Jun 28, 2017 - consumption of low income multiple housing using a holistic approach, ... reduce its energy consumption and carbon footprint, improve indoor ...
Accepted Manuscript Title: Minimizing the energy consumption of low income multiple housing using a holistic approach Authors: A. Synnefa, K. Vasilakopoulou, G.-E. Kyriakodis, V. Lontorfos, R.F.De Masi, E. Mastrapostoli, T. Karlessi, M. Santamouris PII: DOI: Reference:
S0378-7788(17)31354-3 http://dx.doi.org/doi:10.1016/j.enbuild.2017.07.034 ENB 7774
To appear in:
ENB
Received date: Revised date: Accepted date:
18-4-2017 28-6-2017 12-7-2017
Please cite this article as: A.Synnefa, K.Vasilakopoulou, G.-E.Kyriakodis, V.Lontorfos, R.F.De Masi, E.Mastrapostoli, T.Karlessi, M.Santamouris, Minimizing the energy consumption of low income multiple housing using a holistic approach, Energy and Buildingshttp://dx.doi.org/10.1016/j.enbuild.2017.07.034 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
Minimizing the energy consumption of low income multiple housing using a holistic approach A. Synnefaac, K. Vasilakopouloua, G.-E. Kyriakodisa,, V. Lontorfosa, R.F. De Masib, E. Mastrapostolia, T. Karlessia, M. Santamourisa,c a
Group Building Environmental Studies, Physics Department, National and Kapodistrian University of
Athens, Athens, Greece b c
University of Naples Federico II PiazzaleTecchio, 80, 80125 Napoli, Italy
The Anita Lawrence Chair in High Performance Architecture, Faculty of the Built Environment,
University of New South Wales, Sydney, Australia
Abstract The present paper describes a holistic energy efficient retrofit of low income multiple social housing located in Athens, Greece. A holistic analysis was conducted in order to determine the optimum retrofit plan that includes innovative and state of the art commercially available technologies, passive techniques as well as renewable energy sources, aiming to reduce its energy consumption and carbon footprint, improve indoor environmental conditions and be cost effective at the same time. An extensive experimental campaign including air leakage measurements, thermal imaging, energy consumption and indoor environmental quality measurements was conducted before and after the implementation of the retrofit. In addition, advanced building simulation, occupant surveys and socioeconomic analyses were performed in order to evaluate the impact of the retrofit and estimate specific performance indicators.
Keywords: energy savings, thermal comfort, refurbishment, residential building, innovative technologies.
1. Introduction The building sector representing the largest industrial sector in economic and resource flow terms has been the focus of European energy and environmental protection policies and regulations in recent years. Buildings in Europe are responsible for 40% of total energy consumption and 36% of CO2 emissions while the corresponding global rates are 40% and
38% respectively [1, 2]. The European Commission has set specific targets to reduce energy consumption by 20%, CO2 emissions by 20% and provide 20% of the total energy share with renewable energy by 2020. The European Union has also committed to 80-95 % GHG reduction by 2050 as part of its roadmap for moving to a competitive low-carbon economy in 2050 [3]. Moreover, the Energy Performance of Buildings Directive [4] requires all new buildings to be nearly zero-energy by the end of 2020. New buildings with implemented energy management systems and sustainable energy technologies are able to meet these targets. However, at least 75% of the building stock (70-80% of this is residential) is already in existence and it will be present in the next decades. Studies on European buildings have shown that more than 40% of residential buildings have been constructed before the 1960s when energy building regulations were very limited or non-existent [5]. This has a serious impact in their energy performance and carbon footprint. It has been found that older buildings consume on average 5 times the litres of heating oil per square meter per year that new buildings consume. In Greece, residential buildings represent about 79% of the building stock and consume about a quarter of the total final energy consumption. About 58% of the dwellings were constructed before the 80s when the first thermal insulation regulation was adopted [6]. Greek households have been found to present significantly higher energy consumption compared to countries with colder climates like Denmark, Germany and the Netherlands [7]. Apart from the energy and environmental impacts related with the poor quality of the residential building stock, energy poverty, defined as the difficulty or inability of a household to afford covering in an adequate manner its energy needs, due to high cost of energy, low household income and building' s energy inefficiency, or a combination of them [8], has become a serious problem in Europe affecting mainly the vulnerable population. It has been estimated that rates of fuel poverty range from 9.7% to 15.11% of the European population [9]. In Greece, energy poverty is a significant problem. Low income population in Greece lives in poor quality households (no insulation, double glazing etc.) and as a result they have to spend almost the double energy quantity for heating and cooling per square meter and inhabitant, to satisfy the basic energy needs of the houses [10]. Moreover, the financial crisis that Greece is facing has worsened the problem of energy poverty. As the income per capita has considerably decreased due to austerity measures and as the fuel prices have augmented most of the low income households have used their heating system for a minimum period or they have not used it at all resulting in a significant reduction in their energy consumption as reported by a recent study [11].
This financial inability of the low income population to satisfy their heating and cooling needs has a serious impact on the indoor environmental quality of the low income households. Measurements conducted in 43 low and very low income houses during the winter of 2012–2013 in Athens have shown that indoor temperatures are much lower than the minimum threshold values set for comfort and health purposes reaching values as low as 5°C [12, 13]. Regarding summer conditions, a study conducted in Athens during the heat wave of 2007, including the monitoring of indoor temperature of 50 low income households, showed that that indoor temperature as high as 40◦C occurred while the average indoor minimum temperature was always above 28◦C. For almost 85% of the heat wave’s period indoor temperatures were found to exceed 30◦C [14]. Many studies have shown that inappropriate indoor environmental quality conditions place the health of humans at risk, and have a serious impact on mortality [15,16,17,18]. It is evident that immediate actions need to be taken to improve the quality and resilience of the building stock. Therefore, retrofitting of residential buildings represents a major challenge and a holistic solution for retrofitting has the highest potential to transform existing and occupied buildings into energy-efficient buildings, presenting major opportunities for cost-effective investments in efficiency. The objective of this paper is to present the activities related with the energy efficient retrofit of a low income multiple social housing located in Athens, Greece and to demonstrate its effectiveness in reducing energy consumption and carbon footprint, improving indoor environmental conditions and being cost effective at the same time. The optimum retrofit scenario is identified through a holistic approach that was carried out in the design phase and is presented here. The methodology and results of the evaluation of the impacts of the retrofit that was performed by experimental measurements, advanced simulation techniques, occupant surveys and economic analyses are reported. More information on the retrofit activities and occupants’ interviews can be found in [19]. This work has been implemented in the framework of an FP7 project called “HERB: Holistic energy-efficient retrofitting of residential buildings” [20] that aims at the creation of a framework of development, demonstration and dissemination of very innovative and costeffective energy efficiency technologies for the achievement of very low energy residential buildings through a holistic retrofit process.
