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Evaluation of a sample building with different type building elements in an energetic and environmental perspective
Renewable and Sustainable Energy Reviews 115 (2019) 109386
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Evaluation of a sample building with different type building elements in an energetic and environmental perspective
T
C. Ozalp∗, D.B. Saydam, K.N. Çerçi, E. Hürdoğan, H. Moran Department of Energy System Engineering, Faculty of Engineering, Osmaniye Korkut Ata University, Osmaniye, Turkey
ARTICLE INFO
ABSTRACT
Keywords: Energy efficiency Environment Numerical analyses Thermal insulation TS 825
The energy demand for heating in buildings in a residential area depends on the weather conditions of the area, the architectural characteristics and thermal-physical characteristics of the buildings, as well as the number of buildings in the settlement and the population of the settlement, accordingly. This study aimed to numerically determine the heat losses that may occur in case of different building materials (bricks, pumice, aerated concrete and briquettes) and insulation materials (XPS, EPS, rockwool and glass wool) used in the design of buildings, by applying the Finite Element Method (FEM) and considering the outdoor and indoor weather conditions proposed in Turkish Thermal Insulation Standard (TS 825). Then, the heating requirement according to the TS 825, the monthly fuel consumption, the payback period and the emission amounts in case of insulation were calculated for a model building with an external wall made of different building materials. In this study, the conditions of a model building located in Kahramanmaraş/Turkey were discussed separately in terms of being thermally insulated and non-insulated. As a result of the analyses obtained by using FEM, the effect of the wall building material on heat losses was found to be much higher than that of insulation material. Following the application of thermal insulation to the non-insulated building model, it was seen that the payback period of the first investment value required for the insulation application varied between 0.25 and 1.74 years depending on the type of fuel used for the heating energy requirement as well as on the type of building material. In the case of using briquette wall in the building, it seemed that the heating requirements, monthly fuel consumption and emission amounts were higher than those with other building materials. The briquette wall was followed by bricks, pumice and aerated concrete, respectively.
1. Introduction The industrial revolution has brought out urbanization and industrialization as a dominant outcome of economic and social modernization. Accordingly, the world's population growth and the energy demand that emerged with the impact of industrialization continues to increase with each passing day. The growing energy demand, in particular, has increased the use of fossil fuels (oil, natural gas, coal, fuel oil, etc.), which leads to increased CO2 and other greenhouse gas emissions [1]. As it is known that the world will run out of fossil fuels as an energy resource in the future, there have been efforts to make the efficient use of energy through legal regulations, both in Turkey and in the world. Particularly in buildings, certain levels of economic benefits can be achieved by energy efficiency measures and in like manner, harmful environmental factors can be reduced by diminishing the energy consumption [2]. With the purposes of reducing the energy consumption and
∗
preventing the use of conventional fuels causing greenhouse effect and further increase in CO2 emissions, extensive research on energy efficiency and energy conservation in buildings has been carried out in Turkey, where the significant amount of energy demand is imported [3] and fossil fuels are used in the power plants-especially in coal-fired power plants with low efficiency [4]. It is of great necessity to minimize the energy requirement for heating and cooling of buildings, to reduce the amount of energy consumed for illumination without compromising on comfort conditions, to minimize the amount of energy as much as possible and to take measures accordingly to provide energy conservation. One of the easy and efficient ways of preventing energy loss in buildings is the thermal insulation in buildings. The main purpose of placing the insulation material on the building envelope is to reduce the energy consumption for heating or cooling by increasing the thermal resistance of the building envelope [5]. One of the most important functions expected from the buildings is that they should provide suitable comfort conditions. Furthermore, one
Corresponding author. Tel.: +90 328 8271000x3502; Fax: +90 328 8250097. E-mail address: [email protected] (C. Ozalp).
https://doi.org/10.1016/j.rser.2019.109386 Received 19 March 2019; Received in revised form 5 August 2019; Accepted 8 September 2019 1364-0321/ © 2019 Elsevier Ltd. All rights reserved.
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of the most important parameters to be considered when examining the energy efficiency and energy inputs of a building is the thermal comfort of the residents. The comfort assessment of the residents is made using thermal comfort standards. These standards have a significant impact on evaluating the energy performance of buildings, and accordingly, on the energy consumption of buildings [6]. The standard for thermal insulation rules in buildings in Turkey are TS 825 (Turkish Thermal Insulation Standard) [7]. This standard aims to save energy by limiting energy consumption in the heating of buildings in Turkey, which forms an important part of the energy used. In the context of TS 825, Turkey is divided into four degree-day zones according to the climatic conditions of the cities from the hottest to the coldest. According to the calculation method of TS 825, the whole building is taken into consideration and the heat losses that may be caused by the floor, ceiling and exterior walls of the building are calculated. This standard aims to determine the annual heating energy requirement for buildings by taking into account the outdoor and indoor temperature values. In the method followed, heat loss and heat gain (solar energy, etc.) is calculated over monthly average meteorological values, and the annual heating energy requirement is specified by subtracting heat gains from heat losses. In the literature, it is possible to see many studies about thermal insulation applications in houses, determination of insulation thickness in thermal insulation, energy efficiency in buildings, energy and environmental problems originating from housing sector. In the literature, it is possible to see many studies about thermal insulation applications due to heat losses in houses, determination of insulation thickness in thermal insulation applications, energy efficiency in buildings, energy and environmental problems caused by housing sector [8–26]. Özkan and Onan [9], in their study, examined the effect of the windows and the wall area on the heating energy requirement of the building and the optimum insulation thickness by P1–P2 numerical calculation method. Moreover, they examined the changes in the variety of insulation materials, glass surfaces and fuel types as well as the optimum insulation thickness in four degree-day regions of Turkey in addition to the effect of the results on CO2 and SO2 emissions. As a result of the study, in the building which was constructed with extruded polystyrene foam (XPS) insulation material, in which natural gas and fuel oil was used as fuel and the ratio of the glass area to the external wall area was 0.2%, the energy savings were found as 13.996, 31.680, 46.613 and 63.071 $/m2, respectively and the payback period of the investment was 2.023, 1.836, 1.498 and 1.346 years in the four regions, respectively. In the event that XPS was used as the insulation material and natural gas as fuel, CO2 emissions were observed to decrease by 50.91%. In addition, CO2 and SO2 emissions decreased by 54.67% when XPS was used as insulation material and fuel oil as fuel. Romania et al. [26] conducted studies on buildings that account for the majority of energy consumption in Morocco. The authors studied the optimization of the building envelope to avoid high energy consumption of buildings and used the general regression approach for dynamic simulation. At the end of the study, the methodology revealed that the low energy buildings in Morocco could be successfully used for the optimization of the building envelope. Kazanasmaz et al. [27] aimed to determine the energy performance of the residences in İzmir, based on the relationship between energy performance and residential architecture. The authors focused on the energy consumption for heating purposes in the context of the Energy Efficiency Law [28], the Energy Performance Regulation in Buildings [29] and Standards Assessment Methods Related to Energy Quality of Housing (PEP-SDM), which are in force in Turkey. In the study, the energy performance evaluation method was conducted based on the Turkish standard TS 825 and the European standard EN ISO 13790. In the light of the regulations, the authors also determined that this study would help to estimate the energy performance of the buildings at the first design stage. In a study by Doymacı [30], the author identified all long-term daily temperatures taken from meteorological stations for all the provinces in Turkey and locations of heating degree days and cooling degree days of different provinces. In a
Fig. 1. Schematic view of the modelled wall; (1) internal plaster, (2) building material, (3) thermal insulation material, (4) external plaster.
study conducted by Dilmaç and Kesen [31], the writers compared TS 825, determined as the standards of thermal insulation in Turkey, with IS0 9164 and EN 832, as well as with the German standards. It was stated that each method had the same equations, the same constraints and the same flexibility. It was shown that the formulas used in the calculation of heating energy requirements were almost the same as those used in ISO 9164. However, in the German standard, the heating time in the whole country is accepted as a fixed value of 3500 K-days per year. In TS 825, it is known that there is a different heating day zone for each region. In addition, it is stated in ISO 9164 that it is impossible to perform calculations manually for Qmount, which refers to the outdoor temperature i.e. the daily average temperature and the monthly heating requirement. The study, however, showed that such calculations could be done manually for TS 825. On the other hand, EN 832 allows the calculation period to be selected as months or seasons, and the DD method to be uses. This shows that the procedures performed for all three methods are similar. Guattari et al. [32] used the FEM model to remanufacture a measuring device by using a 2D model measurement device instead of 1D in measuring the thermal resistance of the wall, and by including the internal heat sources into measurement. The main purpose of the study is to minimize the effect of internal heat sources to compare the thermal resistance of wall models with different heat resistance, and thus to obtain the best heat flow position. They compared this with a FEM model corresponding to the preliminary experimental results of the study. Bolattürk [33], calculated the optimum insulation thickness, energy savings and payback period by selecting cities from four different climatic regions of Turkey. The annual heating requirement of buildings in different climatic zones was determined by the degree-day method. The researchers first calculated the amount of heat loss through the exterior walls so as to calculate the optimum insulation thickness to be used on the exterior 2
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Fig. 2. Wall models and dimensions used in the calculations: (a) brick, (b) pumice, (c) aerated concrete. Table 1 Technical specifications of building materials [7]. Building Material
Thickness (m)
k (W/mK)
R (m2K/W)
Internal plastering External plastering Brick Pumice Aerated concrete Briquette
0.02 0.02 0.13 0.15 0.15 0.10
0.87 0.87 0.45 0.18 0.11 0.63
0.023 0.023 0.28 0.83 1.36 0.15
Table 2 Technical specifications of thermal insulation materials [40]. Thermal Insulation Material
k (W/mK)
Cost (TLa/m3)
Rockwool Glass wool EPS XPS
0.040 0.040 0.039 0.031
180 130 240 350
a
Exchange rate (selling): 1 Turkish Lira (TL) = 6.46 USD ($) announced at 3:30 p.m. on 7 September 2018 by the Central Bank of Turkey.
