OPTIMISATION OF THERMAL PROTECTION IN ... - CiteSeerX

OPTIMISATION OF THERMAL PROTECTION IN RESIDENTIAL BUILDINGS USING THE VARIABLE BASE DEGREE DAYS METHOD Konstantinos T. Papakostas1, Agis M. Papadopoulos2 Χ and Ioannis G. Vlahakis1 1

Process Equipment Design Laboratory Department of Mechanical Engineering, Aristotle University Thessaloniki, GR-54124 Thessaloniki 2

Laboratory of Heat Transfer and Environmental Engineering Department of Mechanical Engineering, Aristotle University Thessaloniki, GR-54124 Thessaloniki

Abstract The optimal degree of thermal protection depends on technical and economic criteria. It is determined by considering the heating and cooling demand of the building and also the feasibility of the investment needed to achieve the aimed degree of thermal protection of the building’s shell. As all these parameters vary with respect to climatic conditions, the fluctuation of cost factors, and the actual way in which buildings are designed and constructed, the determination of an optimal thermal protection is always subject to discussion. A way of approaching this problem is discussed in this paper. The building’s heating demand was determined by applying the DIN 4701 method, whilst its cooling demand according to the CLTD/CLF ASHRAE method. The actual energy consumption arising, in order to cope with these demands, was determined by applying the variable base degree-days method. In order to evaluate the feasibility of the suggested thermal protection, two microeconomic methods were applied, namely the Net Present Value and Depreciated Payback Period. The whole methodology was used to assess a typical Greek single family residential building under varying climatic conditions and for varying degrees of thermal protection, from none at all over the minimal thermal insulation thickness, according to the regulation, and to an enhanced protection. The results, as they are discussed in this paper, demonstrate on the one hand the validity and flexibility of the variable base degree-days method, whilst on the other hand they indicate that the economic feasibility of increasing the standards of thermal protection should not be solely justified by the value of conventional energy saved for current energy retail prices, but also for a reasonable range of prices’ fluctuation.

Χ

Corresponding author: Ass. Professor A.M.Papadopoulos, Tel. +30 31 2310 996015, e-mail: [email protected]

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1. INTRODUCTION Energy consumption in the building sector represents almost 40% of the total energy produced in the European Union [1]. The final energy consumption in the tertiary sector (public and private buildings, hospitals, schools, hotels, etc) and the domestic sector in Greece represents respectively the 29,8% of the final energy consumption of the country, or 38,2 of the primary consumption, whilst it is increasing continuously at an average annual rate of 3.8%. Electricity represents almost 39% of the energy consumption, oil 50% and natural gas some 8%, with a rising tendency. Biomass in rural areas covers the remaining 5% [2].

The energy consumed in buildings is being used for heating,

refrigeration, lighting and other appliances or equipment. The consumption depends on the climatic conditions, the architectural and constructive features of the building, the occupancy and the operational patterns, the various systems of heating and air conditioning, the appliances and the other electromechanical equipment. It is remarkable that residential buildings constitute, according to the National Statistical Service, 73% of the total number of buildings in Greece. Space heating represents 61% of total consumption in residential buildings and refrigeration only 2%, a figure that is expected to treble by 2010 [3]. In the tertiary sector space heating represents 52% of the total energy consumption and air conditioning 17%, also with a rising tendency [4]. Despite the fact that the Thermal Insulation Regulation (T.I.R.) [5] is in effect since 1979, approximately 78% of the building stock features insufficient or no thermal protection at all [6]. This energy consumption features have, apart from the direct effect on the operational costs of buildings, a significant effect on the environment, due to the combustion of gas and oil in central heating plants and also due to the use of electricity for the central or room air conditioning systems. Given the fact that the Greek electrical system is based on lignitefired plants, reducing electricity consumption in the building sector is a necessary step towards the implementation of the Kyoto-Den Haag protocol [7]. Therefore, the necessity of taking measures for saving energy in the building sector becomes eminent in order to reduce the consumption of conventional energy sources, which in fact may offer economic profits not only to building owners but to the national economy as well. This necessity constitutes also a conventional obligation for Greece, according to the European CO2 emissions reduction directive. The acceptance of this obligation has been expressed in the form of the new Regulation for the Rational Use and