2. Description of the demonstration building The building to be retrofitted is situated at the Municipality of Peristeri, approximately 4.5km from the city center, in the western part of the Athens. This area is characterized by high density plots, lack of green spaces, heavy traffic conditions as there are some major road axes running by the area and it is located at the "entrance" of an industrial zone. The housing stock is of poor quality (a large part was illegally built), while the area lacks basic infrastructure and has serious environmental problems. Research has shown that the UHI effect in the area is important [21]. It is one of the most populous municipalities in Greece, inhabited mainly by medium and low income people and has high rates of unemployment. The selected building is one of the seven buildings built in the early 70’s by the Ministry of Social Services, in order to house refugees. It consists of two identical rectangular but independent semi-detached, 7-storey apartment buildings, one of which has been selected for retrofit. The building under study has a total area of 1,160 square meters and has 15 apartments, each of which belongs to a different owner. Each apartment has an area of 69 square meters approximately and consists of four main rooms -living room, kitchen and two bedrooms. The plan of one of the apartments is shown in Figure 3. Only one of the apartments (the one on the ground floor which was intended to be used by the building manager), is different, as it is of much smaller area and different layout. The façade of the building, where the main entrance is located, is considered to be the north-east facing. The apartment building is made of reinforced concrete and brick walls, without any insulating material and a concrete roof and ceiling. The windows and balcony doors that were initially implemented had single glazing and wooden frames. In recent years, some of the owners have replaced some windows and doors by double glazing and aluminum frame ones. Representative thermal characteristics of the building elements are found in Table 1& 2. The apartments are heated by a central oil boiler, without having the opportunity to adjust the interior temperature to the desired levels by an individual control. Since 2013, the central heating has not been used due to the lack of financial resources of the residents. Instead, some residents have installed air-conditioning units that they use for both heating and cooling and other portable devices for heating (e.g. portable electric radiators) and cooling (e.g. electric fans).Most apartments are lit by domestic type luminaires, housing incandescent or compact fluorescent lamps with a mean power between 4-13 W/m2.
3. Implementation of the retrofit
A design methodology involving a holistic analysis was followed in order to determine the optimum retrofit plan which was fundamentally centralized around the specific performance targets that the building to be retrofitted should meet:
energy savings of 80%,
reduction of CO2 emissions of 60%,
global energy consumption of 50 kWh/m²/year,
energy saving for lighting of 80%,
occupant satisfaction
a pay-back period of between 2-5 years compared to current state of the art,
compliance with national standards.
The holistic analysis consists of an iterative process that considers the energy, environmental and socioeconomic performance of the proposed solutions. The first step consisted of the initial design (baseline case) that was determined by survey analysis of the building. The baseline Case (pre retrofitted building) was analyzed and compared to several other retrofit scenarios including innovative technologies and other state of the art commercially available energy efficient and sustainable energy technologies. For each retrofit scenario analysed, the results were examined to see if they fulfill the specific energy, environmental and cost targets. If the target/s were not met the process was repeated with a new set of technologies and solutions until the optimum retrofit scenario in terms of energy, environmental and cost performance was determined.
In order to perform the holistic analysis advanced simulation techniques have been used including dynamic energy modeling, comfort modelling (PMV-PPD), carbon emissions savings calculations, application of economic calculation theory to analyse the financial feasibility of the solutions., other analyses for assessing the innovative technologies (e.g. PV modeling (PVGIS), custom model for energy efficient lighting).
The results of the holistic analysis showed that energy efficiency technologies were the most effective in relation to the retrofit approach (roof & wall insulation, replacement of single glazed windows with double glazing) followed by the application of passive and low cost measures (night ventilation, ceiling fans, shading, smart coating). Although useful, renewable technologies were less effective with respect to impact (PVs on SE facade). The following figure shows the percentage of energy savings and CO2 emissions saved by the combination of the previously mentioned technologies
The optimum retrofit plan was identified and consisted of the following interventions:
envelope insulation: implementation of exterior insulation of walls (rockwool panels) and roof (flat Inverted roof material, comprised of extruded polyethylene topped with coated ceramic tiles with cool properties). The details of the pre and post retrofit envelope properties are described in Table 1.
Efficient windows: replacement of all the old windows and glass balcony doors with new windows, with double glass panes, aluminium frames and thermal stops. The following table shows the pre and post retrofit window properties. Smart coating: application of smart photocatalytic coatings on the building envelope. The coating has improved anti-pollutant, self-cleaning and cool (increased solar reflectance) characteristics. The photocatalytic property of the plaster is estimated to an average of 12% in oxidation of NOX to NO3- and the solar reflectance of the coating is estimated to be 0.5.
LED lighting: Replacement of all the inefficient lamps in the building with LEDs. Table 3 includes the characteristics of the lamps before and after the retrofit.
PV panels: installation of PV panels on the South-East Façade, in order to cover part of the energy consumed in the building. Table 4 includes details about the proposed panels.
Energy efficient light system: Installation of the innovative energy efficient lighting system that was developed by NKUA on the roof of the communal stairs leading from the seventh floor to the roof. It consists of integrated light pipe (diameter of 0.30m and height of 0.60m) and LED system ( 8 GU10 LED lamps of 5W each that are dimmed according to the daylight coming from the light pipe) including smart control for energy savings and to maintain a stable desired lighting output. The innovative energy efficient lighting system is described in detail in [22] Ceiling fans: Installation of one ceiling fan in each of the 15 apartments of the building.
Exterior shading: Installation of external shading devices (awings) over all the SW windows, protecting them from the sun, as well as from the rain as the South-West facing windows of the apartments receive great amounts of solar radiation, which increases the thermal load and the need for mechanical cooling.
Night ventilation: Night ventilation during the warm period of the year was proposed as it would decrease the interior temperatures in the apartments. For night ventilation a value of 0.4ACH (including infiltration) has been considered. This technique did not include any technologies but was suggested to the tenants and training was provided to them on how to perform effectively this technique.
The results have shown that for the optimum scenario the energy savings reach 80.3% and the CO2 emissions savings reach 80.3%. The energy consumption for the pre retrofit case was estimated to be 154.5kWh/m2/y while for the post retrofit case was 30.5kWh/m2/y, in primary energy. In terms of comfort the PMV –PPD analysis that was performed showed that the application of retrofit technologies significantly improves winter and summer internal conditions. The results of the holistic analysis have shown that the installation of the retrofit technologies satisfy the project targets. The proposed interventions as described above have been implemented during July 2015 – March 2016.
4. Methodology This section describes the methodology that was followed in order to evaluate the performance of the building in terms energy, comfort, environmental impact, cost effectiveness and occupant satisfaction using both experimental and theoretical approaches.
4.1 Experimental investigation of the building’s performance An experimental campaign has been set up with the aim to collect data on the buildings’ energy and environmental performance before and after the retrofit. The monitoring activities included the installation of sensors in the apartments of the buildings for continuous measurements, in situ measurements conducted on specific days, laboratory measurements and collection of data from meteorological stations. The monitoring period started in February 2014 and finished in December 2016 covering different climatic
conditions; heating, intermediate, and cooling season for both the pre and post retrofit conditions of the building following the same monitoring protocol. More specifically, in order to monitor the energy use smart meters have been installed in all apartments and measured values were displayed and gathered in a web portal for remote access. Temperature and relative humidity data loggers were installed in at least 2 rooms in each apartment to monitor the thermal comfort conditions in different thermal zones. Moreover, air quality sensors were installed in each apartment measuring the concentration of CO2 and VOCs on a continuous basis. Figure 4 shows the location of installed sensors for 2 representative apartments.