walls. In these calculations, the convection resistance of the internal and external environment and the transmission resistances of the wall and the insulating material were taken into consideration in order to determine the total heat transfer coefficient. Then, they determined the optimum insulation thickness for the exterior walls according to the life cycle cost analysis calculation method. In this study, five different types of fuel and a single insulation material were specified. It has been shown that the optimum insulation thickness varied between 2 and 17 cm, energy savings could be achieved between 22% and 79%, and the payback periods were between 1.3 and 4.5 years depending on the climate characteristics of the selected city and the type of fuel used. Ekici et al. [34], estimated the optimum insulation thickness, energy savings and payback periods by selecting four cities in different climate zones determined by Turkish Thermal Insulation Standard (TS 825). With the purpose of examining the heat losses, the researchers studied stone, brick and concrete building materials mostly used in practice for wall building in Turkey. They made calculations using four different
Fig. 3. Dimensions of the wall models used in the study.
thermal insulation materials and five types of fuel. During the calculations, first, the heat losses in the walls, which constitute a large part of the heat loss, were calculated by considering all the convection and transmission resistances between the internal and external environments surrounding the wall. Then, the writers determined the thermal insulation thickness for the walls according to the annual energy cost calculation method. As a result, the optimum insulation thickness ranged from 0.2 cm to 18.6 cm. Heat loss and optimum insulation thickness were observed when the concrete wall was used the most. It was also seen that energy savings ranged from $ 0.038/m2 to $ 250.415/m2, and payback times ranged from 0.714 to 9.104 years, depending on the city, the fuel and building materials used. Bellamy 2014 [35], in a study by Bellamy, the writer aimed to determine the effect of dynamic and equivalent U factors that can predict the relative energy performance of various wall designs in different climates. In this
Table 3 Properties of fuels chosen for using in estimations [29,41]. Fuel
Lower Heating Value (Hu)
Cost
CO2 Emission Conversion Factor FSEG (kg eq. CO2/kWh)
Combustion Efficiency η (%)
Natural Gas Coal (Imported) Fuel-Oil No:4
34.526 × 106 J/m3 29.295 × 106 J/kg 41.326 × 106 J/kg
1.119 TL/m3 1.190 TL/kg 3.100 TL/kg
0.234 0.433 0.330
90 66 80
3
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• Increase the amount of energy saving by considering the effect of •
building materials in houses and thus contribute to energy efficiency. Reduce the amount of fuel used for heating by diminishing the heat loss in the houses and reduce the carbon emissions of buildings.
In line with these objectives, it is aimed to present this study as a unique example of scientific research or engineering and architecture practices to be applied within the scope of energy efficiency in buildings. 2. Material and methods Thermal insulation is an effective element in reducing the heating and cooling loads to a minimum level by changing the thermo physical properties of the building envelope. Insulation is a practical and rational solution that plays an important role in energy saving [34]. It was stated that 25–40% of heat loss might occur through the walls of a building without thermal insulation, 23–27% through the roof, 9–10% through the windows, 13–15% from the ground, and 16–19% through infiltration (leakage) [36]. This study will examine the external walls of buildings with and without thermal insulation by considering the buildings constructed with different wall building materials widely used in Turkey in the past and those materials that have started to be used in recent years. Fig. 1 shows a schematic diagram of the wall model used in the calculations. In the study, four different building materials such as brick, pumice, aerated concrete and briquette were chosen for the external wall model on which thermal insulation would be applied. The choice of building materials and insulation materials was made by taking into account the thickness of the material, the average outside temperature of the region, thermal conductivity coefficient and price [37]. In recent years, there have been many improved insulation materials which have superior thermal insulation properties due to their low thermal conductivity [38]. Fig. 2 shows the schematic view of the wall models formed with different building materials and Table 1 gives the technical properties of the building materials which form the wall model. Table 2 shows the technical characteristics of the four different insulation materials discussed in the analysis [39]. Fuel costs and emissions for different fuels have also been evaluated in the study. Table 3 provides the technical specifications of the different fuels for which the evaluation is made. For numerical analysis using FEM, the governing equation involves heat transfer in solids [32]. It is given in Equation (1).
Fig. 4. The geometry of the wall models (a) and the structure of the mesh (b).
study, since these U factors are the parameters explaining the effects of heat mass, solar heat gain and insulation on the heat conduction through the building envelope, the importance of the effects of these parameters are emphasized. In this context, a simulation analysis was performed in eight cities to determine the energy performance of different wall designs and to determine the dynamic and equivalent Ufactors of these walls. The results show that there is a strong correlation between wall energy performance and the equivalent U factor, except for the coldest climatic zone. It is clear that this equivalent U factor can be considered as an indicator of wall energy performance for global housing. This study first analyzed numerically the heat losses which might occur when different insulation materials (XPS, EPS, rockwool and glass wool) were applied on various building materials (brick, pumice, aerated concrete and briquettes) used in a building model design by using Finite Elements Method (FEM). Then, the heating requirement, monthly fuel consumption, and payback period in case of insulation and the amount of emissions were examined for a sample building where external walls of different materials were used. This study has aimed to:
• Select the building and insulation materials well during the initial design stage of the houses and reduce the heat loss caused by building materials.
Fig. 5. Distribution of provinces according to the degree-day zones in TS 825 [7]. 4
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Fig. 6. Architectural drawings of the south facade (a), north facade (b), east/west facade (c), and the top view (d) of the building model used in the calculations.
cp
T + t
q= Q
the 2nd degree day zone in TS 825 were applied. According to this, indoor and outdoor temperatures were accepted as 19 °C and 13.6 °C respectively, and the heat transfer coefficient values of indoor and outdoor environment were taken as 7.7 W/m2K and 25 W/m2K respectively. Adiabatic boundary conditions (heat flux neglect at boundaries) were applied to the lower and upper boundaries of the wall. The thermal properties of the wall building materials were selected as indicated in Table 1 [7]. For numerical analysis using FEM, the dimensions of all walls were considered the same (Fig. 3). COMSOL Multiphysics Package Program was used for numerical analysis based on FEM method. Fig. 4 shows the geometry of the wall models and the mesh structure. The mesh structures of the wall models are triangular and consist of 892 elements. Turkey is divided into four main zones based on the number of degree-days (DG) according to TS 825 [7,38,42–44]. Fig. 5 shows the distribution of these zones on the map of Turkey. The calculations were carried out in the province of Kahramanmaras, which is within the 2nd
(1)
Here, ρ is the material density (kg//m3), cp is the specific heat capacity (J/kgK) at constant pressure, and Q is the heat source (J). Fourier law is used for the transmission of heat:
q=
k
(2)
T
Here, k is the thermal conductivity coefficient (W/mK), T is the temperature gradient (K), and q is the heat flux (W/m2). In order to perform heat transfer analyses at the boundaries of the structure, convection boundary conditions were applied to internal and external surfaces. Here, Newton's cooling law (equation (3)) was used.
q= h (Td s
(3)
T) 2
Here, h is the heat transfer coefficient (W/m K), Tout is the outdoor temperature (K), and T is the surface temperature (K). For the boundary conditions, the conditions specified according to 5
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Fig. 7. Temperature contour graphs in case of application of rockwool and glass wool as insulation materials in different types of wall models; (a) brick, (b) pumice, (c) aerated concrete, (d) briquette.
degree-day zone, located at latitude of 37.5° and a longitude of 36.9°, and at an altitude of 568 m. Fig. 6 shows the architectural drawings of the building model used in the calculations. The sample building had 250 m2 of floor space, 320 m2 of ceiling as well as 5 floors including the ground floor, with a 2.80 m of monolayer component between each floor. The annual heating energy requirement of the sample building was calculated according to whether the building was thermally insulated or non-insulated. In the calculations made for an insulated building, the external wall, floor and ceiling insulation thickness were taken as 4 cm, 5 cm and 5 cm respectively, taking into account the calculation method given in TS 825. Since all of the balcony doors were covered with glass at the time of the calculations, they were all included in the window area. The building chosen for this study has single-layer building materials. Additionally, it is assumed that the exterior surface of the building where the thermal insulation is applied is not connected to any building element since the building is detached. Building calculations were made
by ignoring a thermal bridge. The specific heat loss (H) of the building would have increased if the building had a thermal bridge. With the increase in the heat loss in the building, the annual heating requirement of the building would have increased in the same proportion. However, the thermal insulation thickness was determined within the scope of the conditions specified in TS-825 and it was assumed that insulation was applied to the outer shell of the whole building (including reinforced concrete elements that may form thermal bridges such as balconies, beams, columns and fasteners). In the light of these assumptions, it is expected that the effect of thermal bridge-induced heat loss will be very low. It is stated in the literature that thermal insulation applications will eliminate the formation of a thermal bridge [45–47], and in this study, it has been assumed that a good thermal insulation was applied to the whole outer shell of the building and thus, the formation of a thermal bridge was ignored. Also, it was assumed that there were no thermal bridges in the building. In addition, the soil contacting surface and the under-roof surface were adopted as standard for each zone. In 6
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Fig. 8. Temperature contour graphs in the case of applying EPS as insulation material in different types of wall models; (a) brick, (b) pumice, (c) aerated concrete, (d) briquette.
the study, only the heating load was calculated, but the calculation of condensation and cooling load were not included. Internal gains in the sample building were taken in accordance with TS 825. When calculating solar energy gains, the glasses were selected as standard double glazing. It was assumed that the building was under the influence of shadows like trees and within the building class of up to ten-storey buildings. In order to calculate the amount of energy consumed annually in the building model, it was necessary to determine the heat losses through the external walls of the building according to TS 825. Below are the equations used in the heat loss calculations.