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Saving of Energy, according to the related ministerial decision, the publication of which is expected to take place within 2004 [8]. In that line of thought, one of the main measures towards energy saving, applicable to new or existing buildings, is the improvement of thermal protection, by increasing the thickness of thermal insulation on the building’s envelope, as well as by using high performance windows. The improved thermal protection of the buildings’ envelope, will not only lead to reduced thermal losses during winter period, but also to a reduction of the cooling loads in summer, a problem that is becoming more important over the last decade. Finally, the use of low energy consumption lighting systems, together with the application of shading devices, constitute further actions which can contribute to the reduction of energy consumption for air conditioning, despite the fact that they are not directly related to the thermal protection of the building. They were therefore considered in this study. The application of the afore mentioned measures, which constitute the conventional approach of energy conservation strategy, leads to an additional economic investment, the efficiency of which should also be evaluated. The application of thermal insulation in a building in thicknesses exceeding those specified by the regulations, or the replacement of lighting equipment, lead inevitably to higher initial costs. On the other hand, and in particular in new buildings, such measures can lead to smaller, and in that sense less expensive HVAC systems. In any case, the costs for improved thermal protection costs should be able to pay back in an acceptable time period and lead to overall reasonable savings in terms of operational costs for heating, lighting and air conditioning. In this paper is presented the methodology for the energy and economic evaluation of the applications of measures of increased thermal protection in residential buildings, as well as the results concluded by the application of this methodology in a fairly typical detached single-family house. Aim of the paper is the determination of the financially optimal solution, with respect to the level of thermal insulation of the building under varying climatic conditions and for the basic economic conditions prevailing in 2003. In order to demonstrate the approach, the building’s energy loads and consumption values were calculated for the three climatic zones of Greece, from Heraklion on Crete to Thessaloniki in Northern Greece, which present a quite wide range of conditions, as it can be seen from the data in Table 1. These conditions can also be considered as representative for a good

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part of Southern Europe and the conclusions drawn can be applied to relevant situations elsewhere. 2. RESIDENCE CHARACTERISTICS – CALCULATION OF THERMAL INSULATION As an exemplary building a free-standing detached house was chosen, which is featuring a ground floor and a basement. The building has an inclined tiled roof. Both the ground floor and the basement are heated and have a plan area of 98.92 m2 each. The internal height of the ground floor and of the basement is 2.80m. A part of the basement is above ground level and has small openings for the lighting and ventilation of the interior. The plan views of the ground floor, the basement as well as a cross section of the building are presented in pictures 1, 2 and 3 respectively. The building was also considered to have the same constructional characteristics in the three climatic zones in order to enable the direct comparison of results. The methodology was applied for a city for each zone, namely Heraklion for zone “A”, Athens for zone “B” and Thessaloniki for zone “C”. The building is heated by a conventional oil-fired central heating system, which also provides hot water. During the cooling period the desirable internal conditions are achieved by room airconditioners of the wide spread split systems’ type. Both systems are quite representative for Greek residences, but also for such all over the Mediterranean. The methodology was applied for three distinguishable cases of thermal protection of the building, which are the following: I) without thermal insulation, with openings with single glass panels, as they are often observed in southern Greece, but also in older buildings elsewhere. II) with thermal insulation that fulfils the Greek Thermal Insulation Regulation of Buildings for each climatic zone III) with enhanced thermal protection, consisting of thicker insulation in the building’s shell, windows with a fairly low thermal conductivity value and with application of rather conventional, but still frequently missing, sun-protection measures for the openings. The first case represents the majority of the Greek building stock constructed before 1980, whilst the second case is the current ‘business-as-usual’ scenario. Finally, the third case corresponds to the aim of designing buildings with an energy consumption for heating of no more than 50 kWh/m2 a, on a national average [8]. The constructional elements of the building differ, depending on the degree of heat insulation. In the case of the building without thermal insulation, the fabrique of the ground