Additionally, in situ experiments were conducted in order to assess the thermal comfort under hot and cold conditions by measuring the mean radiant temperature and the air velocity. Lighting measurements in the building under representative outdoor conditions were also performed. The condition of the building envelope was assessed using infrared thermography. In order to determine the air tightness, air leakage and ventilation rates of the building three apartments were chosen as they were representative of the conditions prevailing in the building a)one representing low air tightness, with old type wooden frames and single glazing b) one representing medium air tightness, Mixed situation: some old type wooden frames and single glazing and some aluminium frames and double glazing and c) one representing good air tightness with new type aluminium frames and double glazing. The blower door method was used to estimate the air tightness of the building in accordance with EN13829 [23]. Air leakage measurements have been performed in collaboration with the University of Nottingham using a novel pulse leakage tester. This is a novel technique developed at the University of Nottingham that subjects the building envelope to a known air volume change of a short period of time (1.5 s) using an air compressor, solenoid valve, nozzle and control unit. This generates a flow rate through the adventitious openings that in turn creates a pulse in the internal pressure, characteristic of the building's leakage. This method provides a measure of the air tightness of the building at a pressure of 4Pa, which is considered a more realistic pressure condition than conventional steady state measurement at 50 Pa. Due to short time operation, the technique minimizes the effects of wind and buoyancy force and has proven to be highly repeatable [24]. To evaluate the indoor air quality under conditions of natural ventilation, the air change rate has been determined through standard tracer gas measurement. Meteorological data were collected from nearby meteorological stations and include hourly values of the following
parameters: outdoor temperature, outdoor humidity, solar radiation (total and diffuse), wind speed and direction, provided by the National Observatory of Athens. In addition, post retrofit, several additional monitoring activities took place in order to evaluate the performance of the installed technologies and solutions. a. Energy efficient lighting system The methodology for the evaluation of the innovative energy efficient lighting technology consists of a) Illuminance measurements before and after the retrofit and b) Occupant survey to evaluate the tenants’ satisfaction from the lighting environment & acceptability of the technology. Natural and artificial lighting measurements (Interior & exterior horizontal illuminance) were performed in the space where the lighting system was installed, before and after the retrofit during several days representing different lighting conditions and also during the night. The points where measurements were performed are shown in Figure 5.
Furthermore, the RELUX software was used to depict lighting levels in 3D space due to the installed lighting system.
b. cool & photocatalytic materials The methodology to assess the cool and photocatalytic materials that have been installed on the building i.e. a) Roof insulation consisting of extruded polystyrene topped with coated ceramic tiles with cool properties and b) photocatalic plaster applied on the facades of the building, consists of measuring the solar reflectance of the installed material. The solar reflectance of the installed materials was estimated in the laboratory using samples provided by the manufacturers. Furthermore, a sample of bituminous membrane representing the pre retrofit case was obtained from the market. The spectral reflectance of the samples was measured using UV/VIS/NIR spectrophotometer (Varian Carry 5000) fitted with a 150mm diameter, integrating sphere (Labsphere DRA 2500) that collects both specular and diffuse radiation. The reference standard reflectance material used for the measurement was a PTFE plate (Labsphere). Measurements were conducted according to ASTME903 [25]. Spectral reflectance data were used to calculate the solar reflectance of each sample. The calculation was carried out by weighted-averaging, using a standard solar spectrum as the weighting function. The spectrum employed is that provided by ASTME891 [26]. The photocatalytic activity of the plaster was measured as % oxidation of NO to NO2 and ΝΟ3- according to ISO DIS 22197-1 [27]: by the Nanofunctional and Nanocomposite
Materials Laboratory of National Center for Scientific Research “Demokritos” as reported in [28]. The radiation used was UV-Α with maximum intensity at 350 nm. The experimental conditions are:Irradiation : 10 W/m2, Gas flow rate : 3L/min, Concentration of pollutant gas : 1 ppm, 50% RH.
c. PV system The performance of the installed PV system consists of measurements through the inverter that is installed to the basement of the building. The direct approach is through a logger that will be connected to the already installed grid of smart meters. PV systems’ evaluation through monitoring could not start within 2016 as the PVs aren’t yet connected to the national network. The evaluation was performed via simulation.
An overview of the parameters measured and the corresponding measurement methods and instrumentation can be found in Table 6.
4.2 Advanced simulation techniques to estimate the global energy savings With the aim to estimate the global energy savings as well as other indicators of the building’s performance, avoiding differences in the boundary conditions (climatic conditions, user behavior etc.) between the pre and post retrofit case, advanced simulation techniques have been used. A specific methodology has been developed based on relevant ASHRAE and ISO standards [29,30] that consists of using the collected experimental data to calibrate a numerical simulation model developed to predict the thermal performance of the building before and after the retrofit. The model is then validated using a different set of experimental data and it is examined if specific performance criteria are met. In order to calculate the energy savings a whole building calibrated simulation method has been developed which is based in a multi-zone energy model, dynamic simulation with a 8760 hours weather file, using Design Builder software. Two independent simulations have been carried out representing the baseline scenario (pre retrofit building) and the post-retrofit respectively. The input data for the model (e.g. geometric data, thermal characteristics, user behavior etc.) were obtained through building audits, interviews with occupants and data collection. The calibration of the models under free-floating conditions. Two measured air temperature data sets, one for the pre-retrofit (15/9/2014 – 31/10/2014) and one for the post-retrofit (01/03/2016 – 30/04/2016), were used for a two-phase process. The calibration phase corresponds to 21/9 – 2/10 and 1/4 – 15/4 periods respectively. During these periods
the building is not heated or cooled and it is possible to define the accuracy of the model’s thermophysical properties and infiltration rates. The correlation between measured and predicted values is up to 77% and 71% respectively. The final tuning of the models developed was done by adjusting parameters such as internal shading, ventilation rates and schedules, while internal gains were also taken into account. The models were finalized and tested for a different period again without a heating or cooling system. The validation process presented a strong correlation between measured and predicted values reaching 86% and 90% for each scenario respectively. The comparison between measured data and the outputs of the model simulation correspond to hourly data. The acceptable tolerances are measured by the statistical indexes MBE and CV (MSE). According to the methodology a CV-RMSE below 30% and MBE below 10% on an hourly basis ensures a validated model. After calibration, fine tuning and validation both pre and post retrofit models were found to meet the acceptable tolerances (CV-RSME/MBE values were 12.5%/6.8% for the pre-retrofit model and 6.5%/1.8% for the post retrofit model) and have been used for the estimation of global energy savings using the same climatic data and user behavior for the pre and post retrofit case.
4.3 Financial calculations One of the main objectives of the retrofit project was to assess the cost effectiveness of the project. A socioeconomic model was developed with the aim to estimate the payback result of the retrofit solution implemented consisting of innovative technologies, compared with the payback of the investment on state-of-the-art energy efficient technologies that could be adopted rather than the innovative technologies. In addition, the tool estimates the cost effectiveness of the retrofit in terms of cost saved energy (defined as the average net costs incurred to reduce one kWh which are compared with the average end-user energy cost (estimated as a weighted average based on energy consumption perfil and energy prices). The inputs include information on the building (e.g. floor/conditioned area), the HERB technologies and solutions data (type, quantity, lifetime, costs), the state of the art technologies (type, payback period), other project costs, the budget of the retrofit, energy consumption and production data for the pre and post retrofit building, energy prices. This socio-economic model is built on a life cycle cost basis and is implemented in an Excel Platform. This tool was used for the retrofit both during the holistic analysis in order to determine the optimum retrofit scenario and after the retrofit in order to estimate the cost effectiveness of the retrofit. It should be noted here that in order to perform the
calculations with the socioeconomic tool for the retrofit, the real costs of the retrofit have been used as they are recorded in the invoices and receipts. The information on the state of the art technologies is based on input data given by the relevant market actors. Also the input value for the cost of electricity is considered to be 0.179Eur/kWh [31].
