsive to changes in the external surface absorptivity, the insulation lining and the ventilation cavity. The time-lag decreases drastically by removing any of these in sequence. (f) Thick materials are unaffected by changes in the external surface absorptivity, the insulation lining and ventilated cavity. A 300 mm solid concrete slab (Roof 4.3) is unaffected by the increase in the external surface absorptivity.

4.4.2 CONCLUDING REMARKS: The internal environment of buildings is affected by the use of passive (natural systems) or active (mechanical) devices. A greater use of passive measures will reduce the dependence on active devices, with the effect of reducing the energy required for running such devices as airconditioning units. Passive methods require a deep understanding of the building fabric and how it responds to changes in climatic factors such as the wind, solar radiation and humidity levels. Enforced performance standards for each element of the building can ensure that comfort levels are maintained without the use of active devices. In the case of the roof, recommendations are given in the form of requirements for the solar heat gain factor (SHF), the time-lag and ceiling temperature restrictions. The ceiling temperature and the SHF are more important for thin roofs than the timelag. A time-lag of less than 4 hours can easily be achieved by the use of a ceiling with a low “U” Value. A thick roof is more complicated. It is important to restrict the SHF Value as this will affect the amount of heat transmitted through the roof and will be a determinant on the amount of energy used in cooling the building. Adequate time-lag can only be achieved by reducing the thickness of the roof and introducing a ventilated cavity. It is also important to reduce the ceiling temperatures below ambient. The hollow-pot slabs have high time-lag, but the SHF values were the lowest and the ceiling temperatures were acceptable. Thus, it will perform better than a solid concrete slab. In warm-humid climates, the materials should be made as thin as possible. A thin roof has a rapid response and it would be easier to adjust the overall performance by adding a reflective exterior finish, an insulation lining or a ventilated cavity. A thick roof will not respond to any of these _______________________________________________________________________________________________________________ Page: 85 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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measures. In the case of the hollow-pot slab, the insulation lining was not contributing effectively to the overall performance of the roof. This was due to the location of the insulation lining. An exterior insulation will give a better result compared to an interior one. The fibre concrete roofing tile (FCT) generally performed better compared to the hollow-pot slab or a solid concrete slab. But in special circumstances where the use of a concrete slab is inevitable, than a hollow-pot slab should be recommended. Though some more research is necessary to improve the time-lag in particular.

Fig. 4.27:

82 mm solid concrete slab without an exterior reflective finish.


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5.0 CHAPTER 5: ENERGY BALANCE: _______________________________________________________________________________ Any efficient system will ensure that the energy gone into making any building element can at least save an equivalent amount of energy. At the limiting situation, the capital energy should be paid back through savings in operating energy over a stipulated period of time, i.e. the energy balance. In practical terms, the building may be built in about two years, but it will function for many more years, depending on “how the world copes with running and servicing the relatively uneconomical buildings which are still being built”132. For this reason, the energy cost of running a building over its lifetime133 would be greater than the energy cost of its construction. For this reason, many workers in the past have considered the former to be unimportant. However, even in the U.K., the average energy cost of construction of a small house is more than three times its average annual energy consumption, and in a developing country, with lower consumption levels, that ratio might be even higher134. A comparison between the energy input and thermal roof performance is essential when making a decision on the type of roof construction. Indeed, it would be folly to choose a roof construction that was economical in building energy, but it had a large heat gain that there were excessive running costs. Likewise, it would be uneconomical to use a roof construction with a high energy input which doesn’t improve the overall thermal performance of the roof. Factors that have to be considered when deciding the balance between the energy used to make the roof and performance requirements, including the following:

5.1 COST AND PERFORMANCE135 OF DIFFERENT ROOFS: Locational and economical factors are strong indicators on the choice between mechanical devices (i.e. active) and building methods that are sympathetic to climatic factors (i.e. passive aids). An analysis of the energy consumption of different buildings can help to illustrate this point. Questionnaires (Appendix 5.1 and 5.2) were circulated to some architects and the actual users of a selected number of buildings in Kenya and the results were compiled into a table (Table 5.1). The electricity bill for a house in Mombasa (Kenya) varies between £2 to £10 per month136. Out of this, 132

Haseltine: 1975. In lighting, air-conditioning, etc. 134 Spence and Cook: 1983. 135 Sometimes referred to as “Cost/Benefit” Analysis. 136 Currency conversion of £1 to Kshs. 30/74 was used (July, 1988). _______________________________________________________________________________________________________________ Page: 87 of 145 133


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approximately 18% will be due to the use of fans or air-conditioning units. This is quite a large figure if you compare it to the monthly income group of approximately £160 that was used for the design of these houses. The use of mechanical aids shows that there must be a defect in the thermal performance of the building fabric with respect to the climatic adaptability. This house had a pitched 100 mm concrete roof slab with a concrete tile exterior and a plastered ceiling (Fig. 1.13). Such a roof will not satisfy the time-lag and solar heat gain factor (SHF) recommendations. The long time-lag of approximately 9 hours (Chapter 4) necessitates the use of a fan to supplement air movement and ventilation throughout the year. The house is currently using approximately 2 hours per day as night cooling. Building construction is relatively cheap in developing rather than developed countries. This makes it more economical to improve the thermal performance of the roof rather than installing an airconditioning unit or even a small fan. Calculations by the author using information from the “Architecture” Magazine137, showed that the cost of a galvanized iron sheets (GIS) roof including labour and materials for a 4 m by 4.5 m room, was £127 (Kshs. 3,904/-). A 0.2 KW fan costs about £160 (Kshs. 5,000/-) while a wall mounted air-conditioning unit costs about £1269 (Kshs. 39,000/). The thermal performance of the roof can be improved by using a ceiling made of a thin material with a low “U” Value and ventilating the roof cavity. A cypress T&G ceiling including labour and materials can be built at an extra cost of £85 (Kshs. 2,601/-). The total cost of the roof will be less than the cost of even a fan and the total energy consumption in the form of electricity will be reduced by at least 20% (See Table 5.1). Energy use is also affected by the standard of living of the people. It was the trend in office blocks built in the mid-twentieth century, to introduce artificial ventilation and lighting. These office buildings are associated with huge electricity bills compared to an office building with natural light and ventilation (Table 5.1). The monthly energy consumption due to the air-conditioning unit is approximately 100,000 KWh, which accounts for approximately 34% of the electricity bill. Air-conditioning (a/c) units are also expensive to maintain. The annual a/c maintenance cost for the air-conditioned office block was £48,796 (Table 5.1). The roof is only effective in high-rise office development when considering the top level. Better results will be achieved in the future, by considering the overall design of the building.

137

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Table 5.1: Preliminary results of the air-conditioning and overall electrical energy survey. Results from Questionnaires 1 and 2 (Appendix 5.1 and 5.2). Item (units)

Building name and type (location) Residential Mid twentieth House, Mombasa. Century a/c Office, Nairobi.

Floor area (sq.m). 16.2 Monthly electricity bill (£) a. 2.54 Monthly a/c or fan d. 0.52 Electricity bill (£). Monthly a/c maintenance (£) Average cost of 1KWh of c. 0.03 Electricity (£). Monthly average electricity 76.6 Energy consumption (KWh). Monthly average energy 15.6 Consumption for a/c equipment (KWh). Percentage of a/c energy 20.4 Consumption (%). Annual elec. & maint. Bill 1.88 Per sq.m (£/sq.m). Annual electrical a/c bill 0.4 Per sq.m (£/sq.m). Annual a/c energy cons. 11.6

32,000 7,878 e. 2,700

Late twentieth century office with Natural light and vent., Nairobi. 4,200 912 -

b. 4,066 0.03

0.03

291,772

33,735

100,000

-

34.3 4.48

2.61

1.01 37.5

-

Notes: a. The current exchange rate is 30.74 Kshs. For 1 pound sterling (£). b. An annual air-conditioning maintenance cost of £48,796 divided into 12 monthly installments. c. Residences are charged a higher rate of Kshs. 1.02 per KWh, while offices are charged Kshs. 0.83 per KWh. d. Night cooling or approximately 2 hours daily (except April and May when it increases to 4 hours). e. Permanent air-conditioning during the working period (approximately 7.5 hours per day). _______________________________________________________________________________________________________________ Page: 89 of 145 Building Science Text Book Series: Book 3: Topical Themes:

Yusuf H. Ebrahim


5.2 ENERGY RATING AND COMFORT LEVELS: The degree of comfort depends on the people’s expectations and lifestyle. It is common knowledge that the higher the income level of a people, the higher will be their expectations. Performance standards have to be adjusted accordingly, for a building can be designed to meet standards depending on what the people can afford, without causing a major health risk related to poorly designed buildings. As Koenigsberger and Lynn (1965), supported their standpoint on the ceiling temperatures restriction (See Chapter 2): “those who have to count their pennies should endeavor to keep the ceiling temperatures as close to 4 deg.C as possible”. An imposition of a very high thermal performance standard may aggravate the housing problem. Out of the existing 440,000 urban households in Kenya, only about 30% have sufficient incomes to afford minimum-cost conventional housing138. In Nairobi (Kenya), between a half and two-thirds of the households could not afford even a house139 of £300 to £1500. The failure of the so-called low-cost housing scheme to meet the needs of the poor has led one Indian expert to say, that “what the poor need is not low-cost housing, but no-cost housing”140. This can only be done by using locally available natural or intermediate materials. Changes have to be initiated by the government through the adoption of relevant policies. A rural house is only considered to be of a “permanent” condition, if the roof is made of at least corrugated iron sheets or better material141. On the contrary, Koenigsberger and Lynn (1965) suggest that a corrugated iron sheet roof should only be acceptable for temporary buildings, due to its poor thermal performance. The same applies to the asbestos cement sheets which are affected by algae growth due to the warm-humid climate. A thatch roof is considered to be a temporary material and a council building approval will not be granted. This need not be the case, as practical work in Zambia has shown that an improved method of binding the thatch and proper maintenance142 had increased the lifespan of the roof (Fig. 5.1). A “grade II” bye-law which will be used for buildings of a temporary or semi-permanent nature is currently being compiled in Kenya. Amendments will be necessary as the knowledge and thermal performance standards are improved. 138

Moi: 1984. The cheapest that can be built with modern materials such as cement and fired bricks. 140 Agarwal: 1982. 141 Moi: 1984. 142 Spence: 1978. _______________________________________________________________________________________________________________ Page: 90 of 145 139


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Legislative laws on the thermal performance of buildings have to be introduced. The building code143 of Kenya, don’t include a section on the climatic requirements of buildings. This may be one reason why buildings in different climatic zones within Kenya, may look exactly the same.

Fig. 5.1:

Thatch roof in Zambia, using an improved method of building the grass.

Fig. 5.2:

Labour-intensive appropriate materials (Villagers making sundried bricks in Kashgar, China).

143

A set of laws passed by parliament. _______________________________________________________________________________________________________________ Page: 91 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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Transportation is a major energy input and should be rationalized. Developing countries should heed Gandhi’s advice to Indians of using building materials which have all been found within a radius of five miles (8.1 km) from the building site144. Urban housing requires a higher thermal performance specification compared to rural or peri-urban housing. Experiments have shown that there is a great diversity within the micro-climate145 and especially within the urban area. This will affect the performance of buildings, though further research is needed in this direction. The avoidance of air-conditioning by design can offer huge savings of energy. But it is also important to note, that a building which was originally designed to be non air-conditioned, but failed to perform to the required thermal standards, and subsequently had to be air-conditioned, will probably cost more to run than one designed for air-conditioning at the outset146. This may be the case with lower cost housing where the designer anticipated that the occupants would be more tolerant to lower comfort standards. A rise in the standards of living may lead to an enormous increase in energy demand due to the use of cheap packaged air-conditioners in buildings of unsuitable design for air-conditioning.