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floor consists of a single brick wall and armed concrete elements, whilst the basement is solely of armed concrete. The joists, the pillars, the floor and the roof are made of armed concrete. The building’s openings (doors, windows) have aluminium or wooden single glazed windows with a k – value not better than 5.81 W/m2K. In the case of the building being insulated according to the regulation, the fabrique of the ground floor is a double brick one, with stonewool in between, whilst the basement features externally placed extruded polystyrene. The other structural elements are of armed concrete and are insulated with plates of extruded polystyrene. The openings are aluminium framed, double glazed windows and doors, with a relatively good thermal resistance value k = 3.72 W/m2K. Calculating the thickness of the thermal insulation it was ensured that it fulfils the regulation’s requirements. The resulting thermal conductivity values for each structural elements of the building, and for each climatic zone, are presented in Table 2. The resulting initial cost for each case is presented in Table 3, based on representative, average market prices for the year 2003. Case I (i.e. without insulation) was considered as the reference or base-case. The structural elements of the building with enhanced thermal insulation are similar to those of the precious case, with the difference that the thickness of the insulation is now increased and equals 100 mm for the ground floor and 50 mm for the basement. These values are in line with most requirements set by contemporary regulations in other European countries. The openings have an improved thermal resistance value k of 2.32 W/m2K. 3. DETERMINATION OF HEATING AND COOLING DEMAND The calculation of the heating and cooling demand is essential in order to choose and dimension the equipment required for the heating and air-conditioning of the building. It is based on the consideration of the extreme operational conditions with which the system should cope and ensure the establishment of the required comfort conditions. The calculation of the heating demand was carried out according to the DIN 4701 method, whilst the calculation of the cooling demand was based on the CLTD/CLF method by ASHRAE. The building’s internal temperature was considered to be 20°C in the heating period and 26°C in the cooling period. The internal relative humidity was considered to be 50% in both cases. The exterior conditions for the calculation of the loads were selected

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according to the corresponding guidelines and regulations [9]. Furthermore, and for the case of the building with enhanced insulation, it was assumed that all artificial lighting is carried out by means of low consumption - high efficiency systems, in order to minimise the loads caused by lighting. In addition, the openings of the building are considered to be shaded by the roof, which features a longer overhang than in the first two cases, enabling hence the reduction of solar loads. The heating and cooling demand of the building, in terms of specific loads, for the three cases of thermal protection, are presented in Table 4 and 5 respectively. The alleviation of the thermal and cooling demand of the insulated building and the one with enhanced thermal protection, with respect to the base case scenario of the uninsulated one, are presented in Tables 6 and 7 respectively, for the three climatic zones.

4. DETERMINATION OF HEATING AND COOLING ENERGY CONSUMPTION 4.1 Methodology For the determination of the building’s energy consumption for heating and cooling was used the Variable Base Degree Days method [10, 11, 12]. This method is a generalisation of the classical Degree Days method. It maintains its general idea, but the calculation of the degree days is now based on the balance temperature of the building tbal. The balance temperature of the building, is defined as the temperature of the exterior environment, for which, and for a given internal temperature, the total thermal losses are equal to the thermal gains from the sun, the occupants, the lights and the appliances.

K tot ⋅ (t i − t bal ) = Q& gain where K tot is the total factor of thermal losses of the building, in [W/K]. From the above relation it results that:

tbal = ti −

Q& gain K tot

where t bal = the balance temperature of the building, [°C].

Q& gain = the total thermal gains of the building (solar, occupants, lights and appliances), [W]. t i = the internal design temperature, [°C].