Qy =
Qm
Qm = [H (
i
monthly average internal gains (W), s,m to monthly average external gains (W), t time (s). The specific heat loss in the building (H, W/K) is sum ofthe heat loss by means of conduction and convection (HT), and the heat loss through ventilation (Hv) [7]:
(4) e)
m ( i, m
+
s, m )].
t
H = HT + HV
(6)
HT =
AU + IUI
(7)
HV = . c. V I = 0,33. nh . Vh
(8)
An = 0,32. Vgross
(9)
U=
(5)
Here, Q y refers to the annual heating energy requirement (J), Q m to the monthly heating requirement (J), i monthly average internal temperature (°C), e monthly average outdoor temperature (°C), m to the monthly average use factor for gains (no units), i,m refers to the
R=
1 Ri + R + R e
(10)
d (11)
h 2
In the equations, A is the area of the building elements (m ) and U is the thermal conductivity coefficient of the building elements. It was 7
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Fig. 9. Temperature contour graphs in the case of applying XPS as insulating material in different types of wall models; (a) brick, (b) pumice, (c) aerated concrete, (d) briquette.
assumed that the building elements were designed in such a way that they would not condensate and no thermal bridges would form, and the inter-storey reinforced concrete was insulated in such a way that R resistance would be 0.8 as specified in TS 825. The “U” values of the building elements were determined using equation (10) according to the calculation method specified in the standard. Monthly internal gains in the building were calculated by using equation (12): s, m
=
ri, m xgi, m x Ii, m x Ai
m
GLRm = (
e(
(14)
1/ GLRm)
i,m
+
s,m)/H( i,m
e,m )
(15)
In the equations, Fw refers to the correction factor for the glasses (taken as 0.8 in calculations), g refers to the solar energy factor for the perpendicular surface (taken as 0.75 in calculations), and GLRm refers to the monthly average gain utilization factor. In the case that the GLRm value, which is a parameter of monthly heating requirement calculations, exceeds 2.5, it is accepted that there is no heat loss for that month. The months in which the GLRm is higher than 2.5 correspond to the summer months with hot climatic conditions where there is no need for heating. In the calculations, the heating requirement has a negative (−) value for the months in which the GLRm is higher than 2.5, and in the case that these values are included in the annual heating energy requirement, the results will be inaccurate. The TS 825 method carries out the process steps in order to avoid the miscalculation of the annual heating requirement, taking into account only the months when heating is required [7,31].
(12)
Here ri, m is the monthly average shading factor of transparent surfaces with the building storey height (m), and gi, m is the solar energy transmission factor. In calculations, ri, m was taken as 0.6 according to TS 825. The solar energy transmission factor was calculated by using equation (13) for the case where multi-layer glass was used, whereas the monthly average gain utilization factor was calculated with the following equation No.15.
gi, m = Fw . g
=1
(13) 8
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Fig. 10. The amount of heat transfer through the wall in the unit area per unit of time (heat flux) according to different wall and building materials.
Fig. 11. Variation of surface temperature of the inner wall according to different wall and building materials.
The feasibility of the thermal insulation was evaluated by considering the payback period (PP, year). The payback period is determined by the following equation.
C PP = ti NE
following equations according to the total energy consumption of the building and the type of fuel used [48].
SEGMy = By x Hu x FSEG
(16)
By =
In the equation, Cti, refers to the first investment cost required for thermal insulation (TL) and NE refers to the annual savings amount (TL/year) [41,49,50]. The amount of annual CO2 emissions was determined by using the
(17)
Q year Hu
k
(18)
Here, SEGMy refers to the annual amount of CO2 emission (kg equivalent CO2), Hu refers to lower heating value of the fuel (kJ/m3 or kJ/kg), By refers to the annual amount of fuel (m3 or kg), and FSEG 9
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Fig. 12. Distribution of temperature across the wall where different thermal insulation materials are applied to the same building materials; (a) brick, (b) pumice, (c) aerated concrete, (d) briquette.
refers to CO2 emission conversion coefficient according to the type of fuel (kg equivalent CO2/kWh) (Table 3), Hu indicates the lower heating value of the fuel, and the ηk indicates the combustion efficiency [29].
observed in the wall model where aerated concrete building material was used, while the highest heat loss was observed in the wall model where briquettes were used. The amounts of heat transfer (heat flux) values through the external wall in the unit area were calculated with the FEM method according to different wall and building materials per unit time (Fig. 10). As can be seen from Fig. 10, the least heat loss was in the wall model with aerated concrete building material (1.882 W//m2) and the most heat loss was in the wall model with briquette building material (3.714 W/m2). When the walls were compared with respect to the insulation materials, the least heat loss was seen when XPS insulation material was used and the most heat loss occurred in the cases where rockwool and glass wool insulation materials were used. Fig. 11 shows the change in surface temperatures of the inner wall, which was calculated numerically by FEM method according to different wall and building materials. The highest inner surface temperature values were achieved in the buildings with the aerated concrete, which causes the lowest heat loss. Likewise, the highest wall surface temperatures were obtained in the buildings where XPS insulation material was used, causing the least amount of heat loss. It was determined that the reason for this situation was due to the thermal properties of the wall building and insulation materials. While the wall temperature was higher in walls with building and insulation materials having a low heat conduction coefficient due to less amount of heat loss, the wall models with building and insulation materials having a high heat conduction coefficient had a lot of heat loss, as a result of which inner wall temperature can remain at lower values. Fig. 12 demonstrates the temperature distribution values obtained
3. Results and discussions In the study, firstly the heat losses that can occur in the application of different insulation materials (XPS, EPS, rockwool and glass wool) to building materials (brick, pumice, aerated concrete and briquettes) used in the design of the building model were calculated numerically using Finite Element Method and the results were evaluated. Fig. 7 shows the temperature contour distribution when rockwool and glass wool (the same thermal conductivity values, different places of use) were used as the insulation material for different wall building materials. When the temperature contour distributions are examined, it is observed that the most heat loss is in the wall model with briquette building material. It is also clear that the least heat loss is in the wall model with aerated concrete building material. Fig. 8 shows the distribution of the temperature in the contour plot in the case of the application of EPS material as insulation material to the different wall building materials. The contour graphs showed that the wall model with briquette building material had the most heat loss, whereas the least heat loss was in the wall model with aerated concrete building material. Fig. 9 shows the temperature distributions in the case of applying XPS material as insulation material to the different wall building materials in the contour plot. Similar results were obtained in this study as were found for the other insulation materials. The lowest heat loss was 10
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Fig. 13. Distribution of temperature values obtained across the wall when the same thermal insulation materials are applied to different building materials; (a) Rockwool, (b) Glass wool, (c) EPS, (d) XPS.