5.3 ENERGY POLICY AND ECONOMIC DIRECTION: If we assume a given standard of development, a decrease in use of mechanical energy will lead to an increase in use of human energy (Fig. 5.2 and 5.3). Developing countries are faced with problems of unemployment and housing. Yet, they insist on using materials which have large manufacturing costs and huge energy inputs. A low energy high efficiency policy will create employment147 and the avail the materials necessary for housing. The use of locally produced building materials will ease the balance of payments problem that many developing countries are facing and it will also create an incentive for the development of indigenous industries.

144

Spence: 1980. The climate of a particular area. 146 Baker: 1987. 147 Most of the low energy materials require labour intensive processes. _______________________________________________________________________________________________________________ Page: 92 of 145 145


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Fig. 5.3:

Energy-intensive modern materials (steel works in U.K).

Fig. 5.4:

Fibre concrete roof sheets, Tanzania.


Yusuf H. Ebrahim


5.4 CONCLUDING REMARKS: There is no single solution to the choice of building materials which will satisfy all the design variables. The choice will depend on such factors as the climate of the area in question, the locally available materials and building skills and the people’s lifestyle and expectations. There are all the forces that shaped traditional societies. Modern building forms which are designed to meet very specific conditions without an adequate environmental adaptation, are prone to future problems. The amount of capital energy used to make and build a building element will depend on the energy used for manufacturing, transporting and constructing each of the composite materials. Capital energy can be saved in the following ways: (a) Using more energy efficient manufacturing techniques, (b) Switching from more to less energy intensive materials and techniques, (c) Recycling materials, (d) Using less material148. The amount of operating energy used is determined by the climate of the area and the thermal performance of the building. A building with a greater reliance on passive methods of ventilation and cooling the building will use less energy compared to a building using active149 devices. This study showed that it was cheaper to improve the thermal performance standards of a roof compared to installing even a small fan. The maintenance and the annual energy consumption costs were also favorable towards the passive designs. The fibre concrete roof tile (Fig. 5.4), performed better than both the hollow-pot and solid concrete slabs. It had a low capital energy input and satisfied the thermal performance standards for a warmhumid climate. A hollow-pot slab had a large capital energy input and required a better method of reducing the time-lag. A solid concrete slab should not be used in warm-humid regions due to the large time-lag in particular. To a certain extent, the energy intensity of different materials or techniques will be reflected in their financial coat, so that a cheap solution will tend to be an energy-efficient solution also150. In the long-run, the price of energy is liable to rise relative to the other factors of production such as human labour or soils and it will be in the best interest of a country to promote the use of techniques which make the most rational use of the local resources. 148

Spence and Cook: 1983. Air-conditioning. 150 Spence and Cook: 1983. _______________________________________________________________________________________________________________ Page: 94 of 145 149


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6.0 CONCLUSIONS: _______________________________________________________________________________ The problems that are currently being forced by the developing countries stem from their heavy reliance on fuels and technologies from the developed countries. Most of the machinery and the fuels to power these, which form the back-bone to the country’s development strategy, are imported from the developed countries. This makes the importing country vulnerable to changes in the economic and political policies of the supplier country. A sudden increase in the price of fuels can disrupt the development process and possibly even cause economic stagnation. The developed countries are trying to rectify problems pertaining to their “cheap-energy policy”. Before the energy crises, energy was so cheap that passive methods of heating and ventilating the buildings were not considered. Thus, many of the developed countries are now faced with large energy bills that could have avoided if a long-term planning was done. In many cases, these countries only have the option of trying to reduce the energy demand. The developing countries have other options open to them and they can avoid making the same mistakes as the developed countries. Change must take place in a gradual and calculated manner. The developing countries need to identify possible weaknesses in their development strategies and work towards a solution that will make the best possible use of the local resources without causing a fall in the standards of living of her citizens. This can only be done through research in specific areas of study, with the aim of eventually implementing the results. It will be slow process and in many cases, substantial amounts of resources will have to be diverted from the actual nation building, so as to sustain a long-term venture. The benefits of research generally out-weigh the costs. Large amounts of the country’s resources151 are currently being unemployed or underemployed due to the lack of relevant information or a proper coordinating procedure. This study showed that large amounts of fuels and materials were used to build different building elements, even though they were not necessary and in some cases, they worsened the thermal performance of the building. The country can save large amounts of energy and resources by just educating the people and demanding that the professionals and designers in particular, adhere to environmental laws. Existing performance standards for building materials have to be up-graded and especially, when related to the thermal performance and energy use. This should go further than a thermal resistance 151

Material, labour and capital. _______________________________________________________________________________________________________________ Page: 95 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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requirement, and should include standards related to the time-lag, solar heat gain factor and ceiling temperatures. More research is needed to establish comfort standards for different climatic regions and ways of achieving these. There is a need to appraise the existing knowledge on the basic environmental design concepts and especially those related to tropical countries. Coordination and cross-reference of existing information is imperative if duplication and misunderstanding is o be avoided. Calculation methods and applications related to such items as the time-lag have to be standardized and legislative laws drawn-up in the necessary countries. This will ensure that designers build buildings that will be suitable for the different climatic regions, so as to reduce the gross national energy demand. It is important to gradually build-up the information on various building materials, and how they respond to different climates. This can only be done by splitting the problem into its essentials and making studies of the individual variables. In terms of thermal design, this involves the use of theoretical heat flow calculations which have limitations which as Koenigsberger and Lynn (1965) say: “Stem from the necessity of having to generalize and simplify processes that are infact extremely complex and subject to a great variety of conditions”. The shortfalls of theoretical work will have to be tested through practical experimentation in the field and in the laboratory. But the advantage is that, It gives “direction to practical research and development and makes it possible for us to dispense with guesswork and base our designing on an understanding of the processes that occur in nature” (Koenigsberger and Lynn: 1965). Development opens the eyes and horizon of the people to new life-styles and technologies. Designers and researchers will have to be equipped and ready to tackle these new conditions. Environmental design concepts have to be applied to the different building elements and building types, so as to adapt them to the tropical climate and the social fabric. Most of the new or intermediate materials will be heterogeneous in nature. This will involve research on the individual materials, together with the different combinations and permutations that are possible, so as to identify the advantages and disadvantages of each choice. Change has to start at the lower end of the bottle-neck. A gradual reduction of high-energy materials is necessary, for these have been the cause of the rapid destruction of the architectural heritage, combined with a total indifference to the local cultural traditions, building materials and _______________________________________________________________________________________________________________ Page: 96 of 145 Building Science Text Book Series: Book 3: Topical Themes:

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environmental conditions. As the former President of Tanzania, Mr. Julius Nyerere (H.E.) said in 1977, “the widespread addiction to cement and tin roofs is a kind of mental paralysis”152. Cement or “European Soil”, as he called it, has become a matter of prestige. Research should be geared to reinstate the elevated position that the traditional materials had at one time commanded. As Denyer (1978) says: “one only has to consider for a moment the vocabulary used to refer to them153 to realize that even for those who know and respect other aspects of African Culture, it is hard to avoid being drawn into a web f selective and distorted perception”. In many cases, the material may fail to perform to the desired standards due to the wrong usage, related to the weakness rather than the strength of the material. In essence, “Earth is no magic solution to the housing problem of developing countries. There is no such thing. In theory, any material- even paper- is suitable for building, if you know how to use it, you design well with it, and maintain it properly” (Armstrong: 1988). Finally, it is important to “cut the coat to fit the cloth”. The resources in most of the developing countries are scarce, while the housing problem is worsening. A system of priorities has to be studied and worked out, on the many and varied component parts of a house. As Laurie Baker, an architect for the Indian Poor has said: “There are plenty of nice things one would like to have in one’s house but, if there is a limited amount of money available for building, one must be prepared to pick out the essential from the long, expensive list of “nice” things. It is possible and most desirable to go through the many component parts of a building one by one and decide whether you really need them” (Spence: 1980).

152

Agarwal: 1982. Including such basic words as “mud” and “hut”, which in English have such derogatory overtones. _______________________________________________________________________________________________________________ Page: 97 of 145 153


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7.0 REFERENCES: _______________________________________________________________________________ Agarwal, A. (1982). Let them live in mud. New Scientist, 16th December, pp. 741 – 747. Allwood, B.O. et al. (1975). Steel designer’s manual. Prepared for the Constructional Steel Research and Development Organization. Crosby Lockwood Staples, London, 4th edition, pp. 1034 – 1041. Armstrong, S. (1988). Pied a Terre. New Scientist, 10th March, pp. 60 -64. Baker, N. (1985). The use of passive solar gains for the pre-heating of ventilation air. Chapter A6: Outline documentation of FRED AIR. ECD Partnership, London, U.K. Dr. N.V. Baker now at the Martin Centre, University of Cambridge. Blair, T. (1980). Problem cities: Cairo and Nairobi. Architectural Association Quarterly, vol. 12, no. 1, pp. 22 – 23. BS 8110. The structural use of concrete. Clauses 3.12.5.3 and 3.12.11.2.9. Bullard, A.W. (1987). A worldwide compendium of information on selected low-cost building materials, 1987: fibre concrete roofing. September. Burberry, P. (1981). Impact of materials upon energy use. The architecture of energy by D. Hawkes and J. Owers (ed.), The Martin Centre of Architecture and Urban Studies, University of Cambridge, Dept. of Architecture. Constructional Press, pp. 64 – 71. Cain, A. et al. (1976). Indigenous building and the third world. Ekistics 242 (January), pp. 29 – 32. Chapman, P. (1975). Fuel’s paradise, energy options for Britain. Penguin Books Ltd., Harmondsworth, Middlesex, England, pp. 40 – 57. Chapman, P. and Roberts, F. (1983). Metal resources and energy. Butterworths Monographs on materials. Butterworths, London, pp. 9 – 220.