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Heating is required when the ambient temperature falls under the balance temperature t bal . The monthly thermal requirement for heating is hence given by the relation:

Q h ,mo = K tot ⋅ DD h ( t bal ) where: DD h ( t bal ) = heating degree-days with base t bal The annual energy consumption for heating is calculated by adding the monthly consumption balues:

Qh ,yr =

j

∑ Qh ,mo

m=1

where I the number of months in the heating period. The method is mainly used for the calculation of energy requirements for heating, but in the case of residential buildings it can provide reliable results for cooling too. The degreedays for Athens and Thessaloniki, for various base temperatures, were calculated by statistical processing of the hourly dry bulb temperature values for the period 1983 to 1992 [11]. The degree-days of the city of Heraklion were calculated by the model of degree-days estimation [11, 13]. Following assumptions were made: 1. As in paragraph 3, the internal temperature was considered to be 20°C, in the heating period and 26°C in the cooling period. The internal relative humidity was considered to be 50% in both cases 2. The residence was considered to be occupied by a four members’ family. 3. For the heating period the whole building was considered to be heated, whilst for the cooling period only the ground floor was considered to be air-conditioned, as the temperature in the basement was assumed to be acceptable even without airconditioning. 4. For the heating period the average ventilation rate for the whole building was considered to be 1 air change per hour, while for the cooling period, and for the ground floor only, 10 air changes per hour. This admission was due to the fact that during the cooling period the tenants usually stop the operation of the airconditioning appliances and open the exterior openings when the exterior air’s temperature is low enough to allow for the building’s natural cooling, even if the exterior temperature exceeds the desirable one (usually 26°C). In that sense, and though it may seem high, the admission of 10 alterations per hour approaches with higher precision the calculation of energy requirements [12].

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5. The efficiency of the heating system was considered to be constant and equal to 0.85, whilst the coefficient of performance of the room air-conditioners was considered to be 2.5. 4.2 Energy consumption for heating The calculation of energy consumption for heating consisted of determining the total thermal losses through the building’s shell, the solar gains, without provisions for sunprotection, the internal gains due to occupants, lighting and appliances. Then the balance temperature of the building was calculated. Based on the balance temperature and the degree-days of heating that correspond to this temperature, the energy requirement in kWh/m2 & a of heated surface was calculated. For the calculation of gross energy consumption, i.e. fuel oil consumption, the average efficiency of the heating system was considered to be the minimum foreseen by regulations, namely 0.85. The results, according to the climatic zone and for the three different levels of thermal protection, are presented in Table 8 [14]. 4.2 Energy consumption for cooling The calculation of energy consumption for cooling consisted of determining the total thermal losses through the building’s shell, the solar gains, without provision for sunprotection, the internal gains due to occupants, lighting and appliances. Then the balance temperature of the building was calculated. Based on the balance temperature and the cooling degree-days which correspond to this temperature, the thermal requirement in kWh/m2 a of heated surface was calculated. To this were added the latent thermal loads due to the occupants, as well as the sensible loads due to appliances and ventilation, resulting in the total thermal requirements of the building for cooling in kWh/m2 a. For the calculation of the electricity consumption (in terms of kWh), was considered the average seasonal coefficient of performance of room air-conditioners, which for an internal air temperature of 26 oC can be regarded as 2.5. The results, per climatic zone and level of thermal protection, are given in Table 9. The alleviation of energy consumption for heating and cooling of the insulated house and the one with the enhanced thermal protection, with respect to the base case scenario, is given in Tables 10 and 11 respectively, for the three climatic zones.

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5. HEATING & AIR CONDITIONING EQUIPMENT The dimensioning of the equipment for heating and air conditioning installations was based on the thermal and cooling demands, for each zone and each scenario of insulation. Each heating system includes the boiler for the production of hot water, the oil burner, the hot water circulator, a triode-mixing valve, the oil tank and the system’s controls. Each air conditioning system includes the split - type room air-conditioners. The installation cost of the heating systems includes the cost of purchase and fitting (transport, work, materials and auxiliary elements). Respectively the cost of air conditioning equipment includes the purchase and the fitting of the appliances. In Tables 12 and 13 are given the installation cost data for both systems, depending on the demands arising in each climatic zone and for each level of thermal protection [14]. For the particular case of residences with enhanced insulation, the purchasing cost of low consumption lighting systems is included, that is approximately 330 €. The constructive measures for sun-protection cause no additional initial costs. As it can be seen from Tables 12 and 13, the heating and air conditioning systems’ cost decreases significantly, particularly when comparing cases I and II. Still, when applying enhanced thermal protection, the reduction in the systems’ cost is not proportional, despite the fact that the reduction of the thermal and cooling demand is important. This occurs because of the lack of appliances (circulators, boilers, but also room air-conditioners) rated small enough for the low demand figures arising. The appliances that have to be selected are therefore overdimensioned, leading to increased, disproportional cost. In that sense, the alleviation of the systems’ cost, with respect to the base case scenario, is not the expected linear one, as it can be seen from the data shown the in Tables 14 and 15 for the heating and air-conditioning system respectively. 6. ECONOMIC EVALUATION OF THE ALTERNATIVE OPTIONS 6.1. Methodology applied The evaluation of alternative investments, such as the thermal protection of buildings, was carried out by applying the Net Present Value and the Depreciated Pay-Back Period methods. As Net Present Value is determined the total net profit gained from the implementation of a particular investment, deduced to constant "present" prices for a