the briquette wall building materials were used. Furthermore, it is seen that the effect of wall building materials on heat loss was more than that of insulation materials. In the next section of the study, heating loads were calculated according to the external wall where four different building materials (brick, pumice, aerated concrete and briquette) were used for a sample building, based on which the amounts of monthly fuel consumption and emission were determined. The calculations were done separately according to whether or not the building was insulated, and the results were compared. The calculations made for the insulated building were carried out for a single insulation material by taking into account the FEM results. Considering the flammability class and heat conduction coefficient of the external wall structure of the building, rock wool was used and applied on different wall models. In addition, glass wool was used in the roof covering and XPS was used on the floor. Fig. 14 shows the graphs of comparing the monthly heating requirement of the building model with different building elements for thermally insulated or non-insulated cases. When the heating load of the building was examined, due to the high heat transfer coefficient of the wall structure formed from the briquette building material, the heat losses had the highest values among all the cases where other building materials were used. Following the briquette wall, the heating requirement are sorted from large to small as brick wall, pumice wall and aerated concrete wall, respectively. The graphs also demonstrate that there is a decrease in the heating requirement due to the application of thermal insulation. After determining the monthly heating requirements for the sample building, it was investigated at which costs these requirements could be met with different fuels. Figs. 15–17 demonstrate the costs incurring from meeting the heating requirements with natural gas, coal and fuel
Table 4 Payback period of the investment in the case of thermal insulation to thermally non-insulated wall models. Payback Period (year) Fuel Type
Brick Wall
Briquette Wall
Pumice Wall
Aerated Concrete Wall
Natural Gas Coal Fuel-oil
0.63 0.58 1.30
0.85 0.77 1.74
0.34 0.31 0.70
0.27 0.25 0.55
along the wall when different thermal insulation materials are applied to the same building materials. As can be seen from the figure, except for XPS, the temperature distributions of the other insulation materials are similar across the wall because their thermal conductivity coefficient values are close to each other. Fig. 13 and Table 4 demonstrates the distribution of temperature values obtained across the wall when the same thermal insulation materials were applied to different building materials. It is clear from the figure that the wall construction material is of great importance in insulation applications. The temperature difference between the inner surface and the external surface of the aerated concrete wall material, which had the lowest thermal conductivity, was highest. In this way, it was the wall building material that kept the interior environment at the highest value of the walls studied. Second was pumice concrete. However, it was found that the temperature difference between the inner surface and the external surface of the briquette wall was lower in the briquette wall building material than that of other wall building materials. This shows that the heat loss was mostly in the structures where 11
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Fig. 14. Comparison of the monthly heating requirement of the building model with different building elements for thermally insulated and non-insulated cases. a) Brick Wall b) Pumice Wall c) Aerated Concrete Wall d) Briquette Wall.
Fig. 15. Monthly fuel consumption of thermally insulated and non-insulated wall model consisting of different building elements when natural gas is used for heating. a) Briquette Wall b) Pumice Wall c) Aerated Concrete Wall d) Brick Wall.
oil, respectively in the case that different building materials were used, in relation to whether or not the building was insulated. As seen from the figures, the insulation of the building led to a significant decrease in the costs. In addition, the highest cost for all types of fuel appeared when the briquette material was used due to its heat transfer coefficient. The briquette wall was followed by brick, pumice and aerated concrete wall models. The payback period was taken into consideration in evaluating the insulation in terms of cost wise. Table 4 gives data for the payback periods (PP) estimated as a result of thermal insulation to the building when different building materials and different fuels were used. As seen from the table, PP values vary between 0.25 and 1.74 years depending
on the building material and fuel. In the sample building, the fuel consumption required to meet the monthly heating requirement was calculated and the CO2 (kg) equivalent of these fuel consumptions was determined. Figs. 18–20 demonstrate the CO2 (kg) equivalent values when the heating requirements were met with natural gas, coal and fuel oil, respectively in the case that different building materials were used, in relation to whether or not the building was insulated. As seen in Figs. 15–17, the insulation of the building reduced fuel consumption, thus resulting in a significant decrease in the amount of equivalent CO2. As a result of the combustion of the carbon molecules in the chemical structure of the coal, it releases many harmful wastes to the environment and the most 12
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Fig. 16. Monthly fuel consumption of thermally insulated and non-insulated wall model consisting of different building elements when coal is used for heating. a) Brick Wall b) Pumice Wall c) Aerated concrete Wall d) Briquette Wall.
Fig. 17. Monthly fuel consumption of thermally insulated and non-insulated wall model consisting of different building elements when fuel-oil is used for heating. a) Brick Wall b) Pumice Wall c) Aerated concrete Wall d) Briquette Wall.
important of these is CO2. As a result of calculations, it was found that coal had the highest emission value. Coal was followed by fuel oil and natural gas. Due to its chemical properties, natural gas does not contain much pollutant material compared to other fuels. The calculations revealed that natural gas had lower values than other fuels in terms of emissions. The figure also showed the maximum amount of CO2 equivalent for all fuel types emerging when the briquette material was used due to its heat conduction coefficient. The briquette wall was followed by brick, pumice and aerated concrete wall models.
sample building with different wall structures was calculated according to TS 825 during the heating season, in relation to whether or not the building was thermally insulated. The fuel consumption and the CO2 (kg) equivalent based emissions, which correspond to the heating requirements calculated according to the different building materials, were determined, and the sample building, energy cost and environmental aspects were examined. The results obtained from the study are given below: ➢ The heat loss calculations were performed numerically first by using Finite Elements Method and then the obtained results were compared by considering the different building and insulation materials. As a result of the numerical analysis, it was determined that the wall
4. Conclusions In this study, the heating energy requirement (heating load) for a 13
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Fig. 18. The amount of CO2 equivalent of the building with different wall types in which natural gas is used for heating. a) Brick Wall b) Pumice Wall c) Aerated Concrete Wall d) Briquette Wall.
Fig. 19. The amount of CO2 equivalent of the building with different wall types, in which coal is used for heating. a) Brick Wall b) Pumice Wall c) Aerated Concrete Wall d) Briquette Wall.
building material had a more effective role in reducing the heat losses than the insulation material. ➢ As a result of the calculations made for different wall building materials, the values in the building with the briquette wall model were higher than those of other building materials in terms of heating requirement and monthly fuel consumption. The building with a briquette wall was followed by the brick wall, pumice wall and the aerated concrete wall, respectively. It is necessary to analyse the building well at the initial design stage and select the building material accordingly in order to increase the amount of energy savings from the houses.
➢ In the scope of the study, the use of different building materials was also evaluated from an environmental point of view. Although the amount of emissions (kg equivalent CO2) varied according to the type of building material, the least amount was observed in natural gas compared to other fuels. Natural gas was followed by fuel oil and coal. For existing buildings without thermal insulation, the environmental effects of the type of fuel used to meet the heating load are as important as increasing the energy efficiency by reducing heat losses and thus reducing the need for heating. For this reason, the necessary analyses conducted by taking into account the emission values of the fuel types used for heating during the initial 14
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Fig. 20. The amount of CO2 equivalent of the building with different wall types, in which fuel oil is used for heating. a) Brick Wall b) Pumice Wall c) Aerated Concrete Wall d) Briquette Wall.
➢
➢
➢
➢
➢
material. In order to enable this calculation method to be applicable in a desired region, the equilibrium temperature for heating and cooling should be determined depending on the heat, humidity and solar radiation data of the respective region and the degree day values should be determined according to this equilibrium temperature. If these conditions are met, the analyses performed in this study will be applicable for the desired region.
design phase of the building will not only affect energy efficiency positively, but also the environment and human living standards, accordingly. As a result of the thermal insulation applied to the building, the heating requirement and the monthly fuel consumption and emissions decreased accordingly. In addition, the results to be obtained in this study will act as a guide for determining the saving values that can be obtained as a result of thermal insulation, and emission values according to the type of fuel used for heating need for a building that is already being used without thermal insulation. The calculations have revealed that the amount of payback period of the first investment required for the thermal insulation applied to the non-insulated wall models varies between 0.25 and 1.74 years after the insulation depending on the type of fuel and building material. The results also show that the payback period of the thermal insulation to be applied in the houses is low and that the gain obtained is positively reflected to the residents in the economic sense during the life of a building. With the improvements in buildings, a significant amount of energy will be saved not only in the heating period but also in the cooling period. Thereby, the thermal insulation to be made in houses will reduce the heating requirement of the building, directly reducing the fuel consumption on monthly and yearly basis. With the reduction of fuel consumption, the emission of pollutant gases released into the atmosphere during and after the combustion process will be reduced, and thus the greenhouse gas emissions that have a great impact on global warming will decline. The pollution caused by the combustion of fossil fuels used for heating the space in the winter when the heating demand is highest accounts for about 80% of the total pollution. Taking this into account, it is necessary to keep track of the air pollution caused by the housing heating and to determine the air quality standards according to the fuel used based on the data flow obtained from the follow-up. TS 825 is a comprehensive calculation method that includes factors such as the heating requirement of the building, the positioning of the building, the type of glass used in the building, the story height, the elements that will make shading around the building, the climatic conditions, the type of building material used, the internal energy gains, the type and thickness of the thermal insulation
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16
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Evaluation of a sample building with different type building elements in an energetic and environmental perspective
T
C. Ozalp∗, D.B. Saydam, K.N. Çerçi, E. Hürdoğan, H. Moran Department of Energy System Engineering, Faculty of Engineering, Osmaniye Korkut Ata University, Osmaniye, Turkey
ARTICLE INFO
ABSTRACT
Keywords: Energy efficiency Environment Numerical analyses Thermal insulation TS 825
The energy demand for heating in buildings in a residential area depends on the weather conditions of the area, the architectural characteristics and thermal-physical characteristics of the buildings, as well as the number of buildings in the settlement and the population of the settlement, accordingly. This study aimed to numerically determine the heat losses that may occur in case of different building materials (bricks, pumice, aerated concrete and briquettes) and insulation materials (XPS, EPS, rockwool and glass wool) used in the design of buildings, by applying the Finite Element Method (FEM) and considering the outdoor and indoor weather conditions proposed in Turkish Thermal Insulation Standard (TS 825). Then, the heating requirement according to the TS 825, the monthly fuel consumption, the payback period and the emission amounts in case of insulation were calculated for a model building with an external wall made of different building materials. In this study, the conditions of a model building located in Kahramanmaraş/Turkey were discussed separately in terms of being thermally insulated and non-insulated. As a result of the analyses obtained by using FEM, the effect of the wall building material on heat losses was found to be much higher than that of insulation material. Following the application of thermal insulation to the non-insulated building model, it was seen that the payback period of the first investment value required for the insulation application varied between 0.25 and 1.74 years depending on the type of fuel used for the heating energy requirement as well as on the type of building material. In the case of using briquette wall in the building, it seemed that the heating requirements, monthly fuel consumption and emission amounts were higher than those with other building materials. The briquette wall was followed by bricks, pumice and aerated concrete, respectively.