Yusuf H. Ebrahim


Clarke, J.A. (1979). ESP users’ manual appendix. Architecture and Building Aids Computer Unit Strathclyde (ABACUS), Department of Architecture, University of Strathclyde, 131 Rottenrow, Glasgow G4 0NG. pp. 4 – 5. Correa, M.C. (1976). Third world housing: space as a resource. Ekistics 242 (January), pp. 33 – 38. De Blij, H.J. (1968). Mombasa, an African city. African Studies Centre, Michigan State University. Northwestern University Press. Denyer, S. (1978). African traditional architecture. The impact of modernization. Heinemann, Nairobi, pp. 191 – 193. Denyer, S. (1988). African traditional architecture: recipe for survival. Lecture at the RIBA, 66 Portland Place, London W1N 4AD (22nd March). Ebrahim, Y. (1987). Thermal roof design for tropical provided housing. Essay one, M’Phil (one year) course in architecture (environmental design option), University of Cambridge, Department of Architecture (December), pp. 1 – 14. Ebrahim, Y. (1988). Transfer of technology in vernacular architecture. Essay four, M’Phil (one year) course in architecture (environmental design option), University of Cambridge, Department of Architecture (April), pp. 1 – 25. Evans, B. (1986). Understanding natural fibre concrete: its application as a building material. Intermediate Technology Publications Ltd., pp. 1 – 8. Evans, M. (1980). Housing, climate and comfort. The Architectural Press, London. Gartner, E.M. and Smith, M.A. (1976). Energy costs of house construction. Building Research Establishment, U.K., current paper CP47/76, pp. 144 – 155. Givoni, B. (1969). Man, climate and architecture. Elsevier Architectural Science Series, Elsevier Publishing Company Ltd., London, pp. 106, 115, 131 and 148. Gram, H. et al. (1984). Natural fibre concrete. Report from a SAREC-financed research and development project, SAREC report R2: 1984 (Swedish Agency for Research Co-operation with Developing Countries, S-105 25 Stockholm), pp. 8 – 98. _______________________________________________________________________________________________________________ Page: 99 of 145 Building Science Text Book Series: Book 3: Topical Themes:

Yusuf H. Ebrahim


Gribbin, J. (1982). The other face of development. New Scientist, 25th November, pp. 489 – 495. Gupta, V. (1987). Thermal efficiency of building clusters: an index for non air-conditioned buildings in hot climates. Energy and urban form by D. Hawkes et al. (ed.), Butterworth, London, pp. 133 – 145. Harris-bass, J. (1981). Cooler homes for hot climates. Middle East Construction Paper, U.K. Building Research Establishment, September, pp. 86. Haseltine, B.A. (1975). Comparison of energy requirements for building materials and structures. The Structural Engineer (September), no. 9, vol. 53, pp. 357 – 365. Hooper, C. (1975). Design for climate, guidelines for the design of low cost houses for the climates of Kenya. Housing Research and Development Unit (HRDU), University of Nairobi, P.O. Box 30197, Nairobi. Kenya Building Centre, Nairobi (January), pp. 31 – 48. Koenigsberger, O. and Lynn, R. (1965). Roofs in the warm humid tropics. Architectural Association paper, no. 1. Koenigsberger, O. et al. (1978). Manual of tropical housing and building; part one: climatic design. Longman, London, pp. 70. Lewcock, R. (1980). The need for special studies of the problems of third world architecture. Architectural Association Quarterly, vol. 12, no. 1, pp. 28 – 29. Mackillop, A. (1972). Low energy housing. The Ecologist (December), pp. 4 – 10. Markus, T.A. and Morris, E.N. (1980). Buildings, climate and energy. Pitman Publishing Ltd., London, pp. 310 – 343. Martin, P. et al. (1971). IHVE Guide, book a 1970. The Institute of Heating and Ventilation Engineers, London, pp. A6 – 23. Mathu, K. (1987). Imaginative use of local materials vital: How to make housing cheap? Architecture, The official journal of The Architectural Association of Kenya, vol. 9, no. 9 (September/October), pp. 25 – 26.


Yusuf H. Ebrahim


Meyeroff, B. (1987). Robert’s House, Lake Baringo (Kenya). Architecture in development, MIMAR 26 (December), pp. 52 – 59. Moi, D.A. (Hon.) (1984). Development Plan (1984 – 1988). 5th Development Plan, introduction by the president. Government Printer, Nairobi, pp. 33 – 473. Mpolokoso, E. (1980). Zambia; the need for a national training and research centre for human settlements development. Architectural Association Quarterly, vol. 12, no. 1, pp. 22 – 23. Mwangi, S. et al. (1986). Alternative construction technologies. A presentation paper by S. Mwangi (ITDG project engineer), M. Waliaula (HRDU research fellow) and Dr. M. Fisher (AA-K Technical Support Unit). O’Keefe, P. et al. (ed.) (1984). Energy and development in Kenya: opportunities and constraints. Energy, Environment and Development in Africa 1. The Beijer Institute, The Royal Swedish Academy of Sciences (Stockholm) and The Scandinavian Institute of African Studies (Uppsala), Sweden, pp. 37 and 151 – 152. Petherbridge, P. (1974). Limiting the temperature in naturally ventilated buildings in warm climates. Building Research Establishment, Current Paper 7/74 (February), pp. 1 – 22. Spence, R. (1978). Rural housing in Zambia. Report of a study for the Zambia Council for Social Development and Sponsored by The British Council (December). Spence, R. (1980). Laurie Baker: architect for the Indian poor. Architectural Association Quarterly, vol. 12, no. 1, pp. 30 – 39. Spence, R. (1980a). Small-scale production of cementitious materials. Intermediate Technology Publications Ltd., London, pp. 8 – 18. Spence, R (1987). Soil-cement blocks: selection of soils and cement content. The Martin Centre for Architectural and Urban Studies, University of Cambridge. Building Technical File (October), no. 19, pp. 47 – 51. Spence, R. and Cook, D. (1983). Building materials in developing countries. John Wiley and Sons, Chichester, pp. 301 – 304.


Yusuf H. Ebrahim


Strauss, H. (1980). Passive cooling where it’s hot and humid; or what people did to stay cool before air-conditioning and what you can do once you can’t afford it. Alternative sources of energy, n. 44 (July/August), pp. 24 – 27. Szokolay, S.V. (1981). Cooling problems and responses in predominantly overheated humid regions. International passive and hybrid cooling conference, Miami Beach (Florida), proceedings p. 651 – 659 (November). S.V. Szokolay, Architectural Science Unit, University of Queensland, St. Lucia Q. 4067 Australia. UNIDO (1976). UNIDO for industrialization (United Nations Industrial Development Organization): building materials and constructional industries. OP 209.57.06(76). United Nations (1986). 1983/84 Statistical yearbook. Thirty-fourth issue, Department of International Economic and Social Affairs, Statistical Office, New York, pp. 850 – 866. W’O Okot-uma, R. (1987). Project framework: local raw materials for housing construction. Project officer, Commonwealth Science Council (CSC), London.


Yusuf H. Ebrahim


8.0 APPENDIX: _______________________________________________________________________________

8.1 APPENDIX 1.0: CONVERSION TABLE: Multiplication factor: Prefix: 1 000 000 000 10E9 Giga 1 000 000 10E6 Mega 1 000 10E3 Kilo

Symbol: G M K

Quantity:

Unit:

Symbol:

Energy, heat:

Joule

J

Power, heat: Flow rate:

Watt Newtons metres Per second Joules per second

W (1W=1J/s) Nm/s

Imperial unit x conversion: Factor = SI value. 1 Btu = 1055.06 J 1 KWh = 3.60 MJ 1 Btu/h = 0.293 W 1 hp = 746 W

J/s

1 ft/1 bf = 1.356 J

Thermal Conductivity (k):

Watts per metre degree Celsius.

W/m deg.C

1 Btu in/sq.ft h deg.F = 0.144 W/m deg.C

Thermal Transmittance (v):

Watts per square degree Celsius.

W/sq.m deg.C

1 Btu/sq.ft h deg.F = 5.678 W/sq.m deg.C

Temperature:

Degree Celsius

deg.C

1 deg.F = 9/5 deg.C + 32.


Yusuf H. Ebrahim


8.2 APPENDIX 3.0: Calculation of the energy consumption of a fibre concrete tile (F.C.T). Item:

Cement: Sand: Fibre: Water: Machinery: Total:

Content per Sq.m covered: (kg) 6 18 0.018 3.3

Content per kg. 0.22 0.66 0.001 0.12

Energy consumption: MJ/kg b. 6 b. 0.3 b. 0.01 a. 0.003

Total: MJ 1.32 0.2 0.001 0.003 1.524

Symbol/source: Bullard: 1987. a. author (by calculation). b. see table 3.1.

8.3 APPENDIX 3.1: Calculation of the energy consumption of a soil cement block (S.C.B). Item:

Cement: Soil: Total:

Percentage of Item % a. 4 a. 96

Content per kg. 0.04 0.96

Energy consumption: MJ/kg b. 6 b. 0

Total: MJ 0.24 0 0.24

Symbol/source: Author (by calculation). a. Spence: 1987. b. see table 3.1.


Yusuf H. Ebrahim


8.4 APPENDIX 4.0: Calculation of the “U” Value for a hollow-pot slab with external finishes and a ventilated cavity. Item:

Resistivity: m.degC/W

External surface: 30 mm paving slabs: 2.63 20 mm screed: 2.44 3 mm bitumen felts: 2 30 mm screed: 2.44 90 mm concrete web: 0.71 25 mm clay skin: 1.19 50 mm cavity: 50 mm insulation polystyrene: 33.3 25 mm clay skin: 1.19 12 mm plaster: 6.25 Internal surface: Total resistance:

Conductivity: W/m.degC. 0.38 0.41 0.50 0.41 1.40 0.84 0.03 0.84 0.16

Resistance: sq.m degC/W 0.032 0.08 0.05 0.006 0.05 0.06 0.03 a. 0.176 1.67 0.03 0.075 a. 0.105 2.364

Conductance: W/sq.m degC a. 31 12.5 20 166.7 20 16.7 33.3 a. 5.67 0.6 33.3 13.3 a. 9.48 b. 0.423

Symbol/source: Clarke: 1979. a. Koenigsberger et al: 1978. b. Conductance = 1/resistance.


Yusuf H. Ebrahim


8.5 APPENDIX 4.1: Capacitances of different nodes: ROOF 4.1: Hollow pot slab with paving slabs external finish, bitumen felts on screeds, insulation and ventilated cavity. Node number:

a. first material + Second material Thickness d. Specific d. Density Heat

1

2

3

4

5

6

7

8

m m 0.02

J/kg.degC J/kg.degC 837

kg/cu.m kg/cu.m 2100

a. Total area

c. Total capacitance

J/sq.m.degC J/sq.m.degC

sq.m

Wh/degC

26366

17.2

126

0.02 837 0.01 840

2100 26366 1200 10080

36446

17.2

174.1

0.01 840 0.002 1000

1200 10080 1700 2550

12630

17.2

60.3

0.002 1000 0.02 840

1700 2550 1200 15120

17670

17.2

84.4

0.02 840 0.02 653

1200 15120 2100 31540

46660

17.2

222.9

0.02 653 0.02 653

2100 31540 2100 31540

63080

17.2

301.4

0.02 653 0.02 837

2100 31540 1900 20674

52214

17.2

249.5

0.01 837 -

1900 -

20674

17.2

98.8


Yusuf H. Ebrahim


9

10

11

12

0.03 1380

25

862.5

17.2

1.12

0.03 1380 0.01 837

25 862.5 1900 20674

21537

17.2

102.9

0.01 837 0.01 1000

1900 20674 600 3600

24274

17.2

116

0.01 1000 -

600 -

3600

17.2

17.2

13

e. 52.88

Notes: Appendix 4.1 to 4.7. a. Capacitance = area ( + ). b. Solar fraction = solar radiation x area x absorptivity. c. To convert from J/deg.C to Wh/deg.C, the total has to be divided by 3600 (1W = J/s, see conversion tables). d. Clarke: 1979. e. The capacitance for the room node = ( + 200%)/3600 = ( + . 200/100)/3600 = 52.88 Wh/deg.C. f. Ambient conductance = surface conductance x surface area. The ambient conductance for node 1 = 31.3 x 17.2 = 537.5. g. Koenigsberger et al: 1978. h. Average daily air temperature = 27.8 deg.C (see table 1.3).