4.4 Occupant surveys The tenants’ perception of the quality of their indoor environment before and after the retrofit as well as their views and satisfaction on the retrofit and the technologies and solutions installed in their apartments and building has been documented via occupant surveys. Two questionnaires have been developed one for the situation before and one for the situation after the retrofit and have been distributed to the occupants of the building. Both questionnaires include 7 sections with the same questions falling in the categories of general questions, questions related to perception of the occupants about their indoor environment, thermal comfort, indoor air quality, lighting, acoustics and other issues and there was space for the tenants to make comments. The post retrofit questionnaire included an additional section on the occupants’ acceptability of the installed technologies and solutions and their satisfaction regarding the retrofit. The questionnaires did not contain information on the identities of the persons who filled them in and they were distributed and collected by the building manager. In total 16 people have participated in the pre retrofit survey and the same 14 in the after the retrofit one (2 people were unavailable to participate again during the post retrofit survey). This means that the pre and post retrofit results can be compared. In addition, the building has 7 floors and 15 apartments. Occupants from every one of the 7 floors (apart from the 4th who were not there during the survey period) have participated in the survey, so the whole building is well represented.
5 Experimental results This section reports the main findings of the experimental campaign. As measurement results of the pre and post retrofit condition cannot directly be compared to due to the differences in the boundary conditions (different climatic conditions, different occupant behavior), the main purpose of this section is to provide a qualitative evaluation of the building’s performance.
5.1 Evaluation of the building fabric Using infrared thermography several problems of the building envelope before the retrofit have been identified with most prominent being the important heat losses in winter and heat gains in summer because of the lack of insulation and the thermal bridges (Figure 6A). In addition, the infrared inspection around the window’s frame evidenced also air leakages and infiltrations (Figure6B) which have been verified by the air tightness measurements and also the occupant surveys.
Moreover, the roof of the building was not insulated and covered by dark bituminous membrane, reaching, as a result, high surface temperatures under hot summer conditions. Surface temperatures of the roof slab exceeding 50°C have been recorded during summer indicating the overheating of the building (Figure 7, left part).
Post retrofit, the insulated solar reflective roof has a better thermal performance with observed surface temperatures significantly lower compared to the initial condition (Figure 7, right part). The albedo increase of the roof from 0.13 to 0.58 caused an average surface temperature decrease of approximately 15°C during the summer season under clear sky conditions. The installation of envelope insulation resulted in a significant decrease of the problems of thermal bridges and in the uniformity of the envelope in terms of thermal performance (Figure 8A). Consequently, thermal comfort conditions inside the apartments have significantly improved and the temperatures fluctuations throughout the day.
In parallel, after the retrofit, the single glazing wooden or old type aluminum frame windows were replaced by double glazing energy efficient aluminum frames. Thermal images of the windows’ frames (Figure 8B) showed that the problem of air leakages and infiltrations is solved. This was also verified by the results of the air leakage rate measurements conducted with the novel pulse leakage tester in collaboration with the University of Nottingham. The results show significant reductions of air leakage after the envelope interventions in the apartments 1 and 3 that originally had wooden frames and single glazing. For the apartment 2 the difference between the pre and post retrofit case is not significant. This was expected as in this apartment the air tightness was good due to the aluminium frames and double glazing windows that the tenants had already installed in the pre retrofit situation.
The results of the blower door test follow a similar pattern indicating that the air tightness of the building has significantly improved after the retrofit. Moreover, the results obtained from the ventilation measurements using tracer gas techniques, corresponding to the infiltration scenario, show that the post retrofit values are lower than the pre retrofit case indicating the significant effect of increased air tightness due to the envelope interventions.
5.2 Energy performance The analysis of the pre and post retrofit monitoring data has demonstrated that the technologies and solutions installed in the retrofitted building have contributed to a significant decrease in the energy consumption of the building. The results presented below correspond to a representative apartment on the top floor, as it is highly exposed to outdoor conditions. The energy signature of the building defined as the total energy consumption versus the average outdoor temperature for each day of the year is calculated, and then plotted in the same graph (Figure 10). For both pre and post retrofit conditions two graphs have been created, one for the heating and one for the cooling period.
The energy signature graphs before the retrofit present an evident correlation between energy consumption and the outdoor temperature both for the heating and the cooling season indicating that the indoor environment of the building is vulnerable to outdoor conditions mainly due to the lack of insulation, low levels of air tightness etc. More specifically, when the outdoor temperature decreases during winter the energy consumption is significantly increased. Although the energy consumption of the building is not very high due to the lack of heating and cooling systems the analysis has shown that when the outside temperature drops in winter to e.g. 10°C the energy consumption doubles. During the cooling season when the temperature increases so does the energy consumption to meet cooling demands. The energy signature for the heating period after the retrofit, presents a different situation. The relation between the outdoor temperature and the energy consumption is not as evident indicating that the interventions implemented during the retrofit were successful in thermal proofing the building and improving the thermal comfort conditions indoors. The cooling period presents almost similar behavior although an increasing trend appears when the outdoor temperature exceeds 31°C.
The monthly energy consumption is a representative index to estimate potentially the possible energy reduction due to the retrofit. It should be noted that the energy consumption apart from heating, cooling and DHW includes lighting and appliances. Figure 11 depicts the monthly energy consumption (January-August) of the examined apartment for both pre and post retrofit conditions and the relative decrease of it. Although pre and post retrofit energy consumption results cannot directly be compared as the boundary conditions (climatic data, user behavior etc.) are different, a reduction in the energy consumption is evident indicating the impact of the retrofit solution in reducing the building energy consumption.The maximum reduction of energy consumption is achieved during January and reaches a value of 54%.
5.3 Thermal comfort The statistical analysis of the collected temperature and relative humidity data indicates an improvement in thermal comfort conditions inside the apartments. The boxplots in the following figures represent a statistical distribution of the measured indoor temperatures of 3 representative apartments and also the outdoor temperature. In these figures the median, lower and upper quartile values are represented as well as the extent of the rest of the data.
Concerning the heating period, Figure 12 depicts that the indoor temperature variation for all the apartments in the post retrofit condition which is minimized compared to the pre retrofit condition despite the fact that the outdoor temperature fluctuations are higher. Moreover, indoor temperatures are maintained at higher levels and close to the comfort zone and extreme minimum temperature values are not observed. This is due to the improvement of the envelope. During the cooling period, high indoor temperature values are observed both pre and post retrofit and temperature fluctuations exist in the post retrofit case.Apart from the differences in the outdoor temperature, June 2016 was hotter than June during the pre retrofit monitoring, this can be easily explained by the fact that occupants during summer use natural ventilation (cross or single side ventilation and night ventilation) in order to cool their houses when the outdoor temperature is lower or just to take advantage of the cooling effect of the drafts created. Relative humidity data are quite similar in the different apartments. The maximum values during the winter months for the pre retrofit case tend to saturation level while for the post retrofit significant improvement has been observed. Although, high and low values of relative humidity are observed also post retrofit, relative humidity presents a more stable
state and stays close to the comfort range 30-50% for the majority of time during both summer and winter. In addition, the percentage of hours of discomfort defined as the % of hours with indoor temperatures outside the thermal comfort range was calculated for the heating, cooling and intermediate period for the pre and post retrofit cases. According to Greek regulations the thermal comfort zone is considered to be between 20°C-26°C, however we have considered the comfort zone to be between 19°C-27°C which is acceptable and representative for Greek households.