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"zero" time period, which, as a rule, coincides with the beginning of the building’s operation. The Net Present Value of the investment is therefore determined by the relation:

N

Ft

NPV = −Cin + ∑

t =1 (1 + d )

t

+

SVN

(1 + d ) N

where Cin initial investment [€], Ft annual net profit [€], N economic life time of the investment [years], d interest-rate or capital cost rate to present value (capital cost) [%], SVN salvage value (residual value) of the investment at the end of its economic life time Ν[€].

In the particular case the profit results as the difference from the reduction of the energy consumption concerning the base case solution (uninsulated building). Respectively, as initial investment is considered the additional cost of purchasing and fitting the thermal insulation, the improved windows and doors, the heating, air-conditioning and lighting systems. The economic life time is considered to be 25 years and the salvage value of the investment is considered to be negligible. Finally, the capital cost rate was considered to be 4%, a rate that corresponds to the cost of 25 years’ mortgages for the construction or acquisition of residential buildings (as of June 2003). Respectively, and for the same assumption, the Depreciated Pay Back period of the investment results according to the following relation:

DPB =

d ⋅ Cin F ln(1 + d )

− ln ( 1 −

)

An investment is considered to be economically feasible, when the DPB value is according to the investor’s expectations. In practice, this value cannot exceed one third of the economic life-cycle of the investment, which in this case would come up to 8 years [15]. 6.2. Optimisation using economic criteria

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The first conclusion that can be drawn is that defining the optimal solution depends on macroeconomic conditions, as the latter are depicted in the capital cost rates. The monetary stability that prevailed throughout the 1990’s has made this factor a less important one than it used to be in previous times of high inflation [16]. This development is certainly encouraging investments with a longer life time, such as the energy conservation measures in residential buildings. Furthermore, there has been a significant reduction in the costs of insulation materials, at an order of magnitude of some 20% compared to the prices in the beginnings of the nineties [17]. Finally, the feasibility of the options is strongly depending on the expected developments of retail energy prices, as these determine the yield of the investment. With respect to this last parameter, three scenarios were considered. When the increase of retail energy prices (in this case fuel oil) is 4%, i.e. it follows the inflation rate and prices remain in that sense constant, then the economically optimal protection scenario is the second one, as determines by the present Thermal Insulation Regulation. The difference in the results however, when compared to the case of enhanced protection, is a rather marginal one, as the total initial cost is 8.86 €/m2 for zone A, 8.39 €/m2 for B and 5.53 €/m2 for C respectively. On the contrary, for the scenario that the oil price will increase at 6% annually, one comes to the result that the financially more feasible solution, is the case of the building with enhanced thermal insulation, at least in zones B and C. Respectively, when the increase of oil price is 8% annually, then the economically optimal solution for a financial circle of 25 years is the case of strengthened insulation, in all three climatic zones. It has to be pointed out, that the increase in heating oil prices during the period 2000-2003 was slightly higher than 26%, leading to an average annual increase rate of almost 8% [2]. Equally, as it was expected, regarding the Depreciated Pay Back Period of the two possible insulation solutions, the difference between the pay back periods of the improved thermal protection and the one according to the thermal insulation regulation varies between 2 to 8 years, according to the climatic region. It is pointed out that, even in the most unfavourable case, this of the warmer zone C, and with the oil prices increasing according to inflation, the pay back period for the enhanced thermal protection does not exceed the 8 years’ limit. It can, in that sense, is considered to be feasible, especially when keeping in mind that that the investment’s true life time exceeds, as a rule, the

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conventionally assumed one of 25 years. If indeed one contemplates that the real life duration of a residential building, which is at least 50 years, then the results are eloquent in favour of the most enhanced form of thermal protection.