Yusuf H. Ebrahim


i. Heat required to raise temperature by 1 deg.C (1 hour) = (ventilation rate x volume of room = 52.88, specific heat for air = 1200 J/sq.m, temperature difference = 1). j. Internodel conductance (G) = surface area x conductivity/thickness. The internodel conductance is always calculated from the internal node moving outward and excluding nodes that have already been accounted. k. Solar fraction of a surface = surface area x absorptivity. l. This has been increased to account for the ventilation rate. m. Author (by calculation). n. The conductance for a ventilated cavity is 4.0 (W/sq.m deg.C), while for an unventilated cavity it is 0.567 W/sq.m deg.C (Koenigsberger et al: 1978). o. Koenigsberger et al: 1978. p. Clarke: 1979. q. Mwangi: 1986. f. Surface conductance.


Yusuf H. Ebrahim


8.6 APPENDIX 4.2: Capacitances of different nodes: ROOF 4.2: Fibre concrete tiles with a fibre insulation ceiling and ventilated cavity. Node number:

1

2-10

11

12

13

a. first material + Second material Thickness d. Specific Heat m J/kg.degC m J/kg.degC 0.003 m. 1000 -

-

a. Total area


sq.m

Wh/degC

d. Density kg/cu.m kg/cu.m m. 1818


5455 17.2

-

26.1

0

0.01 1000

300

1800 17.2

8.6

0.01 1000 -

300 -

1800 17.2

8.6

-

-

-

e. 52.88


Yusuf H. Ebrahim


8.7 APPENDIX 4.3: Capacitances of different nodes: ROOF 4.3: Solid concrete slab. Node number: a. first material + Second material Thickness d. Specific Heat m J/kg.degC m J/kg.degC 1 0.01 653 2-11

12

a. Total area


sq.m

Wh/degC

d. Density kg/cu.m kg/cu.m 2100


0.01 653 0.01 653

2100 2100

19198 19198

0.01 653 -

2100 -

19198

19198 17.2

92

38396 17.2

184

17.2

13

92 e. 52.88

8.8 APPENDIX 4.4: Internodel conductance (Roof 4.1). (see note “j”). Node: 1-2 2-3 3-4 4-5 5-6 6-7 7-8 8-9 9-10 10-11

Area: 17.2 “ “ “ “ “ “ “ “ “

Conductivity: 0.38 0.41 0.50 0.41 1.4 “ 0.84 n. 0.4 0.03 0.84

Thickness: 0.03 0.02 0.003 0.03 0.045 “ 0.025 0.05 0.025

Source: o. o. o. o. o. o. o. p. o. o.

Conductance: 218 353 2867 235 535 535 578 69 10 578


Yusuf H. Ebrahim


11-12 12-13

“ “

0.16 r. 9.5

0.012

o. o.

229 164

Thickness: 0.01

Source: q. o. p. o.

Conductance: 6364 208 86 164

Source: p. o.

Conductance: 892 164

8.9 APPENDIX 4.5: Internodel conductance (Roof 4.2). (see note “j”). Node: Area: 1-2 17.2 2-3 to 10-11 “ 11-12 “ 12-13 “

Conductivity: 2.22 n. 12.1 0.06 r. 9.5

0.012

8.10 APPENDIX 4.6: Internodel conductance (Roof 4.3). (see note “j”). Node: Area: 1-2 to 11-12 17.2 12-13 17.2

Conductivity: 1.4 r. 9.5

Thickness: 0.027

8.11 APPENDIX 4.7: Solar fraction for different roofs. (see note “k”). Roof:

Area:

absorptivity:

4.1 4.2 4.3

17.2 17.2 17.2

0.65 0.60 0.65

solar fraction: (node 1) 11.18 10.32 11.18


Yusuf H. Ebrahim


8.12 APPENDIX 4.8: Calculation of the sol-air temperatures for the peak external air temperature and the peak incident solar radiation (Roof 4.3A). a). sol-air temperature (Teo) for the peak external air temperature: Maximum external air temperature: (14.00 hours). Solar irradiance at 14.00 hours: Surface resistance: Long-wave radiation: Surface of the roof: Absorptivity (exposed concrete) Emissivity by L.W.R. Teo

= = = =

Tao + Rso (A.Igv – E.Ie) 31.7 + 0.045 ((0.65 x 950) – (0.9 x 100)) 31.7 + 23.7 55.4 deg.C

(Tao) =

31.7 deg.C

(Igv) = (Rso) = (Ie) =

950 W/sq.m 0.045 deg.C sq.m/W 100 W/sq.m

(A) (E)

0.65 0.9

= =

(a) (a)

(Markus and Morris: 1980).

b). sol-air temperature (Teo) for the peak incident solar radiation. Maximum solar irradiance: (13.00 hours). External air temperature: (13.00 hours).

(Igv) =

995 W/sq.m

(Tao) =

31.6 deg.C

Teo

(Markus and Morris: 1980).

= = = =

Tao + Rso (A.Igv – E.Ie) 31.6 + 0.045 ((0.65 x 995) – (0.9 x 100)) 31.6 + 25.1 56.7 deg.C.

Source/symbol: Markus and Morris: 1980 a. Petherbridge: 1974. b. Clarke: 1979. _______________________________________________________________________________________________________________ Page: 112 of 145 Building Science Text Book Series: Book 3: Topical Themes:

Yusuf H. Ebrahim


8.13 APPENDIX 4.9: Computed hourly nodal temperatures for Roof 4.1 (see Table 4.0 and Fig. 4.8). Time:

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Conc. Void Surface: Node: Node: 27.6 31.5 33.8 27.5 31.1 33.4 27.1 30.6 32.9 26.8 30.2 32.4 26.4 29.8 32 26.3 29.5 31.6 26 29.1 31.2 25.8 28.8 30.7 28.2 29 30.4 32.9 30.1 30.2 38.4 31.9 30.3 43.2 34 30.6 46.7 36.1 31.2 48.9 38 32.1 48.9 39.3 33 47.3 39.9 34 44.1 39.7 34.8 39.8 38.9 35.5 34.7 37.4 35.8 30.6 35.6 35.9 29.3 34.3 35.7 28.6 33.3 35.3 28.2 32.6 34.9 28 32 34.4

Ceiling Node: 27.7 27.5 27.2 26.9 26.6 26.4 26.1 25.9 25.8 26.2 27.1 28.1 29 29.9 30.4 30.7 30.6 30.4 30 29.4 28.9 28.6 28.2 28

Int. Ambient: 27 26.8 26.5 26.2 25.9 25.8 25.4 25.3 25.4 26.1 27.6 29.1 30.1 31 31.3 31.2 30.7 30.2 29.5 28.6 28 27.7 27.4 27.3

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim


8.14 APPENDIX 4.10: Computed hourly nodal temperatures for Roof 4.1A (see Table 4.0 and Fig. 4.9). Time:

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Conc. Void Surface: Node: Node: 27.3 29.6 31 27.1 29.3 30.8 26.8 29.1 30.5 26.5 28.8 30.2 26.2 28.5 29.9 26.1 28.2 29.6 25.7 28 29.3 25.6 27.7 29.1 26.8 27.8 28.8 29.5 28.3 28.7 33 29.4 28.7 36 30.7 28.8 38.3 32 29.2 39.8 33.2 29.7 40 34 30.3 39.1 34.4 30.9 37.3 34.4 31.4 34.9 34 31.8 32 33.2 32.1 29.5 32.2 32.2 28.6 31.4 32.1 28.1 30.8 31.9 27.8 30.3 31.6 27.6 30 31.4

Ceiling Node: 27.5 27.3 27 26.7 26.4 26.2 25.9 25.7 25.7 26 27 28 28.9 29.8 30.3 30.5 30.5 30.2 29.8 29.2 28.7 28.3 28 27.8

Int. Ambient: 26.9 26.8 26.4 26.1 25.8 25.7 25.4 25.2 25.3 26.1 27.6 29 30 30.9 31.2 31.1 30.7 30.1 29.4 28.5 27.9 27.6 27.3 27.2

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim


8.15 APPENDIX 4.11: Computed hourly nodal temperatures for Roof 4.1B (see Table 4.0 and Fig. 4.10). Time:

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Conc. Void Surface: Node: Node: 27.2 29.3 30.2 27 29 29.9 26.7 28.7 29.6 26.4 28.4 29.3 26.1 28.1 29 26 27.8 28.7 25.7 27.5 28.4 25.5 27.3 28.1 26.7 27.3 27.9 29.4 27.9 27.8 32.9 28.9 27.8 36 30.2 28.1 38.2 31.6 28.5 39.7 32.8 29.1 39.9 33.6 29.7 39 34.1 30.3 37.2 34.1 30.9 34.8 33.7 31.3 31.9 32.8 31.5 29.5 31.9 31.5 28.5 31.1 31.3 28 30.4 31.1 27.7 30 30.8 27.5 29.6 30.5

Ceiling Node: 28 27.8 27.5 27.2 26.9 26.8 26.5 26.3 26.2 26.5 27.4 28.3 29.1 29.9 30.4 30.6 30.5 30.4 30 29.5 29.1 28.8 28.5 28.3

Int. Ambient: 27.1 26.9 26.6 26.3 26 25.9 25.6 25.4 25.5 26.2 27.7 29.1 30.1 31 31.3 31.2 30.7 30.2 29.5 28.6 28.1 27.7 27.5 27.4

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim


8.16 APPENDIX 4.12: Computed hourly nodal temperatures for Roof 4.1C (see Table 4.0 and Fig. 4.11). Time:

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Conc. Void Surface: Node: Node: 27.4 28.5 30.2 27.2 28.2 29.8 26.9 27.9 29.4 26.6 27.5 29 26.2 27.2 28.7 26.1 27 28.3 25.8 26.7 28 25.6 26.4 27.7 26.5 26.7 27.4 28.8 27.9 27.3 31.9 29.8 27.5 34.9 32 28 37.3 33.8 28.7 38.9 35.4 29.6 39.4 36.3 30.5 38.9 36.5 31.3 37.4 35.9 31.9 35.3 34.8 32.3 32.7 33.3 32.5 30.3 31.6 32.3 29 30.5 32 28.4 29.8 31.6 28 29.3 31.1 27.7 28.9 30.7

Ceiling Node: 28.1 27.9 27.5 27.2 26.9 26.7 26.4 26.1 26.1 26.4 27.2 28.2 29.1 30 30.5 30.8 30.8 30.6 30.3 29.8 29.3 29 28.7 28.4

Int. Ambient: 27.1 27 26.6 26.3 26 25.9 25.5 25.4 25.5 26.2 27.7 29.1 30.1 31 31.3 31.2 30.8 30.3 29.5 28.7 28.1 27.8 27.6 27.4

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim


8.17 APPENDIX 4.13: Computed hourly nodal temperatures for Roof 4.1D (see Table 4.0 and Fig. 4.12). Time:

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Conc. Void Surface: Node: Node: 27.6 27.7 30.1 27.4 27.5 29.6 27 27.1 29.2 26.7 26.8 28.7 26.3 26.5 28.3 26.2 26.3 27.9 25.8 25.9 27.6 25.6 25.7 27.2 26.4 26.4 27 28.5 28.3 27 31.4 31.1 27.3 34.3 33.8 28.1 36.6 36.1 29 38.3 37.9 30.1 39 38.6 31.3 38.7 38.4 32.2 37.4 37.3 32.9 35.5 35.5 33.3 33.1 33.2 33.3 30.8 31 33 29.5 29.7 32.4 28.7 28.9 31.8 28.3 28.4 31.2 27.9 28.1 30.6