During winter and the intermediate season, the figures show significant reduction in the hours of discomfort after the retrofit indicating the effectiveness of the retrofit solution in improving thermal comfort conditions inside the apartments. This is very important if we consider that due to financial restrictions the use of HVAC systems is limited. For January, the value does not seem to be significantly improved. However, if we examine the profile of the indoor temperature for the apartment during January for the pre and post retrofit period (Figure 14), it is observed that although post retrofit, the values were below the comfort limit set to 19°C, the indoor temperature fluctuations were minimized during this period compared to the pre retrofit and the temperatures inside the apartment were maintained around 18°C. The minimum values recorded in the apartment post retrofit were close to 16°C while pre retrofit values as low as 13°C were recorded. All this indicated significant improvement of the thermal comfort conditions. During the summer period, the levels of the hours of discomfort are comparable. As it was explained previously this is due to the differences in the outdoor temperature between the pre and post retrofit periods but also due to the ventilation conditions in the apartments. Moreover, if we consider that post retrofit the occupants had used the installed ceiling fans (as they stated in the surveys) the comfort zone would be extended by 3°C [32, 33] resulting in reduced % of discomfort hours equal to 37%, 45% and 53% for June, July and August respectively.
5.4 Lighting The illuminance values measured in the apartments before the retrofit are considered to be moderate for domestic environments. The illuminance measurements in the apartments during the post-retrofit period show that the lighting levels at the points where the preretrofit measurements had been made, have not changed considerably. An important number of spaces are lit to higher levels than before. Most of the tenants consider the end
result brighter than the previous condition, with less glare problems. Table8includes the results of the illuminance measurements in the selected apartments of the Greek demonstration building during the nighttime, with the electric lighting on, before and after the retrofit.
5.5 Air quality The results of the indoor air quality measurements before the retrofit indicate in general acceptable indoor air quality conditions inside most of the apartments with some higher values recorded in several cases. After the retrofit the results are quite similar however the number of exceedances of the higher values seems to be reduced. More specifically: Regarding CO2 concentration, pre retrofit in the majority of the apartments, it exceeds the limit of 600ppm [34] for most of the time and the air quality is characterized as acceptable. In most apartments, the CO2 concentration exceeds the limit of 1000 ppm in the 16% of the values recorded. Post retrofit, the indoor air quality conditions in terms of CO2 concentration are quite similar, however the number of exceedances of the 1000ppm limit are significantly lower for all the apartments (ranging between 3 -11%of the values recorded). Outdoor CO2 concentrations are in the range of 300-400ppm for both cases. Concerning the VOCs concentration measured in the apartments, it was found that before the retrofit the highest percentage of occurrences fell in the comfort scale in the majority of the apartments. In several apartments the concentration values recorded were in the discomfort range with the possibility of more severe symptoms. After the retrofit, the results showed that in the majority of the apartments the concentration of VOCs is on comfort scale. In comparison with the pre-retrofit conditions it is obvious that the occurrences of VOCs concentration falling in the discomfort scale have significantly reduced. These results are probably due to better ventilation conditions and the information and training that the residents received on indoor air quality and ventilation. It should be noted that the classification of the concentrations of VOCs is based on the Molhave scale and its correlation with the outputs of the IAQ Kits as described in [35].
5.6 Evaluation of the innovative technologies This section describes the performance of the innovative technologies used in the Greek retrofitted building mainly the performance of the innovative energy efficient lighting system and the performance of cool and photocatalytic materials. a. The innovative energy efficient lighting system
The space where the lighting system was installed received no natural lighting before the retrofit, as there is no opening on the roof level, and was artificially lit by an incandescent lamp of 100W, located on the top of the stairs. Two indicative illuminance measurements were performed on the stairs between the seventh floor and the roof, before the retrofit, which showed that there was no daylight availability (Table9). Measurements during night time on the points shown in Figure 5Error! Reference source not found., were performed before the retrofit, with the incandescent lamp on.
Table 10 includes the results from the illuminance measurements on the stairs leading to the roof, after the retrofit. In order to check the pre-retrofit results again, the light pipe was covered with a non-transparent material. It is apparent that only the flight of stairs leading from the seventh floor to the landing area (point 4) receives some natural light from the window on the seventh floor. The rest of the stairs is dark, regardless the exterior conditions. On the contrary, the illuminance measurements after the retrofit, show that the light pipe system ensures high illuminance levels, on all steps and on the landing area at roof level. Even for low exterior illuminances (25klux) the illuminances are no lower than 90 lux, only with natural lighting. The daylight sensor that is installed in the system and controls the LED lamps is programmed to provide 50lux on point 6, i.e. close to the seventh floor level. Moreover, the sensor senses movement and turns the lamps off approximately 2 minutes after not perceiving any movement, in order to ensure energy savings and safety for the users. Measured data were used in combination with RELUX software to depict the lighting distribution in different operation conditions (natural lighting and artificial lighting) pre and post retrofit in the space where the energy efficient lighting system is installed. The results are shown in the following figures:
b. Cool and photocatalytic materials The following figure depicts the spectral reflectance of the samples tested in the laboratory using spectrophotometric techniques.
The spectral reflectance values were used for the calculation of the solar reflectance which is reported in Table 11. In the table the reflectance in the UV, VIS and NIR part of the solar spectrum are also reported. As it can be seen from the graphs but also from the tabulated values the ceramic tile presents a solar reflectance (58%) significantly higher that the asphalt membrane (13% ). This means that the post retrofit roof reflects larger amounts of solar radiation rather than absorbing thus staying cooler under hot summer conditions compared to the absorptive asphalt membrane. This was also verified through thermal imaging. The same applies for the plaster that presents high solar reflectance (71%). Moreover, the plaster will be able to maintain this solar reflectance due to the photocatalytic and selfcleaning properties.
It should be noted that for the plaster applied on the facades a light-colored shade was finally used (not white) in order to maintain the initial appearance of the facades for which a reference value of 0.5 has been considered.
5. Estimation of global energy savings and other performance indicators This section aims at providing a quantitative evaluation of the impact of the retrofit in terms of energy, environmental and financial performance. The validated models described in section 4.2 have been used for the estimation of different performance indicators using the same boundary conditions i.e. the same climatic data and the same user behavior for the pre and post retrofit cases, taking into account only the impact of the installed technologies and solutions. It is assumed that AC split units are used for both heating and cooling as the occupants of the building do not use the central heating system. The energy consumption (kWh/m2) for cooling, heating and domestic hot water, lighting, equipment, before (A) and after (B) the retrofit is shown in figure 17. Furthermore, Table 12 presents the annual energy consumption and CO2 emission data for the pre and post retrofit case.