7. CONCLUSIONS The discussion of what ‘sufficient’ thermal protection stands for is as old as the introduction of the first regulations, back in the early 1970’s. The answer depends, as in most optimisation problems, on many parameters, not least on principles. In this paper were discussed a methodological approach for the optimisation of thermal protection and the results of its application for Greek conditions. Factors that were taken into consideration included the additional initial cost required for improving the building’s performance the reduction achieved in thermal and cooling demands, the reductions achieved in dimensioning the heating and air-conditioning equipment and, finally, the savings in energy consumption and the respective costs. These results were determined considering different scenarios of variations for energy retail prices, as this influence the feasibility of enhanced thermal protection, at least from the building owner’s point of view. Considering the impact of retail energy prices, the results have underlined that even in the modest assumption that energy prices follow the inflation rate; the feasibility of an enhanced thermal protection is ensured. Another result that can be highlighted is that, even for the warmest region of Greece and for the more modest oil and electricity cost increase expectations, the solution of an enhanced thermal protection constitutes an economically advisable solution, though not necessarily one appealing to the investor. It was also proven that, even the simple application of the existing Thermal Insulation Regulation leads to a very satisfactory saving of energy and financial resources, especially in the “A” climatic zone, where it constitutes the optimal choice. This is even more important, as the participation of cooling loads in the overall energy budget of residential buildings becomes a steadily increasing part of the buildings’ operational cost. Despite the opposite feeling that was produced by the energy prosperity of the 1990’s, the initial investment needed for thermal insulation seems currently to be more justified than in the past. A contributing factor that cannot be disregarded is the actual decline in the cost

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of insulation materials. Another one lies in the fact that energy prices have not only remained at quite high levels since 2001, but also presented a high volatility. The principle of investing in the present in energy conservation measures during a building’s construction, rather than having to do so in the future in a retrofitting of the building’s shell remains a reasonable one.

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REFERENCES 1.

European Commission 2001, Energy and Transport in Figures, Brussels

2.

National Statistical Service of Greece, Statistical data: Energy, Athens 2002 (in Greek)

3.

Balaras Κ.Α., Droutsa Κ. και Argiriou Α.Α., EPIQR-TOBUS: Evaluation of energy saving measures in multi-storey residential and office buildings, Bulletin of the Hellenic Engineers Chamber, v. 2125, November 2000. (in Greek)

4.

Liveris P., Aravantinos D., Papadopoulos A., Tsakiris N., "Guide on energy conservation in public buildings", technical handbook for the renovation of public buildings in order to improve their energy efficiency, SAVE programme, Thessaloniki, 1996 (in Greek)

5.

Greek Thermal Insulation Regulation, The Government’s Official Paper 362/79, vol 4. (in Greek)

6.

Santamouris Μ., Chrisomallidou Ν., Kleitsikas N., Papadopoulos Α., Tsakiris Ν., ‘Energy rehabilitation of multi-use buildings’, SAVE Programme, CIENE, Athens, 1997.

7.

Regulatory Authority for Energy, Proceedings for the period July 200 – December 2002, Athens, 2004, p.259-263 (in Greek)

8.

Regulation for the Rational Use of Energy and Energy Conservation, The Government’s Official Paper 880/98, Ministerial Decree 21475/4707, 1998. (in Greek)

9.

Technical Directive of the Hellenic Engineers Chamber

2425/86, Installations in

buildings: Determination of cooling loads in residential buildings, HEC, 1987. (in Greek) 10.