Ceiling Node: 28.1 27.9 27.5 27.2 26.8 26.6 26.3 26 25.9 26.3 27.2 28.2 29.1 30 30.6 30.9 31 30.9 30.5 30 29.5 29.1 28.8 28.5

Int. Ambient: 27.1 27 26.6 26.3 25.9 25.9 25.5 25.3 25.4 26.2 27.6 29.1 30.1 31 31.3 31.3 30.8 30.3 29.6 28.8 28.2 27.8 27.6 27.4

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim


8.18 APPENDIX 4.14: Computed hourly nodal temperatures for Roof 4.1E (see Table 4.0 and Fig. 4.13). Time:

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Conc. Ceiling Surface: Node: Node: 27.5 27.6 28.5 27.3 27.4 28.2 26.9 27 27.8 26.6 26.7 27.4 26.3 26.4 27 26.1 26.2 26.8 25.8 25.9 26.5 25.6 25.7 26.2 26.4 26.4 26.1 28.4 28.3 26.4 31.3 31 27.3 34.2 33.8 28.3 36.6 36.1 29.3 38.3 37.8 30.3 38.9 38.5 31 38.6 38.3 31.4 37.3 37.2 31.6 35.4 35.4 31.5 33 33.1 31.2 30.7 30.9 30.7 29.4 29.6 30.1 28.6 28.8 29.7 28.2 28.3 29.3 27.9 28 28.9

Int. Ambient: 27.2 27 26.7 26.3 26 25.9 25.6 25.4 25.5 26.2 27.7 29.1 30.1 31.1 31.4 31.4 31 30.5 29.8 29 28.4 28 27.7 27.6

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim


8.19 APPENDIX 4.15: Computed hourly nodal temperatures for Roof 4.1F (see Table 4.0 and Fig. 4.14). Time:

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Conc. Ceiling Surface: Node: Node: 27.5 27.6 28.6 27.2 27.4 28.3 26.9 27 27.9 26.6 26.7 27.5 26.2 26.3 27.1 26.1 26.2 26.9 25.8 25.9 26.5 25.6 25.6 26.3 26.4 26.3 26.2 28.4 28.3 26.5 31.3 31 27.3 34.2 33.8 28.4 36.5 36.1 29.4 38.3 37.8 30.4 38.9 38.5 31.2 38.6 38.3 31.7 37.3 37.1 31.9 35.4 35.3 31.8 32.9 33 31.5 30.6 30.8 31 29.3 29.5 30.4 28.6 28.8 29.9 28.1 28.3 29.4 27.8 27.9 29

Int. Ambient: 27.3 27.1 26.7 26.4 26 25.9 25.6 25.4 25.5 26.2 27.7 29.1 30.2 31.1 31.5 31.5 31.1 30.6 29.9 29.1 28.5 28.1 27.8 27.6

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim


8.20 APPENDIX 4.16: Computed hourly nodal temperatures for Roof 4.1G (see Table 4.0 and Fig. 4.15). Time:

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Conc. Ceiling Surface: Node: Node: 27.9 28 29.6 27.6 27.7 29.1 27.2 27.3 28.6 26.8 26.9 28.1 26.4 26.6 27.6 26.2 26.3 27.3 25.9 26 26.9 25.7 25.8 26.6 27.3 27.2 26.5 30.9 30.6 26.8 35.6 35.1 27.9 40.2 39.5 29.1 43.8 43 30.5 46.4 45.6 31.8 47.2 46.5 32.9 46.4 45.9 33.7 44.1 43.8 34.1 40.7 40.6 34.1 36.3 36.5 33.7 32.4 32.7 33 30.4 30.7 32.2 29.4 29.6 31.5 28.7 28.9 30.8 28.3 28.5 30.2

Int. Ambient: 27.6 27.3 26.9 26.6 26.2 26.1 25.7 25.5 25.6 26.3 27.9 29.4 30.5 31.6 32 32.1 31.8 31.4 30.6 29.7 29.1 28.6 28.2 28

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim



100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Void 2 Void 1 Surface: Node: Node: 26.6 26.6 26.6 26.5 26.5 26.5 26.1 26.1 26.2 25.8 25.8 25.8 25.5 25.5 25.5 25.5 25.5 25.5 25.1 25.1 25.2 25 25 25 28.1 27.6 26.7 33.7 32.5 30 39.9 37.9 34.1 44.9 42.4 37.5 48.2 45.4 39.8 50 47.1 41.2 49.4 46.6 41 46.9 44.5 39.7 43 41.1 37.3 38 36.8 34.4 32.4 32 31.1 28.3 28.3 28.4 27.5 27.6 27.6 27.2 27.2 27.2 27 27 27 26.9 26.9 26.9

Ceiling Node: 26.6 26.5 26.2 25.8 25.5 25.5 25.2 25 25.5 26.8 29.1 31.1 32.5 33.5 33.7 33.2 32.2 31.1 29.7 28.3 27.6 27.2 27 26.9

Int. Ambient: 26.6 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.2 29.8 30.9 31.8 32 31.7 30.9 30.2 29.2 28.2 27.5 27.2 27 26.9

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim



100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Void 2 Void 1 Surface: Node: Node: 26.6 26.6 26.6 26.5 26.5 26.5 26.1 26.1 26.2 25.8 25.8 25.8 25.5 25.5 25.5 25.5 25.5 25.5 25.1 25.1 25.2 25 25 25 26.7 26.4 25.9 29.9 29.3 28 33.9 32.9 30.9 37.3 36 33.5 39.4 38 35.2 40.8 39.3 36.3 40.5 39.1 36.4 39.2 38 35.5 36.9 35.9 34.1 34 33.4 32.2 30.8 30.6 30.1 28.2 28.3 28.3 27.5 27.6 27.6 27.2 27.2 27.2 27 27 27 26.9 26.9 26.9

Ceiling Node: 26.6 26.5 26.2 25.8 25.5 25.5 25.2 25 25.3 26.5 28.5 30.3 31.5 32.5 32.7 32.3 31.5 30.6 29.4 28.3 27.6 27.2 27 26.9

Int. Ambient: 26.6 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.8 31.7 31.8 31.5 30.8 30.1 29.2 28.2 27.5 27.2 27 26.9

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim



100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Void 2 Void 1 Surface: Node: Node: 26.6 26.6 26.6 26.5 26.5 26.5 26.1 26.1 26.1 25.8 25.8 25.8 25.5 25.5 25.5 25.5 25.5 25.5 25.1 25.1 25.1 25 25 25 26.6 26.6 26.2 29.9 29.9 28.7 33.9 33.9 31.9 37.2 37.2 34.7 39.3 39.3 36.6 40.7 40.7 37.8 40.5 40.4 37.7 39.1 39.1 36.7 36.8 36.8 35 34 34 32.8 30.8 30.8 30.4 28.2 28.2 28.3 27.5 27.5 27.6 27.2 27.2 27.2 27 27 27 26.9 26.9 26.9

Ceiling Node: 26.6 26.5 26.2 25.8 25.5 25.5 25.2 25 25.4 26.6 28.7 30.6 31.8 32.8 33 32.6 31.7 30.7 29.5 28.3 27.6 27.2 27 26.9

Int. Ambient: 26.6 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.8 31.7 31.9 31.6 30.9 30.1 29.2 28.2 27.5 27.2 27 26.9

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim



100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Void 1 Ceiling Surface: Node: Node: 26.6 26.6 26.6 26.5 26.5 26.5 26.1 26.1 26.1 25.8 25.8 25.8 25.5 25.5 25.5 25.5 25.5 25.5 25.1 25.1 25.1 25 25 25 26.6 26.6 25.4 29.8 29.8 26.8 33.8 33.8 29 37.1 37 31 39.2 39.2 32.3 40.5 40.5 33.4 40.3 40.3 33.5 39 39 33.1 36.7 36.7 32.1 34 33.9 31 30.8 30.8 29.6 28.2 28.2 28.3 27.5 27.5 27.6 27.2 27.2 27.2 27 27 27 26.9 26.9 26.9

Int. Ambient: 26.6 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.8 30.9 31.8 31.9 31.6 30.9 30.2 29.2 28.2 27.5 27.2 27 26.9

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim



100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Ceiling Int. Surface: Node: Ambient: 26.6 26.6 26.6 26.5 26.5 26.5 26.1 26.1 26.1 25.8 25.8 25.8 25.5 25.5 25.5 25.5 25.5 25.5 25.1 25.1 25.1 25 25 25 26.5 25.7 25.3 29.7 27.4 26.3 33.5 30 28.3 36.7 32.2 30 38.8 33.7 31 40.2 34.7 32 40 34.8 32.1 38.7 34.2 31.8 36.5 32.9 31 33.8 31.5 30.2 30.7 29.8 29.2 28.3 28.3 28.2 27.5 27.6 27.5 27.2 27.2 27.2 27 27 27 26.9 26.9 26.9

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim


8.26 APPENDIX 4.22: Computed hourly nodal temperatures for Roof 4.2E (see Table 4.0 and Fig. 4.21). Time:

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Ceiling Int. Surface: Node: Ambient: 26.6 26.6 26.6 26.5 26.5 26.5 26.1 26.1 26.1 25.8 25.8 25.8 25.5 25.5 25.5 25.5 25.5 25.5 25.1 25.1 25.1 25 25 25 26.4 26.3 25.3 29.2 29.1 26.5 32.8 32.7 28.6 35.8 35.7 30.4 37.8 37.6 31.6 39.1 38.9 32.5 38.9 38.8 32.6 37.8 37.7 32.3 35.8 35.7 31.4 33.4 33.3 30.5 30.5 30.5 29.3 28.3 28.3 28.2 27.5 27.6 27.5 27.2 27.2 27.2 27 27 27 26.9 26.9 26.9

Ext. Ambient: 26.5 26.1 25.8 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim


8.27 APPENDIX 4.23: Computed hourly nodal temperatures for Roof 4.2F (see Table 4.0 and Fig. 4.22). Time:

100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Ceiling Int. Surface: Node: Ambient: 26.6 26.6 26.6 26.5 26.5 26.5 26.1 26.1 26.1 25.8 25.8 25.8 25.5 25.5 25.5 25.5 25.5 25.5 25.1 25.1 25.1 25 25 25 27.6 27.5 25.5 32.3 32.1 26.9 37.6 37.4 29.3 42.1 41.8 31.2 45 44.6 32.5 46.6 46.3 33.5 46.2 45.9 33.6 44.2 43.9 33.1 40.8 40.6 32.1 36.7 36.5 30.9 31.9 31.9 29.5 28.3 28.3 28.2 27.6 27.6 27.5 27.2 27.2 27.2 27 27 27 26.9 26.9 26.9

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim



100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Conc. Conc. Surface: Node 2: Node 1: 28 30.2 31.1 27.7 29.6 30.5 27.3 29.1 30 26.9 28.6 29.4 26.6 28.2 28.9 26.4 27.8 28.5 26 27.4 28 25.8 27 27.7 27.7 27.3 27.4 31.7 28.4 27.4 36.4 30.4 27.9 40.7 32.8 28.9 44 35.2 30.1 46.2 37.4 31.5 46.7 38.9 32.9 45.6 39.7 34.1 43.1 39.7 34.9 39.6 38.8 35.3 35.3 37.2 35.3 31.7 35.3 34.8 30.2 33.7 34.1 29.4 32.5 33.3 28.9 31.5 32.5 28.5 30.8 31.8