1. Introduction The industrial revolution has brought out urbanization and industrialization as a dominant outcome of economic and social modernization. Accordingly, the world's population growth and the energy demand that emerged with the impact of industrialization continues to increase with each passing day. The growing energy demand, in particular, has increased the use of fossil fuels (oil, natural gas, coal, fuel oil, etc.), which leads to increased CO2 and other greenhouse gas emissions [1]. As it is known that the world will run out of fossil fuels as an energy resource in the future, there have been efforts to make the efficient use of energy through legal regulations, both in Turkey and in the world. Particularly in buildings, certain levels of economic benefits can be achieved by energy efficiency measures and in like manner, harmful environmental factors can be reduced by diminishing the energy consumption [2]. With the purposes of reducing the energy consumption and
∗
preventing the use of conventional fuels causing greenhouse effect and further increase in CO2 emissions, extensive research on energy efficiency and energy conservation in buildings has been carried out in Turkey, where the significant amount of energy demand is imported [3] and fossil fuels are used in the power plants-especially in coal-fired power plants with low efficiency [4]. It is of great necessity to minimize the energy requirement for heating and cooling of buildings, to reduce the amount of energy consumed for illumination without compromising on comfort conditions, to minimize the amount of energy as much as possible and to take measures accordingly to provide energy conservation. One of the easy and efficient ways of preventing energy loss in buildings is the thermal insulation in buildings. The main purpose of placing the insulation material on the building envelope is to reduce the energy consumption for heating or cooling by increasing the thermal resistance of the building envelope [5]. One of the most important functions expected from the buildings is that they should provide suitable comfort conditions. Furthermore, one
Corresponding author. Tel.: +90 328 8271000x3502; Fax: +90 328 8250097. E-mail address: [email protected] (C. Ozalp).
https://doi.org/10.1016/j.rser.2019.109386 Received 19 March 2019; Received in revised form 5 August 2019; Accepted 8 September 2019 1364-0321/ © 2019 Elsevier Ltd. All rights reserved.
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of the most important parameters to be considered when examining the energy efficiency and energy inputs of a building is the thermal comfort of the residents. The comfort assessment of the residents is made using thermal comfort standards. These standards have a significant impact on evaluating the energy performance of buildings, and accordingly, on the energy consumption of buildings [6]. The standard for thermal insulation rules in buildings in Turkey are TS 825 (Turkish Thermal Insulation Standard) [7]. This standard aims to save energy by limiting energy consumption in the heating of buildings in Turkey, which forms an important part of the energy used. In the context of TS 825, Turkey is divided into four degree-day zones according to the climatic conditions of the cities from the hottest to the coldest. According to the calculation method of TS 825, the whole building is taken into consideration and the heat losses that may be caused by the floor, ceiling and exterior walls of the building are calculated. This standard aims to determine the annual heating energy requirement for buildings by taking into account the outdoor and indoor temperature values. In the method followed, heat loss and heat gain (solar energy, etc.) is calculated over monthly average meteorological values, and the annual heating energy requirement is specified by subtracting heat gains from heat losses. In the literature, it is possible to see many studies about thermal insulation applications in houses, determination of insulation thickness in thermal insulation, energy efficiency in buildings, energy and environmental problems originating from housing sector. In the literature, it is possible to see many studies about thermal insulation applications due to heat losses in houses, determination of insulation thickness in thermal insulation applications, energy efficiency in buildings, energy and environmental problems caused by housing sector [8–26]. Özkan and Onan [9], in their study, examined the effect of the windows and the wall area on the heating energy requirement of the building and the optimum insulation thickness by P1–P2 numerical calculation method. Moreover, they examined the changes in the variety of insulation materials, glass surfaces and fuel types as well as the optimum insulation thickness in four degree-day regions of Turkey in addition to the effect of the results on CO2 and SO2 emissions. As a result of the study, in the building which was constructed with extruded polystyrene foam (XPS) insulation material, in which natural gas and fuel oil was used as fuel and the ratio of the glass area to the external wall area was 0.2%, the energy savings were found as 13.996, 31.680, 46.613 and 63.071 $/m2, respectively and the payback period of the investment was 2.023, 1.836, 1.498 and 1.346 years in the four regions, respectively. In the event that XPS was used as the insulation material and natural gas as fuel, CO2 emissions were observed to decrease by 50.91%. In addition, CO2 and SO2 emissions decreased by 54.67% when XPS was used as insulation material and fuel oil as fuel. Romania et al. [26] conducted studies on buildings that account for the majority of energy consumption in Morocco. The authors studied the optimization of the building envelope to avoid high energy consumption of buildings and used the general regression approach for dynamic simulation. At the end of the study, the methodology revealed that the low energy buildings in Morocco could be successfully used for the optimization of the building envelope. Kazanasmaz et al. [27] aimed to determine the energy performance of the residences in İzmir, based on the relationship between energy performance and residential architecture. The authors focused on the energy consumption for heating purposes in the context of the Energy Efficiency Law [28], the Energy Performance Regulation in Buildings [29] and Standards Assessment Methods Related to Energy Quality of Housing (PEP-SDM), which are in force in Turkey. In the study, the energy performance evaluation method was conducted based on the Turkish standard TS 825 and the European standard EN ISO 13790. In the light of the regulations, the authors also determined that this study would help to estimate the energy performance of the buildings at the first design stage. In a study by Doymacı [30], the author identified all long-term daily temperatures taken from meteorological stations for all the provinces in Turkey and locations of heating degree days and cooling degree days of different provinces. In a
Fig. 1. Schematic view of the modelled wall; (1) internal plaster, (2) building material, (3) thermal insulation material, (4) external plaster.
study conducted by Dilmaç and Kesen [31], the writers compared TS 825, determined as the standards of thermal insulation in Turkey, with IS0 9164 and EN 832, as well as with the German standards. It was stated that each method had the same equations, the same constraints and the same flexibility. It was shown that the formulas used in the calculation of heating energy requirements were almost the same as those used in ISO 9164. However, in the German standard, the heating time in the whole country is accepted as a fixed value of 3500 K-days per year. In TS 825, it is known that there is a different heating day zone for each region. In addition, it is stated in ISO 9164 that it is impossible to perform calculations manually for Qmount, which refers to the outdoor temperature i.e. the daily average temperature and the monthly heating requirement. The study, however, showed that such calculations could be done manually for TS 825. On the other hand, EN 832 allows the calculation period to be selected as months or seasons, and the DD method to be uses. This shows that the procedures performed for all three methods are similar. Guattari et al. [32] used the FEM model to remanufacture a measuring device by using a 2D model measurement device instead of 1D in measuring the thermal resistance of the wall, and by including the internal heat sources into measurement. The main purpose of the study is to minimize the effect of internal heat sources to compare the thermal resistance of wall models with different heat resistance, and thus to obtain the best heat flow position. They compared this with a FEM model corresponding to the preliminary experimental results of the study. Bolattürk [33], calculated the optimum insulation thickness, energy savings and payback period by selecting cities from four different climatic regions of Turkey. The annual heating requirement of buildings in different climatic zones was determined by the degree-day method. The researchers first calculated the amount of heat loss through the exterior walls so as to calculate the optimum insulation thickness to be used on the exterior 2
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Fig. 2. Wall models and dimensions used in the calculations: (a) brick, (b) pumice, (c) aerated concrete. Table 1 Technical specifications of building materials [7]. Building Material
Thickness (m)
k (W/mK)
R (m2K/W)
Internal plastering External plastering Brick Pumice Aerated concrete Briquette
0.02 0.02 0.13 0.15 0.15 0.10
0.87 0.87 0.45 0.18 0.11 0.63
0.023 0.023 0.28 0.83 1.36 0.15
Table 2 Technical specifications of thermal insulation materials [40]. Thermal Insulation Material
k (W/mK)
Cost (TLa/m3)
Rockwool Glass wool EPS XPS
0.040 0.040 0.039 0.031
180 130 240 350
a
Exchange rate (selling): 1 Turkish Lira (TL) = 6.46 USD ($) announced at 3:30 p.m. on 7 September 2018 by the Central Bank of Turkey.