Papakostas Κ.Τ., Estimation of heating energy requirements of residences with the variable base degree days method, Proceedings of the 6th National Conference on RES, Institute of Solar Technology, Vol. Α, Volos, 1999. 67-76 (in Greek)

11.

Papakostas Κ.Τ., Contribution to the assessment of energy consumption in heating and cooling systems in Greece, using single and multiples measurement methods. PhD Thesis, Dept. of Mechanical Engineering, Aristotle University Thessaloniki, Thessaloniki, 2001. (in Greek)

15 12.

Kreider J.F and Rabl A., Heating and Cooling of Buildings. Mc Graw Hill Inc., USA, 1994.

13.

Papakostas K.T. and Papadopoulos A.M., Energy requirements for the treatment of fresh air in HVAC systems: A case study for Athens and Thessaloniki, Greece, Int. Journal of Ventilation, in press

14.

Vlahakis Ι., Possibilities for optimising the thermal protection of buildings in the 3 climatic regions of Greece. Diploma Thesis, Dept. of Mechanical Engineering, Aristotle University Thessaloniki, Thessaloniki, 2003. (in Greek)

15.

Papadopoulos A., Theodosiou T. and Karatzas K. (2002), Feasibility of energy saving renovation measures in urban buildings: The impact of energy prices and the acceptable pay back time criterion, Energy and Buildings 34, 455-466.

16.

Chrisomallidou N. and Papadopoulos A. (1995), Feasibility of thermal insulation compared to the requirements set by the Greek regulations; changes taken place over the last decade, Proceedings of the Building Physics Symposium 1995, Budapest, 04-06 October, 147-152.

17.

Papadopoulos A.M. and Papadopoulos M.A. (2001), Contemporary insulating materials and energy design of buildings, Proceedings of the 1st Conference of Building and the Environment, Athens, 17-18 September (in Greek)

16 Table 1. Main climatic data for representative cities of the three climatic zones in Greece [9, 11]

Location

Annual solar irradiance

Heating Degree – days

kWh/m2 1,631

for 18 oC 782

C 32.5

C 24.0

1,581

1,100

34.5

25.0

34.5

25.0

245

1,403

1,725

34.5

24.0

34.5

24.0

169

(horizontal)

Heraklion (Zone A) Athens (Zone Β)

Cooling Degree – days

Design Conditions Cooling o C DB WB 32.5 24.0

DB 1% o

WB 1% o

for 25 oC 225

(Ellinikon airport) Thessaloniki (Zone C) (Mikra airport)

17 Table 2. Heat transfer coefficients of the building elements (W/m2K)

Heat transfer coefficients (W/m2K) Structural element

Without

Thermal insulation

insulation

according to T.I.R.

Enhanced protection

Zone

Zone

Zone

Zone

Zone

A, B, C

A

B

C

A, B, C

2.131

0.700

0.700

0.616

0.323

3.218

0.650

0.650

0.542

0.295

3.218

0.650

0.650

0.542

0.295

Windows

5.815

3.721

3.721

3.256

2.326

Roof

3.179

0.427

0.427

0.427

0.233

3.218

0.680

0.680

0.563

0.563

3.218

0.650

0.650

0.542

0.542

5.815

3.721

3.721

3.256

2.326

5.025

0.700

0.700

0.577

0.577

3.734

0.668

0.668

0.554

0.554

Floors

3.131

1.732

1.13

0.667

0.553

Overall km-value

3.110

0.858

0.792

0.653

0.481

Ground Floor Fabrique (brick walls) Joists (armed concrete) Pillars (armed concrete)

Basement (above the ground) External Walls (armed concrete) Pillars (armed concrete) Windows Basement (in the ground) External Walls (armed concrete) Pillars (armed concrete)

18 Table 3. Initial cost estimation of thermal insulation and fenestration for the single-family detached house in the 3 climatic zones (€/m2)

Climatic Zone

Zone A

Zone B

Zone C

-

-

-

Thermal insulation according to T.I.R.