Ceiling Node: 30 29.5 29 28.5 28.1 27.7 27.3 27 26.8 26.9 27.5 28.4 29.3 30.4 31.3 32.1 32.6 32.9 32.8 32.5 32 31.5 31 30.5

Int. Ambient: 27.1 26.9 26.5 26.2 25.9 25.8 25.4 25.3 25.4 26.3 27.9 29.5 30.5 31.4 31.6 31.5 31 30.4 29.6 28.7 28.1 27.8 27.5 27.4

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim



100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Conc. Conc. Surface: Node 2: Node 1: 27.6 29 29.7 27.4 28.6 29.3 27 28.3 28.9 26.7 27.9 28.5 26.3 27.5 28.1 26.2 27.2 27.8 25.9 26.9 27.4 25.7 26.6 27.1 26.6 26.7 26.9 28.9 27.3 26.9 31.8 28.4 27.2 34.5 29.9 27.8 36.7 31.4 28.6 38.2 32.8 29.5 38.6 33.9 30.5 38.1 34.5 31.3 36.7 34.5 31.9 34.7 34.1 32.2 32.3 33.3 32.2 30.2 32.2 32 29.2 31.3 31.6 28.6 30.5 31.1 28.2 29.9 30.6 27.9 29.4 30.1

Ceiling Node: 28.9 28.6 28.2 27.8 27.5 27.2 26.9 26.6 26.4 26.6 27.1 27.9 28.6 29.5 30.2 30.7 31 31.1 31 30.7 30.3 30 29.6 29.2

Int. Ambient: 26.9 26.8 26.4 26.1 25.8 25.7 25.4 25.2 25.4 26.2 27.9 29.4 30.4 31.3 31.5 31.3 30.8 30.2 29.4 28.5 27.9 27.6 27.4 27.2

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim



100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Conc. Ceiling Surface: Node 1: Node: 28.1 29 28.7 27.7 28.5 28.2 27.3 28.1 27.8 26.9 27.6 27.4 26.6 27.2 27 26.3 26.9 26.7 26 26.6 26.3 25.8 26.3 26.1 26.2 26.2 25.9 27.6 26.5 26.2 29.7 27.4 27 32.1 28.7 28 34.3 30.2 29.2 36.1 31.8 30.4 37.2 33.1 31.4 37.5 34.1 32.2 36.9 34.5 32.5 35.7 34.5 32.6 33.9 33.9 32.3 32 33 31.7 30.7 32 31 29.8 31.1 30.4 29.1 30.3 29.7 28.5 29.6 29.2

Int. Ambient: 26.9 26.7 26.3 26 25.7 25.7 25.3 25.1 25.3 26.2 27.9 29.4 30.5 31.4 31.7 31.5 31 30.4 29.6 28.6 28 27.6 27.4 27.2

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim



100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Ceiling Int. Surface: Node: Ambient: 28.3 28.2 26.8 27.9 27.8 26.7 27.4 27.4 26.3 27 27 26 26.6 26.6 25.7 26.4 26.3 25.6 26.1 26 25.2 25.8 25.8 25.1 26.1 25.7 25.3 27.1 26.2 26.2 28.9 27.4 27.9 31.1 28.9 29.5 33.2 30.5 30.6 35 32 31.6 36.3 33.2 31.9 36.9 33.9 31.7 36.7 34.1 31.2 35.9 33.9 30.5 34.4 33.2 29.7 32.8 32.1 28.7 31.4 31.1 28 30.4 30.2 27.6 29.5 29.4 27.3 28.9 28.8 27.2

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim



100 200 300 400 500 600 700 800 900 1000 1100 1200 1300 1400 1500 1600 1700 1800 1900 2000 2100 2200 2300 2400

Nodal temperatures (deg.C): Ext. Ceiling Int. Surface: Node: Ambient: 29.1 29 26.9 28.5 28.4 26.8 27.9 27.8 26.3 27.4 27.3 26 26.9 26.8 25.7 26.6 26.5 25.6 26.2 26.1 25.3 25.9 25.9 25.1 26.6 25.9 25.3 28.5 26.7 26.2 31.5 28.3 28 34.9 30.5 29.7 38.2 32.7 30.9 41.1 34.9 32 43 36.6 32.3 43.7 37.7 32.3 43.2 38 31.7 41.6 37.6 31.1 39 36.5 30.1 36.1 34.9 29.1 33.9 33.3 28.3 32.2 31.9 27.8 30.9 30.7 27.5 29.9 29.8 27.3

Ext. Ambient: 26.5 26.1 25.8 25.5 25.5 25.1 25 25.2 26.2 28.1 29.7 30.7 31.6 31.7 31.4 30.7 30 29.1 28.1 27.5 27.2 27 26.9 26.6


Yusuf H. Ebrahim


8.33 APPENDIX 5.1: QUESTIONAIRE 1: Name of household:…………………………………………………………………………………... Location:……………………………………………………………………………………………… Q1.

Q2. Q3. Q4.

Do you have a fan or air-conditioning unit in your house? (yes/no)………………………………………………………………………………………… (state which one you have or both)……………………………………………………………. How many fans or air-conditioning units do you have per house? …………………………………………………………………………………………………. In which room do you use the fan or air-conditioning unit? (is it located in the living room, bedroom, dining room, etc)…………………………………. How many hours per day do you use the fan or air-conditioning unit? (answer this question in the following way)

Month:

Hours per day:

January: February: March: April: May: June: July: August: September: October: November: December:

. . . . . . . . . . . .

Q5. Q6.

Q7.

Which room is The fan used: . . . . . . . . . . . .

Who uses the fan (is it you or any member of the family: . . . . . . . . . . . .

What type of fan do you have? (for example, National, Phillips, Hitachi, etc)…………………………………………………. What is the power of the fan or air-conditioning nit in watts, kilowatts or watts per hour? (look up in the manual of the fan or it is usually written at the bottom of the fan. For example, power: 3W)………………………………………………………………………….. How much do you pay for electricity per month to the city council and how many units of electricity do you use?.................................................................................................................


Yusuf H. Ebrahim


Q8.

What is the price of one unit of electricity?................................................................................

8.34 APPENDIX 5.2: QUESTIONAIRE 2: Q1.

What is the cost of a standard small fan or air-conditioning unit (usually mounted on the wall) for a house in Mombasa? (Please send me a leaflet of a fan and the air-conditioning unit). Kshs……………………………………………………………………………………...

Q2.

What is the power consumption of such a unit? (in watts, kilowatts or watts per hour)………………………………………………………….

Q3.

What is the annual energy consumption of a hose in Mombasa due to this air-conditioning unit or fan?..................................................................................................................................

Q4.

What is the price of a unit of electricity in Kenya? (you can find out from your electricity bill)……………………………………………………

Q5.

What is the monthly electricity bill for a house in Nairobi? (it is a personal question, but I will treat it with confidentiality).

Q6.

What is the annual air-conditioning energy requirement for an office building? (You could find out from the management of the office or the service engineer)…………………………

Q7.

What is the energy requirement of any other office building? (so that I can compare it with Q6)……………………………………………………………


Yusuf H. Ebrahim



CHAPTER 3:

PRODUCT PRICE GUIDE:


Yusuf H. Ebrahim


1.0

PRODUCT PRICE GUIDE:

DATED: January 2008: The following is the recommended price guide for various products: Retail Price Guide: Building Science Text Book Series: Product EE: Within Kenya Name: Code: Kshs. Building Science Text Book Series: Book 1: Elementary Course: E1000 9966-784-48-9 Book 1: Part A: Framed Elementary Course: E1010 1,990/9966-784-07-1 Book 1: Part 1: Introduction to Climatology and Meteorology: E1100 1,990/ISBN:

Abroad: US $ 35 35

Book 1: Part 2: Elementary Thermal Design, Ventilation and Solar Control: E1200 9966-784-00-4 Book 1: Part 2: Section 1: Elementary Thermal Design: E1210 1,990/35 9966-784-01-2 Book 1: Part 2: Section 2: Elementary Solar Control: E1220 1,990/35 9966-784-02-0 Book 1: Part 2: Section 3: Elementary Ventilation and Air Flow Design: E1230 1,990/- 35 9966-784-03-9 Book 1: Part 2: Section 4: Elementary Artificial, Hybrid and Intelligent Climatic Systems: E1240 1,990/35 Book 1: Part 3: Elementary Lighting Design: E1300 9966-784-04-7 Book 1: Part 3: Section 1: Natural Lighting Design: E1310 1,990/35 9966-784-05-5 Book 1: Part 3: Section 2: Artificial Lighting Design: E1320 1,990/35 9966-784-06-3 Book 1: Part 3: Section 3: Elementary Artificial, Hybrid and Intelligent Lighting Systems: E1330 1,990/35 Book 1: Part 4: Elementary Acoustics Design and Noise Control: E1400 9966-784-08-X Book 1: Part 4: Section 1: Noise Control: E1410 1,990/35 9966-784-09-8 Book 1: Part 4: Section 2: Room Acoustics: E1420 1,990/35 9966-784-10-1 Book 1: Part 4: Section 3: Elementary Artificial, Hybrid and Intelligent Acoustic Systems: E1430 1,990/35 9966-784-11-X Book 1: Part 5: Elementary Sustainable Design: E1500 1,990/35 Book 1: Part 6: Elementary Past Examination Papers: 2008: Book 1: Part 6: Section 1: Year 1: 2008: 9966-784-55-1Book 1: Part 6: Section 2: Year 2: 2008: 9966-784-54-3Book 1: Part 6: Section 3: Year 3: 2008: Book 1: Part 6: Section 4: Year 4: 2008: Book 1: Part 6: Section 5: Year 5: 2008:

E1600 E1610 E1620 E1630 E1640 E1650

1,990/1,990/1,990/1,990/1,990/-

35 35 35 35 35

9966-784-53-5Book 1: Part 7: Elementary Thesis Index: 2008:

E1700 1,990/-

35

Book 1: Part 8: Elementary Sustainable Architecture Studio: 2008: E1800 Book 1: Part 8: Section 1: Elementary Studio 1: 2008: E1810 Book 1: Part 8: Section 2: Elementary Studio 2: 2008: E1820 Book 1: Part 8: Section 3: Elementary Studio 3: 2008: E1830 Book 1: Part 8: Section 4: Elementary Studio 4: 2008: E1840 Book 1: Part 8: Section 5: Elementary Studio 5: 2008: E1850 Book 1: Part 8: Section 6: Elementary Studio 6: 2008: E1860

1,990/1,990/1,990/1,990/1,990/1,990/-

35 35 35 35 35 35


Yusuf H. Ebrahim

Part 1: Appropriate Roofing & Energy Considerations for Warm-Humid Climates: _____________________________________________________________________________________________ Building Science Text Book Series: Book 2: Advanced Course: E2000 9966-784-49-7 Book 1: Part A: Framed Advanced Course: E2010 1,990/35 9966-784-12-8 Book 2: Part 1: The Human Factor in Environmental Design: E2100 1,990/35 9966-784-13-6 Book 2: Part 2: Applied Design Studio in Environmental Building Science: E2200 1,990/- 35 Book 2: Part 3: Advanced Thermal Design, Ventilation and Solar Control: E2300 1,990/- 35 9966-784-14-4 Book 2: Part 3: Section 1: Advanced Thermal Design: E2310 1,990/35 “Influence of Heat Island on the Comfort of the Building Users: Case of City of Nairobi”. 9966-784-15-2 Book 2: Part 4: Advanced Lighting Design: E2400 1,990/35 9966-784-16-0 Book 2: Part 5: Advanced Acoustics Design and Noise Control: E2500 1,990/35 9966-784-17-9 Book 2: Part 6: History of Regional Environmental Design: E2600 1,990/35 9966-784-18-7 Book 2: Part 7: Environmental Building Economics: E2700 1,990/35 9966-784-45-4Book 2: Part 8: Advanced Past Examination Papers: 2008: E2800 1,990/35 9966-784-46-2Book 2: Part 9: Advanced Thesis Index: 2008: E2900 1,990/35 Book 2: Part 10: Advanced Sustainable Architecture Studio: 2008: Book 2: Part 10: Section 1: Advanced Studio 1: 2008: Book 2: Part 10: Section 2: Advanced Studio 2: 2008: Book 2: Part 10: Section 3: Advanced Studio 3: 2008:

E21000 E21010 1,990/E21020 1,990/E21030 1,990/-

35 35 35

Building Science Text Book Series: Book 3: Topical Themes: E3000 9966-784-19-5 Book 3: Part 1: Appropriate Roofing and Energy Considerations for Warm-Humid Climates: E3100 1,990/35 9966-784-20-9 Book 3: Part 2: Daylighting Performance of Building Elements: E3200 1,990/35 (With Specific Application to Museums under Tropical Conditions). 9966-784-21-7 Book 3: Part 3: The Power of Deceit: A Dilemma of an Architect. E3300 (An Autobiography of Yusuf Ebrahim). 9966-784-22-5 Book 3: Part 4: Patenting software in Kenya: Problems and Myths Demystified. E3400 Book 3: Part 5: Pictures Talk: Virtually Recreating Dr. James Orloff. E3500 Book 3: Part 6: Pictures Talk: Virtually Recreating Mr. Atma Singh Hazara Singh. E3600 Book 3: Part 7: The Changing Face of Mrs. Lilian Lela Orloff Ebrahim. E3700 Book 3: Part 8: The Changing Face of Mr. Ebrahim Atma Singh Hazara Singh. E3800 Book 3: Part 9: The Greats in Environmental Design: From Geiger to Muneer.

E3900

Book 3: Part 10: S.V. Szokolay Memoirs: 9966-784-33-0 Book 3: Part 10: Section 1: 1965 Works: 9966-784-35-7 Book 3: Part 10: Section 2: Current Works:

E3110 E3111 1,990/E3112 1,990/-

35 35

Book 3: Part 11: E.F. Meffert’s Environmental Design Code: 9966-784-37-3 Book 3: Part 11: Section 1: Thermal Design: 9966-784-51-9 Book 3: Part 11: Section 2: Lighting Design: 9966-784-52-7 Book 3: Part 11: Section 3: Acoustic Design:

E3120 E3121 1,990/E3122 1,990/E3123 1,990/-

35 35 35


Yusuf H. Ebrahim

Part 1: Appropriate Roofing & Energy Considerations for Warm-Humid Climates: _____________________________________________________________________________________________ 9966-784-56-X Book 3: Part 11: Section 4: Tropical Design: E3124 1,990/35 Building Science Text Book Series: Book 4: Short Papers: E4000 9966-784-23-3 Book 4: Part 1: Essays in Environmental Design: E4100 1,990/35 Essay 1: Thermal Roof Design for Tropical Provided Housing: E4110 Essay 2: Environmental Considerations Shaping the Hospital Building and Governing its Space: E4120 Essay 3: Low Energy House in Cool Climates: E4130 Essay 4: Transfer of Technology in Vernacular Architecture: E4140 Essay 5: Low Energy Strategy in Speculative Atrium Office Buildings: E4150 9966-784-47-0Book 4: Part 2: Essays in Environmental Design: 6-10: E4200 1,990/35 Essay 6: Sustainable Materials and Construction Technology: E4210 Essay 7: Use of Environmental Laboratory in the Built Environment: E4220 Essay 8: Sensual Architecture: Revitalizing your Survival Instincts: E4230 Essay 9: Developing of Appropriate Intermediary Software for a Developing Tropical Country: “Ebenergy 2007”: E4240 Essay 10: Urban Environmental Degradation: Assessment using Analogue and Digital Techniques: E4250 Building Science Text Book Series: Book 6: Investigative & Exploratory Studies: E6000 Book 6: Part 1: Digital & Analogue Presentation Techniques: E6100 9966-784-34-9 Book 6: Part 2: e-Learning Methods: E6200 Book 6: Part 3: Universities Channel: E6300 9966-784-36-5 Book 6: Part 4: Early Warning, Monitoring & Mitigating Techniques for Sustainable Development: E6400 Book 6: Part 5: Experimental Research Methods: E6500 9966-784-38-1 Book 6: Part 6: Laboratory & On-site Techniques in Environmental Studies: E6600 9966-784-39-X Book 6: Part 7: Model Studies: Analogue & Digital Techniques: E6700 9966-784-40-3 Book 6: Part 8: Genesis of Nairobi: E6800 9966-784-41-1 Book 6: Part 9: Material Culture Project: E6900 9966-784-42-X Book 6: Part 10: Relationship between Propagation of AIDS and Comfort Criteria: E61000 9966-784-43-8 Book 6: Part 11: Setting up of an Institute of Environmental Studies as a Constituent Institute of a University: E61100 9966-784-44-6 Book 6: Part 12: Use of Environmental Laboratory Equipment & Apparatus: E61200 Building Science Text Book Series: Book 7: Marketing for Other Authors: E7000 Book 7: Part 1: Prof. Erich F. Meffert: E7100 1980: Hygrothermal Comfort in Lamu Town: A Building-density Settlement in the Warm-humid Climate of the Kenyan Coast. University of Nairobi, Department of Architecture, Environmental Science – Paper No.6. E7110 Book 7: Part 2: Rukwaro, Robert & Maina, Sylvester J.M.

E7200


Yusuf H. Ebrahim

Part 1: Appropriate Roofing & Energy Considerations for Warm-Humid Climates: _____________________________________________________________________________________________ 2006: Transformation of Maasai Art and Architecture. Applied Research Training Services (ARTS), Nairobi. E7210 Book 7: Part 3: Kenya Literature Bureau Publications: 2005: Secondary Physics: Students Book Four. Kenya Literature Bureau, Nairobi. Third Edition.

E7300 E7310

Ghaidan, Usam (1992): Lamu: A Study of the Swahili Town. Kenya Literature Bureau, Nairobi. Third Edition.

E7310

Building Science Text Book Series: Book 8: Joint Authorship with Others: E8000 Book 8: Part 1: Jointly with Dr. Robert Rukwaro: E8100 2007: History of Environmental Design in Kenya Communities: E8110 2007: Climate Culture Encyclopedia: E8120 Building Science Text Book Series: Book 9: Conference and Seminar Papers: E9000 Book 9: Part 1: Sustainable Materials and Construction Technology. AAK Mombasa Chapter: Seminar at Royal Court Hotel, Mombasa: 16th November 2006. E9100 1,990/35 Book 9: Part 2: Culture, Environmental and Sustainability Issues in the City of Nairobi. 3rd Year Seminar Series: Department of Architecture & Building Science, ADD Space 108, E9200 1,990/35 University of Nairobi: 30th November 2006. Book 9: Part 3: End-user Sensitization Workshop: Ebenergy Pro 2007 Special: Ebenergy Enterprises. Final Year Students, Undergraduate Course, Dept. Of Arch & BSc, UON: 14th February 2007. E9300 1,990/35 Book 9: Part 4: Sensual Architecture: Reviving & Revitalizing your Survival Instincts. 2nd Year Studio Lectures Series: 20th March 2007. E9400 1,990/35 Book 9: Part 5: Use of Environmental Laboratory in the Built Environment. Department of Architecture & Building Science (2nd Year) in collaboration with Department of Real Estate & Construction Management (1st Year), University of Nairobi: ADD Space 108: 4th April 2007. Guest Speakers: Yusuf Ebrahim & Njambi Kinyungu. E9500 1,990/35 Book 9: Part 6: Development of Appropriate Intermediary Software for a Developing Tropical Country: “Ebenergy 2007”. Conference Paper, Atlanta Conference on Science, Technology and Innovation Policy 2007: “Challenges and Opportunities for Innovation in the Changing Global Economy”. Presenter: Yusuf Ebrahim, Lecturer, University of Nairobi, Kenya. Venue: The Global Learning Center, Georgia Institute of Technology, Atlanta Georgia, USA. Date: Friday 19 October 2007. Time: 5 – 6.30 PM. E9600 1,990/35 Building Science Text Book Series: Book 10: Ongoing Work at Institute of Environmental Studies: E10000 9966-784-50-0 Book 10: Part 1: Recyclable Architecture: E10100 Book 10: Part 2: Environmental Documentaries: E10200 _______________________________________________________________________________________________________________ Page: 139 of 145 Building Science Text Book Series: Book 3: Topical Themes:

Yusuf H. Ebrahim

Part 1: Appropriate Roofing & Energy Considerations for Warm-Humid Climates: _____________________________________________________________________________________________ Book 10: Part 3: Cinema Production: E10300 Book 10: Part 4: Publishing & Micro-printing Techniques: E10400 Book 10: Part 5: Digital Library Services: E10500 Book 10: Part 6: Climate Watch: E10600 Book 10: Part 7: Reprinting Classical Environmental Books: E10700 Building Science Text Book Series: Book 11: Building Typologies: E11000 9966-784-57-8 Book 11: Part 1: Residential Architecture: E11100 9966-784-58-6 Book 11: Part 2: Housing Architecture: E11200 9966-784-59-4 Book 11: Part 3: Coastal (Warm-humid Climate) Architecture: E11300 9966-784-60-8 Book 11: Part 4: Touristic Accommodation & Ecological Architecture: E11400 9966-784-61-6 Book 11: Part 5: Medical Architecture: E11500 9966-784-62-4 Book 11: Part 6: Religious Architecture: E11600 9966-784-63-2 Book 11: Part 7: Commercial Architecture: E11700 9966-784-64-0 Book 11: Part 8: Planning Architecture: E11800 9966-784-65-9 Book 11: Part 9: Interior Architecture: E11900 9966-784-66-7 Book 11: Part 10: Educational Architecture: E111000 9966-784-67-5 Book 11: Part 11: Competitions in Architecture: E111100 9966-784-68-3 Book 11: Part 12: International Organizations Architecture: E111200 9966-784-69-1 Book 11: Part 13: Banks Architecture: E111300 9966-784-70-5 Book 11: Part 14: Sustainable Development and Environmental Design: E111400 9966-784-71-3 Book 11: Part 15: Bioclimatic Architecture: E111500 9966-784-72-1 Book 11: Part 16: Regional Typologies Architecture: E111600 9966-784-73-X Book 11: Part 17: Research Institutions Architecture: E111700 9966-784-74-8 Book 11: Part 18: Appropriate Technology Architecture: E111800 9966-784-75-6 Book 11: Part 19: Industrial Architecture: E111900 9966-784-76-4 Book 11: Part 20: Office Architecture: E112000 Building Science Text Book Series: Book 12: Architectural & Environmental Design Consultants Office Practice Notes: E12000 9966-784-77-2 Book 12: Part 1: Office Manual: E12100 9966-784-78-0 Book 12: Part 2: Typical Contracts and Documents: E12200 9966-784-79-9 Book 12: Part 3: Curriculum Vitae and Company Profiles: E12300 9966-784-80-2 Book 12: Part 4: Competitions: Competitor & Juror Compendium: E12400 9966-784-81-0 Book 12: Part 5: Contract Administration: E12500 9966-784-82-9 Book 12: Part 6: Design & Development: E12500 9966-784-83-7 Book 12: Part 7: Typical Details: E12700 9966-784-84-5 Book 12: Part 8: Drawing Standards: E12800 9966-784-85-3 Book 12: Part 9: Technical Drawings: E12900 9966-784-86-1 Book 12: Part 10: Presentation Techniques: E121000 9966-784-87-X Book 12: Part 11: Marketing Techniques E121100 9966-784-88-8 Book 12: Part 12: Continuous Professional Development (CPD): E121200 9966-784-89-6 Book 12: Part 13: Associated Offices and Companies: E121300 9966-784-90-X Book 12: Part 14: Consortiums: E121400 9966-784-91-8 Book 12: Part 15: Project Management and Construction: E121500 _______________________________________________________________________________________________________________ Page: 140 of 145 Building Science Text Book Series: Book 3: Topical Themes:

Yusuf H. Ebrahim

Part 1: Appropriate Roofing & Energy Considerations for Warm-Humid Climates: _____________________________________________________________________________________________ 9966-784-92-6 Book 12: Part 16: Environmental Design Consultancy: E121600 9966-784-93-4 Book 12: Part 17: Interior Architects and Product Designers: E121700 9966-784-94-2 Book 12: Part 18: Landscape Architecture: E121800 9966-784-95-0 Book 12: Part 19: Urban Planners and Architects: E121900 9966-784-96-9 Book 12: Part 20: Environmental and Architectural Journalism: E122000 Building Science Text Book Series: Book 13: Office Practice Documents & Software: E13000 9966-784-97-7 Book 13: Part 1: Ebbank © Software: Financial Management Package: E13100 9966-784-98-5 Book 13: Part 2: Ebfees © Software: Invoicing & Receipts Management Package: E13200 9966-784-99-3 Book 13: Part 3: Ebbq © Software: Mini-BQ, Valuations, Certification & Payment Advices: E13300 Book 13: Part 4: Ebpvouchers © Software: Payment Management Package: E13400 Building Science Text Book Series: Book 14: Dictionaries, Reference and Common Names: E14000 Book 14: Part 1: Dictionary and Reference Book: 2008: E14100 1,990/- 35 Building Science Text Book Series: Book 15: Fact Folders: Book 15: Part 1: Who’s Who: 2008: Book 15: Part 2: What’s What: 2008: Book 15: Part 3: How’s How: 2008: Book 15: Part 4: When’s When: 2008:

E15000 E15100 E15200 E15300 E15400

1,990/1,990/1,990/1,990/-

35 35 35 35

Building Science Text Book Series: Book 5: Software & Manuals: E5000 9966-784-24-1 Book 5: Part 1: Ebenergy© Software: E5100 9966-784-25-X Book 5: Part 2: Ebacoustics© Software: E5200 9966-784-26-8 Book 5: Part 3: Eblighting© Software: E5300 9966-784-27-6 Book 5: Part 4: Ebtemp© Software: E5400 9966-784-28-4 Book 5: Part 5: Ebvent© Software: E5500 9966-784-29-2 Book 5: Part 6: Ebeia© Software: E5600 9966-784-30-6 Book 5: Part 7: Ebeim© Software: E5600 9966-784-31-4 Book 5: Part 8: Ebsustain© Software: E5800 9966-784-32-2 Book 5: Part 9: Ebclimo© Software: E5900 Product EE: Within Kenya ISBN: Name: Code: Kshs. Building Science Text Book Series: Book 5: Software & Manuals: E5000 9966-784-24-1 Book 5: Part 1: Ebenergy© Software: E5100 Economy: Pro Det: Individual Annual License Classification: E5110 2,000/Standard: Aca Det: Individual Annual License Classification: E5120 5,000/Prestige: Res Det: Individual Annual License Classification: E5130 10,000/-

Abroad: US $

50 125 250


Yusuf H. Ebrahim

Part 1: Appropriate Roofing & Energy Considerations for Warm-Humid Climates: _____________________________________________________________________________________________ 9966-784-25-X Book 5: Part 2: Ebacoustics© Software: E5200 Economy: Pro Det: Individual Annual License Classification: E5210 2,000/50 Standard: Aca Det: Individual Annual License Classification: E5220 5,000/125 Prestige: Res Det: Individual Annual License Classification: E5230 10,000/250 Building Science Text Book Series: Book 13: Office Practice Documents & Software: E13000 9966-784-97-7 Book 13: Part 1: Ebbank © Software: Financial Management Package: E13100 5,000/125 9966-784-98-5 Book 13: Part 2: Ebfees © Software: Invoicing & Receipts Management Package: E13200 5,000/125 9966-784-99-3 Book 13: Part 3: Ebbq © Software: Mini-BQ, Valuations, Certification & Payment Advices: E13300 5,000/125 Book 13: Part 4: Ebpvouchers © Software: Payment Management Package: E13400 5,000/125 _____________________________________________________________________________________________ Note: 1. These prices are provisional and subject to change without notice and do not represent a commitment on the part of Ebenergy Enterprises. 2. License expires after due date and product should be discarded environmentally safely or renewed for a discounted latest version. 3. Student License: 1 Pac maximum (Single User). 4. Individual License: 1 Pac Maximum (Single User). 5. Academic Institutional License: 30 Pac Maximum (Multiple User): 50% Discount on the group software price. 6. Corporate License: 30 Pac Maximum (Multiple User): 25% Discount on the group software price. 7. Students are entitled to a discount of 50% of the cover price of books (Only) on presentation of their student card. A Copy of the same may be sent with the order form. 8. Allow for 2 Weeks for delivery nationally. 9. Allow for 1 Month for delivery outside Kenya (Abroad). Add:

Postage charges (Per product): Within Kenya: Within East Africa: Kshs. 150/US $ 9

Within Africa: US $ 10

Within Europe: US $ 12

Within America: US $ 14


Yusuf H. Ebrahim



CHAPTER 4:

ORDER FORM:


Yusuf H. Ebrahim


2.0

ORDER FORM:

This order is for:

First Name:………… Surname:…………….Address: ………Postcode: ……City: ……… Country: ………… Tel: ………………… Email: …………… Name & Address of Sender: First Name:………… Surname:…………….. Address: …………… Postcode: ………… City: ……… Country: ……………. Tel: ………………… Email: ………………. Retail Price Guide: EE: Product Within Kenya Abroad: Code: Name: Kshs. US $ Add: Postage: Kshs. US $ Total Amount: Kshs. US $ We attach Cheque No:…… for Kshs. ………..or US $ ………. in the name of “EBENERGY ENTERPRISES”. Bank details: EBENERGY ENTERPRISES, CFC BANK, CFC Centre, Chiromo Road, P.O. Box 72833 – 00200, Nairobi, Kenya. Account No: 0000128821. STERLING POUND (GBP) BANK TRANSFERS: Remitter to transfer funds through: LLOYDS TSB BANK PLC, 71 LOMBARD STREET, LONDON, EC3P 3BS, UK. Telex: 888301 Swift: LOYD GB 2L Fax No: 020 7661 4790 GBP A/C NO: 01004108 For further credit to: Account No: 0000128821 of EBENERGY ENTERPRISES, With: CFC BANK, CFC Centre, Chiromo Road Branch, Swift Code: CFCNKENA UNITED STATES DOLLAR (USD) BANK TRANSFERS: Remitter to transfer funds through: AMERICAN EXPRESS BANK LTD, NEW YORK AGENCY, P.O. BOX 740, NEW YORK, NY 10008, U.S.A. ABA/FEDWIRE: 124071889 Swift: AEIBUS33 USD A/C NO: For further credit to: Account No: 0000128821 of EBENERGY ENTERPRISES, With: CFC BANK, CFC Centre, Chiromo Road Branch, Swift Code: CFCNKENA (For CFC Bank Ltd). Yusuf H. Ebrahim can be contacted: Address: Ebenergy Enterprises, Unit 1, Ebrahim House, 4th Avenue Parklands, P.O. Box 34838, 00100 GPO Nairobi, Kenya. Website: www.ebenergy.net Email: [email protected] or [email protected] or [email protected] Email: [email protected] Tel: +254 020 3751239 Mobile: +254 722513617.

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Yusuf H. Ebrahim

Part 1: Appropriate Roofing & Energy Considerations for Warm-Humid Climates: _____________________________________________________________________________________________ BRIEF OF AUTHOR: Yusuf H. Ebrahim, B’Arch. Hons. (NBI), M’Phil (CANTAB), MAAK., is a lecturer in the Department of Architecture and Building Science (University of Nairobi) with interests in sustainable architecture and planning. He has taught for over 10 years both at the professional and academic circles. He has acted as an external examiner in another local university and served in various capacities on numerous education boards. He started his architectural career as an apprentice with Dalgliesh Marshall in 1979 and eventually rose up the ranks to Junior Partner level of the same. He has won numerous design competitions and seen buildings of different complexities from start to finish and eventually to maintenance. In 1992 he set up Ebrahim Consultants, a multi-disciplinary firm with emphasis with environmental design consultancy. Under her, he has done work on different jobs in Sustainable, Lighting, Thermal, Solar, Acoustic and Ventilation. He prefers to use Passive Systems where applicable and only brings in Active Systems to supplement the same. With others, he has developed different simulation techniques and recently developed softwares using the Excel Format. He is currently undertaking his doctorate degree programme at the University of Nairobi, Department of Architecture and Building Science. With others, he is currently writing books on sustainable architecture and recording his experiences in both the professional and academic world.

EE: Price Guide: BUILDING SCIENCE TEXT BOOK SERIES: Code: Kshs. US $ BOOK 3: TOPICAL THEMES: E3000 Part 1: Appropriate Roofing and Energy Considerations for Warm-Humid Climates: E3100 1,990/- 35 Abstract: The topic of “Appropriate roofing and energy considerations for warm-humid climates” is very extensive dealing with three, though interconnected subjects, i.e. materials, a climate and the energy implication. Each of which demands a study of its own, but which would be too great a task for an M’Phil dissertation. In order to satisfy the latter, the author has limited his study, by restricting his investigations of roofs to a small number of samples, most of which he has observed in his own country (Kenya). This presentation is not supposed to be exhaustive, rather, it is hoped that it may act as a pilot study for future work that the author hopes to conduct at a PhD or M.Sc level. Each of the above three subjects is critical in deciding the rate and direction of development in different countries. In the last twenty years, a lot of controversy has been started due to the misunderstanding between the various planning authorities. The word “development” carries with it numerous interpretations and the author will restrict himself to the environmental and physiological considerations. The purpose of this study is to evaluate the current situation within developing countries, notably those with a warm-humid climate, with the intention of extracting suitable recommendations related to energy, and the eventual production of materials that perform to sound environmental standards. ISBN: 9966-784-19-5 Yusuf H. Ebrahim can be contacted: Address: Ebenergy Enterprises, Ebrahim House, 4th Avenue Parklands, P.O. Box 34838, 00100 GPO Nairobi, Kenya. Website: www.ebenergy.net or: [email protected] Email: [email protected] Tel/fax: +254 020 3751239 Mobile: +254 722513617. _______________________________________________________________________________________________________________ Page: 145 of 145 Building Science Text Book Series: Book 3: Topical Themes:

Yusuf H. Ebrahim

building science text book series

building science text book series

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