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Study on ecological cost-effectiveness for the thermal insulation of building external vertical walls in Poland
Journal of Cleaner Production 133 (2016) 467e478
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Study on ecological cost-effectiveness for the thermal insulation of building external vertical walls in Poland Robert Dylewski a, *, Janusz Adamczyk b, 1 a b
ra, ul. Licealna 9, 65-417 Zielona Go ra, Poland Faculty of Mathematics, Computer Science and Econometrics, University of Zielona Go ra, ul. Licealna 9, 65-417 Zielona Go ra, Poland Faculty of Economics and Management, University of Zielona Go
a r t i c l e i n f o
a b s t r a c t
Article history: Received 2 January 2015 Received in revised form 24 April 2016 Accepted 24 May 2016 Available online 1 June 2016
Improving the energy efficiency of buildings is not a new issue. It is a challenge not only in Poland but also in many other European countries, which is proved by the actions and initiatives taken by the European Union. Due to the fact that Poland lies in a warm moderate temperate zone, with transition to the impact of marine and continental climate, the issue of thermal insulation of buildings is important in terms of economy and ecology. The paper proposes a method and an analysis of the ecological costeffectiveness for the investment involving the thermal insulation of external vertical walls for two different buildings in five climate zones located in Poland. The authors based their study on the life cycle assessment (LCA) technique. The analysis took into account different components, such as: heat sources, thermal insulation and construction materials, and usable areas of the analyzed buildings. Popular building materials on the Polish market, and more, were also included. The studies were performed on two single-family houses with a similar usable area, which are representative on the European market. The most favourable values of ecological cost-effectiveness were obtained among the examined options for most ecological thermal insulation material (eco-fibre), the type of heating with the highest environmental impact (electricity) and the most extreme (cold) climate occurring in Poland. The ecological payback period of thermal insulation investment for the studied variants were obtained in the range 0e6 years. The proposed method proved to be very helpful in assessing various options for thermal insulation investments. It can also be used in other places in the world. It allows to take into account both the environmental and economic aspects of the investment. This method could be useful for designers and energy/environmental auditors. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Cost-effectiveness Life cycle assessment Environmental benefits Thermal insulation Energy efficiency
1. Introduction Climate change is a global problem. It is believed that the effects of global warming will be, and often already are felt in all countries of the world. According to present knowledge, it is believed that human economic activity also contributes to the cause of these negative changes. Economic development leads to ever greater demand for energy, and the energy production usually uses nonrenewable natural resources. The European Union is facing unprecedented challenges resulting from the increasing dependence on energy imports and scarce energy resources and also the
* Corresponding author. Tel.: þ48 683282821; fax: þ48 683282801. E-mail addresses: [email protected] (R. Dylewski), J.Adamczyk@ wez.uz.zgora.pl (J. Adamczyk). 1 Tel.: þ48 683282237. http://dx.doi.org/10.1016/j.jclepro.2016.05.155 0959-6526/© 2016 Elsevier Ltd. All rights reserved.
necessity to reduce the previously mentioned climate changes (Katunsky et al., 2013; Roetzel and Tsangrassoulis, 2012). It is believed that improving energy efficiency is one of the best ways to tackle the challenges. It increases the level of security of EU energy supplies by reducing the primary energy consumption and the reduction of energy imports. It helps to reduce greenhouse gas emissions in a cost-effective way and thus helps the mitigation of climate change effects (Berger et al., 2014). One of the initiatives under the strategy “Europe 2020” is the flagship initiative entitled “Europe efficiently using resources” to help get economic growth independent from the resource use, the transition to a low carbon economy, greater use of renewable energy sources, modernize a transport sector and promote energy efficiency. It was accepted by the European Commission on 26 January 2011. According to its definition, energy efficiency is one of the most important elements for ensuring a sustainable use of energy resources (Communication, 2010). Polish economy, in spite
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of a real improvement in energy efficiency in recent years, is still characterized by excessive, more than twice higher than in other European Union countries, use of resources, materials and energy in the creation of gross national income. In the perspective of 2020 technical potential for energy efficiency is 50 percent, while economically justified even e 25 percent. The greatest potential for the energy efficiency improvement is attributed to construction sectors e residential and public buildings. In Poland, the thermal insulation of newly constructed residential buildings leads to a high demand for final energy of up to 120e150 kWh/m2 per year, while the values of this demand in so called old EU countries range between 40 and 90 kWh/m2 per year. A high demand for the final energy of residential buildings in Poland is a result of too liberal rules. At the current price level of energy and materials it is possible to build in a cost-effective way facilities with energy demand for heating at the level of 60e90 kWh/m2 per year. Taking into account technical capabilities, it is possible now to erect buildings in the standard of 15 kWh/m2 per year e this is the standard of a passive house (Arcipowska and Tomaszewska, 2012; Galvin, 2014). In order to improve the energy efficiency of buildings and reduce the load on the environment it is possible to increase the use of recycled building materials (Adamczyk and Dylewski, 2010). The aim of the article is to present the method of the ecological cost-effectiveness assessment for the investment involving thermal insulation of the building external vertical walls in the conditions of a moderate climate and to examine the effectiveness of the sample buildings depending on the condition of the building before thermal insulation, applied heat source and fuel and the type of thermal insulation material. 