The annual renewable electricity production from the PV system which has been installed in the SE façade is estimated to be 6573kWh (efficiency=0.13) if the heat losses of the inverter are considered. The reduction of the energy consumption for cooling is 84% and for heating 79%. Regarding lighting, the replacement of all conventional lighting (incandescent and compact fluorescent lamps) in the building with LED lamps has reduced significantly the
installed power for lighting. The analysis showed that this corresponds to a reduction in energy savings equal to 91% assuming that lights operate for 6 and 3 hours in heating and cooling period respectively. The annual energy presents a cumulative reduction of 81.6%. In this calculation the energy production of the implemented PV system has been taken into account. Furthermore, the global energy consumption (including heating, cooling, DHW, lighting) reaches 25.4 kWh/m2*year in primary energy. The conversion factor to primary energy for electricity is considered as 2.9 for Greece [36]. Finally, the reduction of CO2 emissions after the retrofit has been calculated. According to Greek standards, CO2 emissions are calculated by multiplying the energy consumption (kWh) with a constant, depending on the power source. For this case, the only power source that is taken into account is electricity. The corresponding constant for electricity is: 0.989 (kgCO2/kWh) [36]. The annual savings of CO2 emissions for the post-retrofit condition reach 81.6%. A separate analysis has been performed in order to evaluate the energy savings due to the use of the innovative energy efficient lighting system compared to the energy consumed by a 100Watt incandescent lamp, which was used before the retrofit. The monthly energy savings are approximately 5.4kWh (it is supposed that the artificial lighting is used for 3 hours each day for a 30-day month). According to [37] it was calculated that 20% more energy savings will be ensured by the daylight available, when both light sources (LEDs and daylight) are in operation, while another 10% can be saved by the occupancy sensor. Thus, it is assumed that the innovative lighting system will provide 70-80% energy savings compared to the lighting system used before the retrofit.
In order to evaluate the impact of the retrofit on thermal comfort, simulations were performed for the building under free floating conditions. It was found that there are strong differences in air temperature during the heating season between the pre retrofit condition compared to the post-retrofit one. Especially, the temperature increase of the post-retrofit condition, reaches 3.7°C on January, while the average temperature increase for the heating period is estimated at 3.1°C. In addition, an important increase in the minimum temperatures is estimated during winter reaching 5°C. During the cooling period, indoor temperatures present a reduction ranging between 0.5°C -1.5°C. Calculations of the PMV according to [38] indicate an improvement of indoor thermal comfort inside the apartments during both winter and summer after the retrofit as shown in Figure 18. For the heating season especially, the predominant value of PMV for the pre retrofit condition was around -
2 which characterizes the thermal perception as cold while for the post-retrofit condition the values of PMV are shifted towards -1 slightly cool to neutral resulting in improved comfort conditions. For the cooling season PMV values are shifted from the warm sensation area (+2) towards the slightly warm - neutral sensation area. It should be noted that the results regarding the global energy savings obtained from the validated simulations are consistent with the results estimated in the design phase from the holistic analysis indicating that the method provides accurate results and is appropriate for the determination of the optimum retrofit solutions. Moreover, the analysis has shown that the project targets as defined in section 3 have been met by the retrofit in terms of energy savings and energy savings for lighting, global energy consumption and reduction of CO2 emissions, indicating the success of the retrofit.
6. Cost effectiveness of the retrofit The socioeconomic analysis was performed for the retrofitted building according to the methodology explained in section 4.3. A payback period of 2.9 years was estimated for the retrofit compared with the payback of the investment on state-of-the-art energy efficient technologies that could be adopted rather than the innovative technologies. Furthermore, the analysis showed that the implemented retrofit solution is cost effective as saved energy costs (0.14EUR/kWh avoided) are lower than the average end-user energy cost in the baseline. Finally, it should be pointed out the cost of this retrofit project was approximately 100euros/m2 indicating that important energy savings and improvement in the environmental conditions can be achieved with a relatively low investment using the appropriate innovative and state of the art technologies.
7. Occupants evaluation The first part of the occupants’ evaluation had to do with their perception of their indoor environmental quality. Before the retrofit 69% of the tenants characterized the overall quality of their indoor environment (including thermal comfort, air quality, lighting and acoustics) as “bad”, while after the retrofit all the tenants declared that they are satisfied with the overall quality. More in detail, thermal comfort conditions in the apartments were characterized as cold during winter by 69% of the tenants before the retrofit and as warm/hot during summer by 88%. In addition, 69% of the tenants have reported significant drought problems in their apartments during winter. These replies reveal that the thermal
comfort conditions were not satisfactory. After the retrofit, 85% of the occupants characterized the indoor thermal comfort conditions as satisfactory and the rest as acceptable for both seasons. Most of the occupants stated that their thermal sensation is “neutral” during both winter and summer (14% found that during summer the thermal sensation is slightly warm). After the retrofit drought problems have been eliminated according to the occupants. This finding is in line with the air leakage measurement results. In addition, the mold/ condensation problems reported before the retrofit by 38% of the occupants were eliminated after the retrofit due to the envelope interventions. Natural lighting conditions inside the apartments were characterized as ‘bad” by 56% of the occupants before the retrofit, mainly due to glare problems faced in the rooms located in the unshaded SW facade of the building and due to the lack of natural light in the place where the energy efficient lighting system was installed. After the retrofit, the 86% of the occupants characterize the natural lighting conditions as neutral/satisfactory. Artificial lighting was found to be satisfactory by most of the occupants both before and after the retrofit however 14% of the occupants found the lighting levels to be brighter after the replacement of conventional lamps by LED lamps but not in a negative sense. Regarding indoor air quality, before the retrofit 31% of the occupants characterized the air quality in the apartment as “bad”. This is mainly due to internal sources of pollution (e.g. smoking inside the apartments, cleaning with chemical products etc.) and the lack of regular ventilation. After the retrofit, several occupants found their indoor air quality to be improved basically because of the natural ventilation strategies they were advised to follow by the University of Athens team. Regarding the retrofit satisfaction, it should be highlighted that all the occupants have declared their satisfaction. All the installed technologies and solutions have been positively rated by the occupants in terms of improving the indoor environmental quality and contributing to energy savings. Moreover, a specific question was asked to the tenants aiming to evaluate the performance of the energy efficient light pipe and all the tenants (100%) have confirmed that the technology has improved the lighting conditions in the installed space. Finally, the occupants have reported that after the retrofit they feel that their behavior has changed in terms of energy and environmental issues. More specifically, more than 90% of the occupants stated that they have used heating and cooling devices for fewer hours after the retrofit and this was also verified experimentally, and 71% declared that they prefer to use the ceiling fans over the AC. Many of the occupants (71%) declared that they are
interested in knowing their energy consumption (by looking in the installed smart meters monitors). It should be highlighted that the occupants’ perception about their indoor environmental quality is in line with the experimental and theoretical evaluation conducted for the building. This analysis indicates the significant success of the holistic retrofit of the 7-story apartment building and the acceptability and satisfaction of the occupants of their indoor environmental quality and the installed technologies and solutions.
8. Conclusions Retrofitting the existing poor quality residential building stock can significantly contribute to addressing the current global environmental challenges. There is a high potential in reducing the energy and carbon footprint of the building stock by promoting the energy efficient retrofit of buildings. This can be achieved with a cost effective investment if a holistic approach is used for the retrofit. This study has shown that a cost effective retrofit of multiple low income households using an optimum combination of innovative and state of the art technologies and solutions has been very effective in reducing energy consumption and carbon footprint and in improving indoor environmental conditions. More specifically, a low income multiple housing building has been retrofitted. The retrofit plan aiming to reduce the building’s energy and carbon footprint, improve the indoor environmental quality and be cost effective includes innovative as well as state of the art technologies and solutions and was determined following a holistic approach. In order to evaluate the impact of the retrofit, experimental monitoring activities have been performed before and after the retrofit. The experimental results show significant improvement of the building envelope and the thermal comfort conditions inside the apartments as well as reductions in the energy consumption. Furthermore, using advanced simulation techniques, total energy savings and other performance indicators have been estimated for the retrofitted building. The retrofitted building is found to consume 25.4 kWh/m2 y of electricity. The annual energy savings in the building and the reduction of CO2 emissions reach 81.6%. The energy saving for lighting reaches the value of 91%. The analysis of the occupant surveys showed a significant user acceptability of the retrofit and the installed technologies and solutions as well as significant improvement of indoor environmental conditions. The estimated the payback period of the retrofit was found to be 2.9 years compared with the payback of the investment on state-of-the-art energy efficient technologies that could be adopted rather than the innovative technologies implemented. Furthermore, the analysis showed that the
implemented retrofit solution is cost effective as saved energy costs (0.14EUR/kWh avoided) are lower than the average end-user energy cost in the baseline (pre retrofit) while the total cost of the retrofit was 100euros/m2.