walls. In these calculations, the convection resistance of the internal and external environment and the transmission resistances of the wall and the insulating material were taken into consideration in order to determine the total heat transfer coefficient. Then, they determined the optimum insulation thickness for the exterior walls according to the life cycle cost analysis calculation method. In this study, five different types of fuel and a single insulation material were specified. It has been shown that the optimum insulation thickness varied between 2 and 17 cm, energy savings could be achieved between 22% and 79%, and the payback periods were between 1.3 and 4.5 years depending on the climate characteristics of the selected city and the type of fuel used. Ekici et al. [34], estimated the optimum insulation thickness, energy savings and payback periods by selecting four cities in different climate zones determined by Turkish Thermal Insulation Standard (TS 825). With the purpose of examining the heat losses, the researchers studied stone, brick and concrete building materials mostly used in practice for wall building in Turkey. They made calculations using four different
Fig. 3. Dimensions of the wall models used in the study.
thermal insulation materials and five types of fuel. During the calculations, first, the heat losses in the walls, which constitute a large part of the heat loss, were calculated by considering all the convection and transmission resistances between the internal and external environments surrounding the wall. Then, the writers determined the thermal insulation thickness for the walls according to the annual energy cost calculation method. As a result, the optimum insulation thickness ranged from 0.2 cm to 18.6 cm. Heat loss and optimum insulation thickness were observed when the concrete wall was used the most. It was also seen that energy savings ranged from $ 0.038/m2 to $ 250.415/m2, and payback times ranged from 0.714 to 9.104 years, depending on the city, the fuel and building materials used. Bellamy 2014 [35], in a study by Bellamy, the writer aimed to determine the effect of dynamic and equivalent U factors that can predict the relative energy performance of various wall designs in different climates. In this
Table 3 Properties of fuels chosen for using in estimations [29,41]. Fuel
Lower Heating Value (Hu)
Cost
CO2 Emission Conversion Factor FSEG (kg eq. CO2/kWh)
Combustion Efficiency η (%)
Natural Gas Coal (Imported) Fuel-Oil No:4
34.526 × 106 J/m3 29.295 × 106 J/kg 41.326 × 106 J/kg
1.119 TL/m3 1.190 TL/kg 3.100 TL/kg
0.234 0.433 0.330
90 66 80
3
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• Increase the amount of energy saving by considering the effect of •
building materials in houses and thus contribute to energy efficiency. Reduce the amount of fuel used for heating by diminishing the heat loss in the houses and reduce the carbon emissions of buildings.
In line with these objectives, it is aimed to present this study as a unique example of scientific research or engineering and architecture practices to be applied within the scope of energy efficiency in buildings. 2. Material and methods Thermal insulation is an effective element in reducing the heating and cooling loads to a minimum level by changing the thermo physical properties of the building envelope. Insulation is a practical and rational solution that plays an important role in energy saving [34]. It was stated that 25–40% of heat loss might occur through the walls of a building without thermal insulation, 23–27% through the roof, 9–10% through the windows, 13–15% from the ground, and 16–19% through infiltration (leakage) [36]. This study will examine the external walls of buildings with and without thermal insulation by considering the buildings constructed with different wall building materials widely used in Turkey in the past and those materials that have started to be used in recent years. Fig. 1 shows a schematic diagram of the wall model used in the calculations. In the study, four different building materials such as brick, pumice, aerated concrete and briquette were chosen for the external wall model on which thermal insulation would be applied. The choice of building materials and insulation materials was made by taking into account the thickness of the material, the average outside temperature of the region, thermal conductivity coefficient and price [37]. In recent years, there have been many improved insulation materials which have superior thermal insulation properties due to their low thermal conductivity [38]. Fig. 2 shows the schematic view of the wall models formed with different building materials and Table 1 gives the technical properties of the building materials which form the wall model. Table 2 shows the technical characteristics of the four different insulation materials discussed in the analysis [39]. Fuel costs and emissions for different fuels have also been evaluated in the study. Table 3 provides the technical specifications of the different fuels for which the evaluation is made. For numerical analysis using FEM, the governing equation involves heat transfer in solids [32]. It is given in Equation (1).
Fig. 4. The geometry of the wall models (a) and the structure of the mesh (b).
study, since these U factors are the parameters explaining the effects of heat mass, solar heat gain and insulation on the heat conduction through the building envelope, the importance of the effects of these parameters are emphasized. In this context, a simulation analysis was performed in eight cities to determine the energy performance of different wall designs and to determine the dynamic and equivalent Ufactors of these walls. The results show that there is a strong correlation between wall energy performance and the equivalent U factor, except for the coldest climatic zone. It is clear that this equivalent U factor can be considered as an indicator of wall energy performance for global housing. This study first analyzed numerically the heat losses which might occur when different insulation materials (XPS, EPS, rockwool and glass wool) were applied on various building materials (brick, pumice, aerated concrete and briquettes) used in a building model design by using Finite Elements Method (FEM). Then, the heating requirement, monthly fuel consumption, and payback period in case of insulation and the amount of emissions were examined for a sample building where external walls of different materials were used. This study has aimed to:
• Select the building and insulation materials well during the initial design stage of the houses and reduce the heat loss caused by building materials.
Fig. 5. Distribution of provinces according to the degree-day zones in TS 825 [7]. 4
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Fig. 6. Architectural drawings of the south facade (a), north facade (b), east/west facade (c), and the top view (d) of the building model used in the calculations.
cp
T + t
q= Q
the 2nd degree day zone in TS 825 were applied. According to this, indoor and outdoor temperatures were accepted as 19 °C and 13.6 °C respectively, and the heat transfer coefficient values of indoor and outdoor environment were taken as 7.7 W/m2K and 25 W/m2K respectively. Adiabatic boundary conditions (heat flux neglect at boundaries) were applied to the lower and upper boundaries of the wall. The thermal properties of the wall building materials were selected as indicated in Table 1 [7]. For numerical analysis using FEM, the dimensions of all walls were considered the same (Fig. 3). COMSOL Multiphysics Package Program was used for numerical analysis based on FEM method. Fig. 4 shows the geometry of the wall models and the mesh structure. The mesh structures of the wall models are triangular and consist of 892 elements. Turkey is divided into four main zones based on the number of degree-days (DG) according to TS 825 [7,38,42–44]. Fig. 5 shows the distribution of these zones on the map of Turkey. The calculations were carried out in the province of Kahramanmaras, which is within the 2nd
(1)
Here, ρ is the material density (kg//m3), cp is the specific heat capacity (J/kgK) at constant pressure, and Q is the heat source (J). Fourier law is used for the transmission of heat:
q=
k
(2)
T
Here, k is the thermal conductivity coefficient (W/mK), T is the temperature gradient (K), and q is the heat flux (W/m2). In order to perform heat transfer analyses at the boundaries of the structure, convection boundary conditions were applied to internal and external surfaces. Here, Newton's cooling law (equation (3)) was used.
q= h (Td s
(3)
T) 2
Here, h is the heat transfer coefficient (W/m K), Tout is the outdoor temperature (K), and T is the surface temperature (K). For the boundary conditions, the conditions specified according to 5
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Fig. 7. Temperature contour graphs in case of application of rockwool and glass wool as insulation materials in different types of wall models; (a) brick, (b) pumice, (c) aerated concrete, (d) briquette.
degree-day zone, located at latitude of 37.5° and a longitude of 36.9°, and at an altitude of 568 m. Fig. 6 shows the architectural drawings of the building model used in the calculations. The sample building had 250 m2 of floor space, 320 m2 of ceiling as well as 5 floors including the ground floor, with a 2.80 m of monolayer component between each floor. The annual heating energy requirement of the sample building was calculated according to whether the building was thermally insulated or non-insulated. In the calculations made for an insulated building, the external wall, floor and ceiling insulation thickness were taken as 4 cm, 5 cm and 5 cm respectively, taking into account the calculation method given in TS 825. Since all of the balcony doors were covered with glass at the time of the calculations, they were all included in the window area. The building chosen for this study has single-layer building materials. Additionally, it is assumed that the exterior surface of the building where the thermal insulation is applied is not connected to any building element since the building is detached. Building calculations were made
by ignoring a thermal bridge. The specific heat loss (H) of the building would have increased if the building had a thermal bridge. With the increase in the heat loss in the building, the annual heating requirement of the building would have increased in the same proportion. However, the thermal insulation thickness was determined within the scope of the conditions specified in TS-825 and it was assumed that insulation was applied to the outer shell of the whole building (including reinforced concrete elements that may form thermal bridges such as balconies, beams, columns and fasteners). In the light of these assumptions, it is expected that the effect of thermal bridge-induced heat loss will be very low. It is stated in the literature that thermal insulation applications will eliminate the formation of a thermal bridge [45–47], and in this study, it has been assumed that a good thermal insulation was applied to the whole outer shell of the building and thus, the formation of a thermal bridge was ignored. Also, it was assumed that there were no thermal bridges in the building. In addition, the soil contacting surface and the under-roof surface were adopted as standard for each zone. In 6
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Fig. 8. Temperature contour graphs in the case of applying EPS as insulation material in different types of wall models; (a) brick, (b) pumice, (c) aerated concrete, (d) briquette.
the study, only the heating load was calculated, but the calculation of condensation and cooling load were not included. Internal gains in the sample building were taken in accordance with TS 825. When calculating solar energy gains, the glasses were selected as standard double glazing. It was assumed that the building was under the influence of shadows like trees and within the building class of up to ten-storey buildings. In order to calculate the amount of energy consumed annually in the building model, it was necessary to determine the heat losses through the external walls of the building according to TS 825. Below are the equations used in the heat loss calculations.