2. Characteristics of the analyzed residential buildings and their location The study examined two residential buildings with a standard usable area (meant as the area of single-family houses mostly built in Poland, approx. 150 m2). They were located on the territory with a moderate climate in Poland. The description of the analyzed buildings is presented in Appendix (Table A1). In both buildings external walls were erected in brick structure. It was considered that both buildings are new buildings. Depending on the type of a heat source, the following value of generation efficiency was adopted: coal boiler e 82%, condensing gas boiler e 94%, electricity boiler e 99%, heat pump e 350% (seasonal coefficient of pump performance SCOP ¼ 3.5). The construction of vertical walls in both buildings will be subjected to variation due to the material used to build this wall and the type and thickness of the thermal insulation material. To calculate the value of the heat demand a computer program CERTO v. 7.0.0.2 was used for performing the energy certification of singlefamily houses, apartment buildings, as well as buildings and objects of various service functions. It was developed by the Lower Silesian Agency for Energy and Environment (Certo, 2014). The article takes into account the variability of the location of buildings in different climatic zones in Poland. The entire Polish territory lies in the warm moderate zone, with the transition to the impact of marine and continental climate. Generally in northern and western parts of Poland moderate maritime climate prevails with mild, wet winters and cool summers with a lot of rainfall, while in the eastern part of the country there is a continental climate with harsh winters and hotter, and drier summers. The climate in Poland is significantly influenced by two main meteorological and non-meteorological factors. Meteorological _ factors are primarily the following ones (Kozuchowski, 2011): types of air masses in a particular area; distribution of fronts in different
seasons; the arrangement of main, low-pressure and high-pressure, atmospheric pressure centre. Non-meteorological factors include: latitude; distance from larger bodies of water; landform, altitude; the nature of the ground e surface active agent (type of vegetation: forests, meadows; water bodies: lakes, rivers; snow cover). In order to illustrate the difference in the demand for usable energy of the analyzed buildings, depending on the discussed climate zone, they will be located in each of the five areas highlighted in Poland. Poland was divided into five climate zones (see Fig. 1), marked by Roman numbers I, II, III, IV and V. Considering the locations of the discussed buildings in particular zones, due to the location of the weather stations, it was indicated: for zone I e the city of Szczecin; for zone II e the city of Zielona Gora (not marked on the map, it is in Lubuskie province, approx. 140 km south-west of Poznan); for zone III e the city of Kielce; for zone IV e Bialystok city and for zone V e the city of Suwalki (also not marked on the map, it is located in Podlasie province, away from Bialystok of approx. 120 km to the north). Table A2 (in Appendix) shows the coordinates of towns where the buildings are located. The average annual air temperature in Poland ranges between 6 and 8.5 C. The warmest regions are the Silesian Lowland (over 8.5 C) and the western part of the Sandomierz Basin (8 C). The lowest temperatures occur in the mountains, where there is their decrease with height (average 0.6 C at 100 m of elevation), which causes the occurrence of climatic superposition. In the south of Poland in the Tatra mountains on Kasprowy Mount the average annual air temperature is 0.8 C. Besides mountain areas, the coldest region of the country is Suwalki (about 6.5 C), hence one of the locations was provided there. Suwalki is often called the “Polish pole of cold”. The warmest month in Poland is July, while the coldest e January. Design outdoor temperature (see Table A2 in Appendix) according to EN 12831 (2006) corresponds to the computational air temperature outside the building. This table also shows the average annual outdoor temperature in each of the five climate zones in Poland. 3. Method of life cycle assessment The method of environmental life cycle assessment (LCA) was developed intensively in the last twenty years. In the literature it is possible to cite a lot of examples of its application in the issues related to energy or construction, among others, in Andersson et al. € fgren et al. (2011), Dzikuc (2013), (1998), Jeswani et al. (2010), Lo Lewandowska et al. (2013), Dylewski and Adamczyk (2014a, 2014b), and Hoxha et al. (2014). The method of environmental life cycle assessment is standardized on the basis of two standards ISO 14040 (ISO EN 14040, 2006) and ISO 14044 (ISO EN 14044, 2006). The LCA includes four basic steps described in the above standards:
Goal and Scope Definition; LCI e Life Cycle Inventory; LCIA e Life Cycle Impact Assessment; Interpretation.