Acknowledgements The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) in the framework of the “HERB project: Holistic energy-efficient retrofitting of residential buildings”, under grant agreement no 314283. We would also like to thank the University of Nottingham for performing the air leakage measurements with the novel pulse tester and providing the relevant results. Finally, we would like to thank Fibran and S&D Vlachos s.a. -Monotiki for donating the insulation materials installed on the building envelope.
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13. Paravantis, J. A., &Santamouris, M. (2016). An analysis of indoor temperature measurements in low-and very-low-income housing in Athens, Greece. Advances in Building Energy Research, 10 (1), 20-45. 14. Sakka, A., Santamouris, M., Livada, I., Nicol, F., & Wilson, M. (2012). On the thermal performance of low income housing during heat waves. EnergyandBuildings, 49, 6977. 15. European Foundation for the Improvement of Living and Working Conditions,First European Quality of Life Survey, European Foundation for the Improve-ment of Living and Working Conditions, Dublin, Ireland, 2003. 16. J.P. Clinch, J.D. Healy, Housing standards and excess winter mortality, Journalof Epidemiology and Community Health 54 (2000) 719–720. 17. D’Ippoliti, D., Michelozzi, P., Marino, C., de’Donato, F., Menne, B., Katsouyanni, K.,et al. (2010). The impact of heat waves on mortality in 9 European cities: Resultsfrom the EuroHEAT project. Environmental Health, 9, 37. 18. Baccini M1, Biggeri A, Accetta G, Kosatsky T, Katsouyanni K, Analitis A, Anderson HR, Bisanti L, D'Ippoliti D, Danova J, Forsberg B, Medina S, Paldy A, Rabczenko D, Schindler C, Michelozzi P., Heat effects on mortality in 15 European cities, Epidemiology. 2008 Sep;19(5):711-9. doi: 10.1097/EDE.0b013e318176bfcd. 19. Video on the Greek retrofit activities https://www.youtube.com/watch?v=Rw2UREIgOv8 20. HERB project website: http://www.euroretrofit.com/ 21. K. Giannopoulou, I. Livada, M. Santamouris, M. Saliari, M. Assimakopoulos, Y.G. Caouris, On the characteristics of the summer urban heat island in Athens, Greece, Sustainable Cities and Society, Volume 1, Issue 1, February 2011, Pages 16-28, ISSN 2210-6707, http://doi.org/10.1016/j.scs.2010.08.003. 22. EN13829(2001), Thermal performance of buildings. Determination of air permeability of buildings. Fan pressurization method,British Standards Institution 23. Vasilakopoulou, K., Kolokotsa, D., Santamouris, M., Kousis, I., Asproulias, H., Giannarakis, I., Αnalysis of the experimental performance of light pipes, Energy and Buildings (submitted) 24. E. Cooper, X. Zheng, M. Gillot, S. Riffat, Y. Zu (2014) A nozzle pulse pressurisation technique for measurement of building leakage at low pressure, 35th AIVC Conference " Ventilation and airtightness in transforming the building stock to high performance", Poznań, Poland, 24-25 September 2014
25. ASTM E903: Standard Test Method for Solar Absorptance, Reflectance, and Transmittance of Materials Using Integrating Spheres, ASTM International 26. ASTM E891-87(1992), Tables for Terrestrial Direct Normal Solar Spectral Irradiance Tables for Air Mass 1.5, ASTM International 27. ISO 22197-1(2007), Fine ceramics (advanced ceramics, advanced technical ceramics) -- Test method for air-purification performance of semiconducting photocatalytic materials -- Part 1: Removal of nitric oxide, International Organization for Standardization. 28. Fibran, IASA (2014), DICOM:Development of insulation cool materials based on XPS (09ΣΥΝ-32-1174), Deliverable 3.5: Experimental measurement results and sensitivity analysis (Available in Greek) 29. ASHRAE Guideline 14, (2002), Measurement of Energy and Demand Savings, American Society of Heating, Refrigeration and Air Conditioning Engineers, Atlanta, GA. 30. ISO 16346(2013), Energy performance of buildings – Assessment of overall energy performance, International Organization for Standardization, Switzerland, 2013 31. Eurostat (2016), Energy price statistics. Available on line at: http://ec.europa.eu/eurostat/statistics-explained/index.php/Energy_price_statistics 32. F.H. Rohles, S.A. Konz, B.W. Jones, (1983) Ceiling fans as extenders of the summercomfort envelope, ASHRAE Transactions 89 (1A) 245–263. 33. F.H. Rohles, S.A. Konz, B.W. Jones (1982), Enhancing thermal comfort with ceiling fans,Proceedings of the Human Factors Society 26th Annual Meeting 118–122. 34. CIBSE. Guide B (2005): Heating, Ventilating, Air Conditioning and Refrigeration. Guidance, London:The Chartered Institution of Building Services Engineers. 35. Assimakopoulos M. N., Giannopoulou K.,Asimakopoulos D., Wright D., Sheldon M. (2014), iSERVcmb IAQ Overall Summary Reports, Available on line at: http://www.iservcmb.info/sites/default/files/results/Indoor-Air-Quality/IAQtests/Public-report-Summaries-of-IAQ-tests.pdf 36. ΤΟΤΕΕ 20701-1 (2010), Technical Guideline of the Technical Chamber of Greece: Technical Guidelines on Buildings‟ Energy Performance, Technical Chamber of Greece, Athens, Grecce 37. EN 15193 (2007) Energy performance of buildings. Energy requirements for lighting, British Standards Institution
38. ISO 7730:2005, Ergonomics of the thermal environment -- Analytical determination and interpretation of thermal comfort using calculation of the PMV and PPD indices and local thermal comfort criteria, International Organization for Standardization, Switzerland, 2005
A
B
C
Figure 1: Front part of the building-NE Elevation(A,B) and rear part of the building-SW Elevation (C).
A B Figure 2: The proposed energy saving solutions (A)percentage of energy savings and CO2 emissions saved for all scenarios (B)
A
B
Figure 3: Images of the retrofitted building: Building envelope interventions (A), PV panels on the SE facade (B)
Figure 4: Images of positions of sensors installed in a representative apartment.
Figure 5: The measurement points on the stairs underneath the light pipe system
A
B
Figure 6: Thermal and visible images: missing thermal insulation (A), Air leaks from the window (B)
Figure 7: Thermal and visible images of the roof pre (left part) and post (right part) retrofit
15,5°C
14 AR01 12
10
8 7,5°C
A
B
Figure 8: Thermal and visible images of the building envelope (A) and windows (B) post retrofit.
Figure 9: Air leakage rates in three representative apartments pre and post retrofit
Figure 10: Energy signature for the building for the heating and cooling periods before and after the retrofit.
Figure 11: Monthly Energy consumption for a representative apartment for both pre and post retrofit conditions and its relative decrease.