Qy =
Qm
Qm = [H (
i
monthly average internal gains (W), s,m to monthly average external gains (W), t time (s). The specific heat loss in the building (H, W/K) is sum ofthe heat loss by means of conduction and convection (HT), and the heat loss through ventilation (Hv) [7]:
(4) e)
m ( i, m
+
s, m )].
t
H = HT + HV
(6)
HT =
AU + IUI
(7)
HV = . c. V I = 0,33. nh . Vh
(8)
An = 0,32. Vgross
(9)
U=
(5)
Here, Q y refers to the annual heating energy requirement (J), Q m to the monthly heating requirement (J), i monthly average internal temperature (°C), e monthly average outdoor temperature (°C), m to the monthly average use factor for gains (no units), i,m refers to the
R=
1 Ri + R + R e
(10)
d (11)
h 2
In the equations, A is the area of the building elements (m ) and U is the thermal conductivity coefficient of the building elements. It was 7
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Fig. 9. Temperature contour graphs in the case of applying XPS as insulating material in different types of wall models; (a) brick, (b) pumice, (c) aerated concrete, (d) briquette.
assumed that the building elements were designed in such a way that they would not condensate and no thermal bridges would form, and the inter-storey reinforced concrete was insulated in such a way that R resistance would be 0.8 as specified in TS 825. The “U” values of the building elements were determined using equation (10) according to the calculation method specified in the standard. Monthly internal gains in the building were calculated by using equation (12): s, m
=
ri, m xgi, m x Ii, m x Ai
m
GLRm = (
e(
(14)
1/ GLRm)
i,m
+
s,m)/H( i,m
e,m )
(15)
In the equations, Fw refers to the correction factor for the glasses (taken as 0.8 in calculations), g refers to the solar energy factor for the perpendicular surface (taken as 0.75 in calculations), and GLRm refers to the monthly average gain utilization factor. In the case that the GLRm value, which is a parameter of monthly heating requirement calculations, exceeds 2.5, it is accepted that there is no heat loss for that month. The months in which the GLRm is higher than 2.5 correspond to the summer months with hot climatic conditions where there is no need for heating. In the calculations, the heating requirement has a negative (−) value for the months in which the GLRm is higher than 2.5, and in the case that these values are included in the annual heating energy requirement, the results will be inaccurate. The TS 825 method carries out the process steps in order to avoid the miscalculation of the annual heating requirement, taking into account only the months when heating is required [7,31].
(12)
Here ri, m is the monthly average shading factor of transparent surfaces with the building storey height (m), and gi, m is the solar energy transmission factor. In calculations, ri, m was taken as 0.6 according to TS 825. The solar energy transmission factor was calculated by using equation (13) for the case where multi-layer glass was used, whereas the monthly average gain utilization factor was calculated with the following equation No.15.
gi, m = Fw . g
=1
(13) 8
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Fig. 10. The amount of heat transfer through the wall in the unit area per unit of time (heat flux) according to different wall and building materials.
Fig. 11. Variation of surface temperature of the inner wall according to different wall and building materials.
The feasibility of the thermal insulation was evaluated by considering the payback period (PP, year). The payback period is determined by the following equation.
C PP = ti NE
following equations according to the total energy consumption of the building and the type of fuel used [48].
SEGMy = By x Hu x FSEG
(16)
By =
In the equation, Cti, refers to the first investment cost required for thermal insulation (TL) and NE refers to the annual savings amount (TL/year) [41,49,50]. The amount of annual CO2 emissions was determined by using the
(17)
Q year Hu
k
(18)
Here, SEGMy refers to the annual amount of CO2 emission (kg equivalent CO2), Hu refers to lower heating value of the fuel (kJ/m3 or kJ/kg), By refers to the annual amount of fuel (m3 or kg), and FSEG 9
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Fig. 12. Distribution of temperature across the wall where different thermal insulation materials are applied to the same building materials; (a) brick, (b) pumice, (c) aerated concrete, (d) briquette.
refers to CO2 emission conversion coefficient according to the type of fuel (kg equivalent CO2/kWh) (Table 3), Hu indicates the lower heating value of the fuel, and the ηk indicates the combustion efficiency [29].
observed in the wall model where aerated concrete building material was used, while the highest heat loss was observed in the wall model where briquettes were used. The amounts of heat transfer (heat flux) values through the external wall in the unit area were calculated with the FEM method according to different wall and building materials per unit time (Fig. 10). As can be seen from Fig. 10, the least heat loss was in the wall model with aerated concrete building material (1.882 W//m2) and the most heat loss was in the wall model with briquette building material (3.714 W/m2). When the walls were compared with respect to the insulation materials, the least heat loss was seen when XPS insulation material was used and the most heat loss occurred in the cases where rockwool and glass wool insulation materials were used. Fig. 11 shows the change in surface temperatures of the inner wall, which was calculated numerically by FEM method according to different wall and building materials. The highest inner surface temperature values were achieved in the buildings with the aerated concrete, which causes the lowest heat loss. Likewise, the highest wall surface temperatures were obtained in the buildings where XPS insulation material was used, causing the least amount of heat loss. It was determined that the reason for this situation was due to the thermal properties of the wall building and insulation materials. While the wall temperature was higher in walls with building and insulation materials having a low heat conduction coefficient due to less amount of heat loss, the wall models with building and insulation materials having a high heat conduction coefficient had a lot of heat loss, as a result of which inner wall temperature can remain at lower values. Fig. 12 demonstrates the temperature distribution values obtained
3. Results and discussions In the study, firstly the heat losses that can occur in the application of different insulation materials (XPS, EPS, rockwool and glass wool) to building materials (brick, pumice, aerated concrete and briquettes) used in the design of the building model were calculated numerically using Finite Element Method and the results were evaluated. Fig. 7 shows the temperature contour distribution when rockwool and glass wool (the same thermal conductivity values, different places of use) were used as the insulation material for different wall building materials. When the temperature contour distributions are examined, it is observed that the most heat loss is in the wall model with briquette building material. It is also clear that the least heat loss is in the wall model with aerated concrete building material. Fig. 8 shows the distribution of the temperature in the contour plot in the case of the application of EPS material as insulation material to the different wall building materials. The contour graphs showed that the wall model with briquette building material had the most heat loss, whereas the least heat loss was in the wall model with aerated concrete building material. Fig. 9 shows the temperature distributions in the case of applying XPS material as insulation material to the different wall building materials in the contour plot. Similar results were obtained in this study as were found for the other insulation materials. The lowest heat loss was 10
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Fig. 13. Distribution of temperature values obtained across the wall when the same thermal insulation materials are applied to different building materials; (a) Rockwool, (b) Glass wool, (c) EPS, (d) XPS.
the briquette wall building materials were used. Furthermore, it is seen that the effect of wall building materials on heat loss was more than that of insulation materials. In the next section of the study, heating loads were calculated according to the external wall where four different building materials (brick, pumice, aerated concrete and briquette) were used for a sample building, based on which the amounts of monthly fuel consumption and emission were determined. The calculations were done separately according to whether or not the building was insulated, and the results were compared. The calculations made for the insulated building were carried out for a single insulation material by taking into account the FEM results. Considering the flammability class and heat conduction coefficient of the external wall structure of the building, rock wool was used and applied on different wall models. In addition, glass wool was used in the roof covering and XPS was used on the floor. Fig. 14 shows the graphs of comparing the monthly heating requirement of the building model with different building elements for thermally insulated or non-insulated cases. When the heating load of the building was examined, due to the high heat transfer coefficient of the wall structure formed from the briquette building material, the heat losses had the highest values among all the cases where other building materials were used. Following the briquette wall, the heating requirement are sorted from large to small as brick wall, pumice wall and aerated concrete wall, respectively. The graphs also demonstrate that there is a decrease in the heating requirement due to the application of thermal insulation. After determining the monthly heating requirements for the sample building, it was investigated at which costs these requirements could be met with different fuels. Figs. 15–17 demonstrate the costs incurring from meeting the heating requirements with natural gas, coal and fuel
Table 4 Payback period of the investment in the case of thermal insulation to thermally non-insulated wall models. Payback Period (year) Fuel Type
Brick Wall
Briquette Wall
Pumice Wall
Aerated Concrete Wall
Natural Gas Coal Fuel-oil
0.63 0.58 1.30
0.85 0.77 1.74
0.34 0.31 0.70
0.27 0.25 0.55
along the wall when different thermal insulation materials are applied to the same building materials. As can be seen from the figure, except for XPS, the temperature distributions of the other insulation materials are similar across the wall because their thermal conductivity coefficient values are close to each other. Fig. 13 and Table 4 demonstrates the distribution of temperature values obtained across the wall when the same thermal insulation materials were applied to different building materials. It is clear from the figure that the wall construction material is of great importance in insulation applications. The temperature difference between the inner surface and the external surface of the aerated concrete wall material, which had the lowest thermal conductivity, was highest. In this way, it was the wall building material that kept the interior environment at the highest value of the walls studied. Second was pumice concrete. However, it was found that the temperature difference between the inner surface and the external surface of the briquette wall was lower in the briquette wall building material than that of other wall building materials. This shows that the heat loss was mostly in the structures where 11
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Fig. 14. Comparison of the monthly heating requirement of the building model with different building elements for thermally insulated and non-insulated cases. a) Brick Wall b) Pumice Wall c) Aerated Concrete Wall d) Briquette Wall.