39.29

39.29

48.28

Enhanced thermal protection

70.87

70.87

70.87

Without thermal insulation

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Table 4. Specific heating demand of the single-family detached house in the 3 climatic zones (W/m2)

Climatic Zone – City

Zone A

Zone B

Zone C

Heraklion

Athens

Thessaloniki


82.1

88.3

128.5


32.1

36.4

43.1


21.6

24.8

35.0

20

Table 5. Specific cooling demand of the single-family detached house in the 3 climatic zones (W/m2)


Zone A

Zone B

Zone C

Heraklion

Athens

Thessaloniki


121.8

137.9

125.8


88.9

92.9

87.9


80.8

82.9

80.8

21 Table 6. Heating demand reduction with respect to the uninsulated construction for the 3 climatic zones (%)


Zone A

Zone B

Zone C

Heraklion

Athens

Thessaloniki


61.0

58.8

66.5


73.6

71.9

72.8

22 Table 7. Cooling demand reduction with respect to the uninsulated construction for the 3 climatic zones (%)


Zone A

Zone B

Zone C

Heraklion

Athens

Thessaloniki


27.0

32.7

30.0


33.7

40.0

35.8

23 Table 8. Specific heating energy consumption (kWh/m2 a) and fuel consumption (l/m2 a) for the 3 climatic zones


Level of protection

Without thermal insulation Thermal insulation according to T.I.R. Enhanced thermal protection

Zone A

Zone B

Zone C

Heraklion

Athens

Thessaloniki

Thermal

Electrical

Thermal

Electrical

Thermal

Electrical

energy

energy

energy

energy

energy

energy

consum.

consum.

consum.

consum.

consum.

consum.

117.50

13.82

174.8

20.57

256.90

30.23

35.90

4.23

54.4

6.40

73.30

8.62

24.20

2.84

37.1

4.37

57.90

6.82

24 Table 9. Specific cooling energy consumption (kWh/m2 a) and electrical energy (kWhel /m2 a) for the 3 climatic zones


Level of protection

Zone A

Zone B

Zone C

Heraklion

Athens

Thessaloniki

Thermal

Electrical

Thermal

Electrical

Thermal

Electrical

energy

energy

energy

energy

energy

energy

2

Without thermal insulation Thermal insulation according to T.I.R. Enhanced thermal protection

2

2

2

2

kWh/m a

kWhel /m a

kWh/m a

kWhel /m a

kWh/m a

kWhel /m2 a

71.10

28.40

97.60

39.10

84.10

33.60

42.90

17.20

46.40

18.60

36.90

14.80

36.00

14.40

37.30

14.90

29.90

12.00

25 Table 10. Heating energy consumption reduction for the 3 climatic zones (%)


Zone A

Zone B

Zone C

Heraklion

Athens

Thessaloniki


69.4

68.9

71.5


79.4

78.8

77.5

26 Table 11. Cooling energy consumption reduction for the 3 climatic zones (%)


Zone A

Zone B

Zone C

Heraklion

Athens

Thessaloniki


39.7

52.4

56.1


49.4

61.8

64.4

27 Table 12. Cost estimation of the heating system for the 3 climatic zones (€/m2)


Zone A

Zone B

Zone C

Heraklion

Athens

Thessaloniki


23.72

24.83

29.62


23.72

24.83

29.62

Strengthened thermal protection

17.33

17.55

18.03

28 Table 13. Cost estimation of the air-conditioning system for the 3 climatic zones (€/m2)


Zone A

Zone B

Zone C

Heraklion

Athens

Thessaloniki


23.67

24.86

23.67


23.67

24.86

23.67


17.60

17.93

17.08

29 Table 14. Central heating system’s cost reduction for the 3 climatic zones (%)


Zone A

Zone B

Zone C

Heraklion

Athens

Thessaloniki


26.7

29.3

39.1


30.5

33.4

41.2

30 Table 15. Air-conditioning system’s cost reduction for the 3 climatic zones (%)


Zone A

Zone B

Zone C

Heraklion

Athens

Thessaloniki


25.7

27.9

27.8


29.3

32.7

29.3

31

Figure 1. Plan view of the ground floor

32

Figure 2. Plan view of the basement

33

Figure 3. Cross-section