Figure 12:Boxplots of the indoor and outdoor temperature of three representative apartments pre and post retrofit during February.
Figure 13:Boxplots of the indoor and outdoor temperature of three representative apartments pre and post retrofit during June.
Figure 14: Indoor temperature profile of a representative apartment pre and post retrofit (for January)
Figure 15: Lighting levels in the space where the energy efficient lighting system is installed pre and post retrofit
c. Figure 16:Measured values of spectral reflectance for the asphalt membrane (pre retrofit condition of the roof), the cool ceramic tile (post retrofit condition of the roof) and the photocatalytic plaster applied on the facades
Figure 17: Energy consumption per month for the pre (A) and post (B) retrofit condition
Figure 18: Diagram of frequency of appearance of PMV hourly values for heating (A) and cooling (B) seasons for pre and post-retrofit conditions for the representative.
Table 1: Envelope properties for the pre and post retrofit case. Construction
U value
Thickness
(W/m². K)
(mm)
Pre-retrofit Case
External wall
Materials (outer to inner)
gypsum plaster(20mm)-outer, brick(160mm), 1.900
200
0.284
300
Retrofit Case
gypsum plaster(20mm)-inner Mineral wool(rock wool 100mm)-outer, gypsum plaster(20mm), brick(160mm), gypsum plaster(20mm)-inner
Pre-retrofit Case
gypsum plaster(25mm)-outer, concrete(200mm), 2.450
Roof
250
Retrofit Case
gypsum plaster(25mm)-inner cement clay(20mm)outer, polystyrene
0.444
330
board(50mm), gypsum plaster(30mm), concrete(200mm), gypsum plaster(25mm)-inner
Pre-retrofit Case Internal walls
gypsum plaster(10mm)-outer, brick(130mm), 2.360
150
Retrofit Case
gypsum plaster(10mm)-outer, brick(130mm), 2.360
150
Pre-retrofit Case Floor
gypsum plaster(10mm)-inner
gypsum plaster(10mm)-inner concrete(130mm)-outer, mosaic( 20mm)-inner
4.182
150
4.182
150
Retrofit Case
concrete(130mm)-outer, mosaic( 20mm)-inner
Furthermore, the final layer of the roof insulation was a ceramic tile with cool material properties (i.e. high solar reflectance).
Table 2: Windows properties pre and post retrofit Opening
Pre-retrofit Case
Retrofit Case
Glazing type
Single
Double
Thickness
6 mm
13mm
Gas
None
Air filled
Frame type
Wood/Aluminium
Aluminium
Frame U - value
3.633 (W/m2.K)
3.476 (W/m2.K)
Glazing U - value
5.8 (W/m2.K)
2.7 (W/m2.K)
Table 3: Types and wattage of the lamps pre- and post-retrofit Lamp types
Watts of all lamps in the building
Pre-retrofit Case
Incadescent/ CFLs / LEDs
7789
Post-retrofit Case
LEDs
1520
Table 4: Solar photovoltaic panels characteristics Module dimensions
1655 x 989 x39 mm
Rated power
250 W
Efficiency
15.3%
No. of modules installed
40
Table 5: Innovative lighting system features Lighting type
Area lit (m2)
Pre-retrofit Case
Incadescent- 100 Watts
13.2
Post-retrofit Case
Daylight & LEDs- 40 Watts
Table 6: Overview of monitored parameters and corresponding instrumentation
Monitored
Method of Measurement / Instruments
Parameters Building Energy use
Energy Consumption
Smart meters &portal for remote access (Energy Management Modules by Ether)
Building Envelope &
Surface temperature
Infrared thermography (Dual View Thermal Imaging
Air tightness
& surface
Camera IR32 DS)
temperature distribution Air leakage rate/Air
Novel Pulse leakage tester/ Blower door test
Tightness Ventilation Rate
Tracer gas techniques (INNOVA 1312 Photoacoustic Multigas Monitor (LumaSense Technologies) connected to the INNOVA 1303 multipoint sampler and doser controlled by a PC on which the INNOVA7620 software is installed)
Building
Temperature
Environmental
Relative Humidity
Parameters
Black globe
Data loggers (TinyTag TGP-4500)
Black globe thermometer (Delta Ohm)
thermometer Air velocity
Airvelocity meter (Dantec 54N50 Low velocity flow analyser)
Concentration of
IAQ stations - F2000TSM-VOC-L series
VOCs& CO2 Illuminance
Digital illuminance meter (TES 1335)
Meteorological
Temperature
Meteorological Stations Data (National Observatory of
parameters
Relative Humidity
Athens)
Solar Radiation Wind Speed & Direction
Evaluation of
Solar Reflectance
Spectrophotometer (Carry 5000 by Varian)
innovative
Photocatalytic
Oxidation of NO to NO2 and ΝΟ3-
Technologies
Property Illuminance
digital illuminance meter (TES 1335)
Table 7: % discomfort hours for the pre and post retrofit case for a representative apartment % hours of discomfort Month
Pre retrofit
Post retrofit
Jan
83
76
Feb
76
33
Mar
70
15
Apr
24
0
May
21
7
Jun
71
79
Jul
87
99
Aug
91
98
Table 8:Pre and post retrofit Illuminance measurement data in various interior points in 2 selected apartments, during the night (artificial lighting) Interior Illuminance Measurements (lux)
Apartment 1
Pre retrofit
Apartment 2 Apartment 1 Apartment 2
Post retrofit
Living room
Kitchen
Bedroom 1
Bedroom 2
361
224
293
224
265
214
187
214
350
315
370
315
300
224
178
224
Table 8:Illuminance measurements on the stairs leading to the roof, before the retrofit Date/Time
Interior Illuminance Measurements (lux)
Exterior Illuminance (lux)
June/11:00
1.50
85,721
July/13:50
4
113,057
July/22:05
Point 1: 207
-
Point 2: 129 Point 3:97 Point 4: 22 Point 5:20 Point 6: 3 Table 9:Illuminance measurements on the stairs leading to the roof, after the retrofit LightingTechnology Date/ Time
Daytime measurements Overcast sky Daytime measurements Overcast sky
Nighttime measurements
Feb./ 13:00, light pipe uncovered Feb./13:15, light pipe covered March/12:30, light pipe uncovered March/12:30, light pipe covered March/22:45
Interior Illuminance measurements (lux)
Point 1- roof level 282.3
Point 2
Point 3
299.4
2.74
Exterior Illuminance measurements (lux) Point 5
Point 6
213.8
Point 4middle step 79.5
96.9
94.9
25,000
2.83
4.25
5.16
24.26
59.8
25,000
80
88.9
48.5
35.7
93.3
116.9
*23000
2.5
9.9
9.7
14.9
56.4
106.7
23000
22
103
121
45
89
67.4
-
Table 10:Illuminance Solar reflectance values for the tested samples Material
Solar
SRuv
SRvis
SRnir
reflectance
(300-
(400-
(700-
(300-2500nm)
400nm)
700nm)
2500nm)
Cool insulative ceramic tile
58
17
51
65
Bituminous membrane (sample from the
13
5
16
16
71
4
77
70
market) Photocatalytic plaster
Table 11: Annual energy consumption and CO2 emissions pre and post retrofit and the related % reduction Pre retrofit
Post retrofit
energy consumption (kWh/y)
85711.2
15739.1
energy consumption (kWh/m2/y)
110
20
energy consumption in primary energy (kWh/y)
248562
45643
CO2 emissions (kg/y)
245828
45141
% Reduction
81.6