The article defines the environmental impact of building thermal insulation materials used for the insulation of an external, vertical, opaque wall. The system of production covers the phase of production of thermal insulation materials with the phase of obtaining raw materials and energy for their production and use phase (so called energy phase) (Fig. 2). Energy phase is directly related to the thermal conductivity of particular materials, which in turn indirectly determines the building demand for thermal energy
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Fig. 1. The map of climate zones in Poland. Source: EN 12831 (2006).
Fig. 2. The production system and system boundaries for the life cycle of thermal insulation materials.
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Fig. 3. The production system and system boundaries for generating heat energy from different sources.
(Fig. 3). Besides the system, the recycling phase after the use for all materials was left, because Poland does not have the recycling system of thermal insulation and construction materials. Building waste is mostly used for curing the substrate. Also there is not a selective collection of construction waste. As a functional unit for thermal insulation materials, 1 m3 of material was adopted. However, for the building life cycle of the energy phase e the production of 1 kWh of thermal energy depending on the heat source used was taken as a functional unit. The essential elements required in the standards of ISO 14040 series conditioning to carry out effective and correct LCA analysis were articulated above. Using the LCA technique it is possible to make an assessment of an environmental impact of the following processes: raw material acquisition, production, distribution and disposal of the product. The realization of LCA analysis requires computer programs. The producers of this software include among others PE International GmbH e Gabi 4 program, ifu Hamburg GmbH e Umberto 5.0 pro Consultants e SimaPro 7.1 program and so on. These gram, PRe programs have been developed in European centres, and therefore they have databases relating to the average conditions in Europe, which is particularly important in terms of their use in Poland. In the article, the analysis used a computer program SimaPro 7.1 (SimaPro, 2009), which allows to use up to 21 procedures (methods) of assessment, out of which this paper uses a procedure Eco-indicator 99 (Adamczyk and Dzikuc, 2014; Pajchrowski et al., 2014). This procedure allows the unambiguous assignment of the eleven categories of impact to three categories of damage and thus allows to assess the impact on: human health, environmental quality and natural resource consumption. The above procedure also allows to make weighing and present the final result of LCA in eco-indicator point Pt. A value of 1 Pt represents 103 of annual
environmental load per capita in Europe. This value is calculated by dividing the entire burden on the environment in Europe by the number of inhabitants and multiplying by 1000 (scale factor).
4. Method of ecological cost-effectiveness assessment This section proposes a method for assessing the ecological costeffectiveness for the investment involving thermal insulation of the external vertical walls of the building. The thermal insulation of building walls has a significant impact on the reduction of thermal energy consumption in buildings in the use phase and, consequently, on the decrease of the load on the environment. The performance of the thermal insulation of the building external wall can be considered for environmental reasons as an investment, the aim of which is to reduce the burden on the environment. The costs of this investment are associated with the purchase, transport and performance of thermal insulation, while profits e with a reduction in demand for energy to heat the building. For the thermal insulation of the building external vertical walls, financial costs depend on the thickness of the thermal insulation layer, the cost of thermal insulation material used and the cost of the installation of thermal insulation. These costs per 1 m2 of the wall can be determined as follows:
Cf ¼ Km $d þ Kw where: 4.2 PLN z 1 V,
h
. i PLN m2 ;
(1)
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Km e cost of 1 m3 of thermal insulation material [PLN/m3], Kw e cost of thermal insulation installation for 1 m2 of the building wall [PLN/m2], d e thickness of a thermal insulation layer [m]. When examining the thermal insulation investment in ecological terms, “expenditures” are associated with an additional increase in the burden on the environment, and “income” with a reduced load on the environment as a result of realization of the investment. The ecological value of the investment VE, for 1 m2 of the wall surface, can be defined as follows:
VE ¼
n X
Ej
h . i Pt m2
(2)
Ej ¼ ðEUo EU Þ=p;
j ¼ 1; 2; …; n
471
h . i Pt m2 ;
(5)