Fig. 15. Monthly fuel consumption of thermally insulated and non-insulated wall model consisting of different building elements when natural gas is used for heating. a) Briquette Wall b) Pumice Wall c) Aerated Concrete Wall d) Brick Wall.
oil, respectively in the case that different building materials were used, in relation to whether or not the building was insulated. As seen from the figures, the insulation of the building led to a significant decrease in the costs. In addition, the highest cost for all types of fuel appeared when the briquette material was used due to its heat transfer coefficient. The briquette wall was followed by brick, pumice and aerated concrete wall models. The payback period was taken into consideration in evaluating the insulation in terms of cost wise. Table 4 gives data for the payback periods (PP) estimated as a result of thermal insulation to the building when different building materials and different fuels were used. As seen from the table, PP values vary between 0.25 and 1.74 years depending
on the building material and fuel. In the sample building, the fuel consumption required to meet the monthly heating requirement was calculated and the CO2 (kg) equivalent of these fuel consumptions was determined. Figs. 18–20 demonstrate the CO2 (kg) equivalent values when the heating requirements were met with natural gas, coal and fuel oil, respectively in the case that different building materials were used, in relation to whether or not the building was insulated. As seen in Figs. 15–17, the insulation of the building reduced fuel consumption, thus resulting in a significant decrease in the amount of equivalent CO2. As a result of the combustion of the carbon molecules in the chemical structure of the coal, it releases many harmful wastes to the environment and the most 12
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Fig. 16. Monthly fuel consumption of thermally insulated and non-insulated wall model consisting of different building elements when coal is used for heating. a) Brick Wall b) Pumice Wall c) Aerated concrete Wall d) Briquette Wall.
Fig. 17. Monthly fuel consumption of thermally insulated and non-insulated wall model consisting of different building elements when fuel-oil is used for heating. a) Brick Wall b) Pumice Wall c) Aerated concrete Wall d) Briquette Wall.
important of these is CO2. As a result of calculations, it was found that coal had the highest emission value. Coal was followed by fuel oil and natural gas. Due to its chemical properties, natural gas does not contain much pollutant material compared to other fuels. The calculations revealed that natural gas had lower values than other fuels in terms of emissions. The figure also showed the maximum amount of CO2 equivalent for all fuel types emerging when the briquette material was used due to its heat conduction coefficient. The briquette wall was followed by brick, pumice and aerated concrete wall models.
sample building with different wall structures was calculated according to TS 825 during the heating season, in relation to whether or not the building was thermally insulated. The fuel consumption and the CO2 (kg) equivalent based emissions, which correspond to the heating requirements calculated according to the different building materials, were determined, and the sample building, energy cost and environmental aspects were examined. The results obtained from the study are given below: ➢ The heat loss calculations were performed numerically first by using Finite Elements Method and then the obtained results were compared by considering the different building and insulation materials. As a result of the numerical analysis, it was determined that the wall
4. Conclusions In this study, the heating energy requirement (heating load) for a 13
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Fig. 18. The amount of CO2 equivalent of the building with different wall types in which natural gas is used for heating. a) Brick Wall b) Pumice Wall c) Aerated Concrete Wall d) Briquette Wall.
Fig. 19. The amount of CO2 equivalent of the building with different wall types, in which coal is used for heating. a) Brick Wall b) Pumice Wall c) Aerated Concrete Wall d) Briquette Wall.
building material had a more effective role in reducing the heat losses than the insulation material. ➢ As a result of the calculations made for different wall building materials, the values in the building with the briquette wall model were higher than those of other building materials in terms of heating requirement and monthly fuel consumption. The building with a briquette wall was followed by the brick wall, pumice wall and the aerated concrete wall, respectively. It is necessary to analyse the building well at the initial design stage and select the building material accordingly in order to increase the amount of energy savings from the houses.
➢ In the scope of the study, the use of different building materials was also evaluated from an environmental point of view. Although the amount of emissions (kg equivalent CO2) varied according to the type of building material, the least amount was observed in natural gas compared to other fuels. Natural gas was followed by fuel oil and coal. For existing buildings without thermal insulation, the environmental effects of the type of fuel used to meet the heating load are as important as increasing the energy efficiency by reducing heat losses and thus reducing the need for heating. For this reason, the necessary analyses conducted by taking into account the emission values of the fuel types used for heating during the initial 14
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Fig. 20. The amount of CO2 equivalent of the building with different wall types, in which fuel oil is used for heating. a) Brick Wall b) Pumice Wall c) Aerated Concrete Wall d) Briquette Wall.
➢
➢
➢
➢
➢
material. In order to enable this calculation method to be applicable in a desired region, the equilibrium temperature for heating and cooling should be determined depending on the heat, humidity and solar radiation data of the respective region and the degree day values should be determined according to this equilibrium temperature. If these conditions are met, the analyses performed in this study will be applicable for the desired region.
design phase of the building will not only affect energy efficiency positively, but also the environment and human living standards, accordingly. As a result of the thermal insulation applied to the building, the heating requirement and the monthly fuel consumption and emissions decreased accordingly. In addition, the results to be obtained in this study will act as a guide for determining the saving values that can be obtained as a result of thermal insulation, and emission values according to the type of fuel used for heating need for a building that is already being used without thermal insulation. The calculations have revealed that the amount of payback period of the first investment required for the thermal insulation applied to the non-insulated wall models varies between 0.25 and 1.74 years after the insulation depending on the type of fuel and building material. The results also show that the payback period of the thermal insulation to be applied in the houses is low and that the gain obtained is positively reflected to the residents in the economic sense during the life of a building. With the improvements in buildings, a significant amount of energy will be saved not only in the heating period but also in the cooling period. Thereby, the thermal insulation to be made in houses will reduce the heating requirement of the building, directly reducing the fuel consumption on monthly and yearly basis. With the reduction of fuel consumption, the emission of pollutant gases released into the atmosphere during and after the combustion process will be reduced, and thus the greenhouse gas emissions that have a great impact on global warming will decline. The pollution caused by the combustion of fossil fuels used for heating the space in the winter when the heating demand is highest accounts for about 80% of the total pollution. Taking this into account, it is necessary to keep track of the air pollution caused by the housing heating and to determine the air quality standards according to the fuel used based on the data flow obtained from the follow-up. TS 825 is a comprehensive calculation method that includes factors such as the heating requirement of the building, the positioning of the building, the type of glass used in the building, the story height, the elements that will make shading around the building, the climatic conditions, the type of building material used, the internal energy gains, the type and thickness of the thermal insulation
Acknowledgements This study was supported by the Scientific Research Projects Unit of Osmaniye Korkut Ata University (OKÜBAP) within the scope of the project named as OKÜBAP-2018-PT3-010. Thanks to OKÜBAP for their support. References [1] Li K, Lin B. Impacts of urbanization and industrialization on energy consumption/ CO2 emissions: does the level of development matter? Renew Sustain Energy Rev 2015;52:1107–22https://doi.org/10.1016/j.rser.2015.07.185. [2] Dylewski R, Adamczyk J. Economic and environmental benefits of thermal insulation of building external walls. Build Environ 2011;46:2615–23https://doi.org/10. 1016/j.buildenv.2011.06.023. [3] Publications Office of the European Union. Energy transport and environment indicators the Luxembourg. https://ec.europa.eu/eurostat/documents/3217494/ 8435375/KS-DK-17-001-EN-N.pdf/18d1ecfd-acd8-4390-ade6-e1f858d746da; 2017, Accessed date: 5 December 2018. [4] Atilgan B, Azapagic A. Life cycle environmental impacts of electricity from fossil fuels in Turkey. J Clean Prod 2015;106:555–64https://doi.org/10.1016/j.jclepro. 2014.07.046. [5] Simona PL, Spiru P, Ion VI. Increasing the energy efficiency of buildings by thermal insulation. International scientific conference “environmental and climate technologies”, vol. 128. 2017. p. 393–9. Latvia: Energy Procedia https://doi.org/10. 1016/j.egypro.2017.09.044. [6] Serghidesa D, Dimitrioua S, Kyp I, Papanicolasa C. The adaptive comfort factor in evaluating the energy performance of office buildings in the mediterranean coastal cities. 9th international conference on sustainability in energy and buildings, vol. 134. Greece: Energy Procedia; 2017. p. 683–91https://doi.org/10.1016/j.egypro. 2017.09.588. [7] Turkish Standards Institute the TR. Turkish thermal insulation standard. www. resmigazete.gov.tr/eskiler/2008/08/20080826-7-1.doc; 2009, Accessed date: 3 July 2018. [8] Ubinasa ER, Rodrigueza S, Voss K, Todovic MS. Energy efficiency evaluation of zero energy houses. Energy Build 2014;83:23–35https://doi.org/10.1016/j.enbuild. 2014.06.019. [9] Özkan DB, Onan C. Optimization of insulation thickness for different glazing areas
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