where: EUo e LCA analysis result of one year of thermal phase of the building use, with the thermal transmittance Uo (for external building walls without thermal insulation) [Pt], EU e LCA analysis result of one year of thermal phase of the building use, with the thermal transmittance U (for external building walls with thermal insulation) [Pt], p e area of external vertical walls of the building [m2]. Value EU (similarly EUo) can be determined as follows:
j¼0
EU ¼ DU $pu $Ke
½Pt=y;
(6)
where: where: Ej < 0 e size of the increase of environmental load due to investment in a year (tj1, tj], Ej > 0 e size of the reduction of environmental load due to investment in a year (tj1, tj], n e number of years of thermal insulation use. The investment is considered to be ecologically profitable (it generates a reduction in environmental load) if the VE is nonnegative. Comparing several investments (by the indicator), this one with a greater value of VE is preferable. It is also possible to introduce the ecological indicator, expressed in units of time. As an ecological payback period, a shortest period [0, TE] was defined, for which the ecological value of all transfers Ej from this period is non-negative:
8 9 < = k X TE ¼ min tk : Ej 0 : ;
½y:
. VE
½PLN=Pt;
(7)
(3) where:
If VE < 0, the ecological payback period TE does not exist (the investment will increase the burden on the environment). Comparing several investments (due to the indicator), a better investment is considered the one, which has a smaller TE. For ecological reasons, expenditures (increasing load on the environment) are associated with the production of a thermal insulation material. They depend on the type of thermal insulation material and the thickness of a thermal insulation layer:
h . i Pt m2 ;
To compare different variants of thermal insulation it is also possible to apply a method of cost-effectiveness analysis (CEA). This method is used when measuring benefits takes place in units other than cash (e.g. when determining the environmental benefits e eco-points) (see MRR, 2007). For the investment involving the thermal insulation of building external walls, ecological costeffectiveness (indicator ECE) can be defined as the cost (in PLN) to reduce the environmental load of 1 Pt as a result of the investment:
ECE ¼ Cf
j¼0
E0 ¼ Kl $d
DU e annual heating energy demand for building per 1 m2 of usable area with a thermal transmittance U [kWh/m2 y], pu e usable area of the building [m2], Ke e LCA result of obtaining 1 kWh of thermal energy for a particular heat source [Pt/kWh].
(4)
Cf e financial costs of thermal insulation [PLN/m2], determined from formula (1); VE e value of the reduction of environmental load resulting from the installation of thermal insulation [Pt/m2], determined from formula (2). In Poland, the thickness of the thermal insulation layer should be selected in such a way as the thermally insulated external vertical walls have the thermal transmittance U 0.25 W/m2 K (in accordance with the relevant Regulation of the Minister of Infrastructure e RMT, 2013). In order to achieve the coefficient of UN ¼ 0.25 W/m2 K, the thickness dN of the thermal insulation should be (Laskowski, 2005):
where: Kl e LCA analysis result for 1 m3 of thermal insulation material [Pt/m3], d e as already defined in the paper. The income (reduction of the environmental load) occurs in the use phase of the building, because of the reduction in the energy consumption required to heat the building. The impact on ecological income is primarily related to: the heat source used and the properties of walls without and with thermal insulation:
dN ¼ l$ð1=UN 1=Uo Þ
½m;
(8)
where:
l e thermal conductivity of thermal insulation material [W/ m K], UN ¼ 0.25 [W/m2 K] e thermal transmittance of the wall with a thermal insulation layer, Uo e thermal transmittance of the wall without a thermal insulation layer [W/m2 K].
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It can also be specified for which value of the thermal transmittance of the wall with a layer of insulation Uopt net present value (NPV) of investment will be maximum and, consequently, at which thickness of the insulation dopt we obtain Uopt. It can be shown that due to U the function NPV (see Dylewski and Adamczyk, 2011)
NPV ¼ Cf þ Sn $Go $ðUo UÞ
h . i PLN m2
(9)
is concave and reaches a maximum value for
Uopt
sffiffiffiffiffiffiffiffiffiffiffi lKm ¼ Go Sn
h . i W m2 K :
(10)
The optimal thickness of thermal insulation corresponding to Uopt is then
dopt ¼ l$ 1 Uopt 1=Uo
½m;
(11)
where: P Sn ¼ nj¼1 ð1 þ sÞj =ð1 þ rÞj e cumulative discount factor, n e number of years of thermal insulation use, r e real annual interest rate, s e real annual growth (in percent) of the cost of heating, Go e annual cost of heating referred to 1 m2 of the surface of the analyzed external vertical wall [(PLN K)/(W y)], Cf, Uo, U, l, Km e as already defined in the paper. It is very important to estimate accurately the cost Go. It can be determined from the dependence:
Go $ðUo UN Þ ¼
pu ðDUo DUn Þ$ $Kc p
h
. i PLN m2 y :
(12)
Hence
Go ¼
DUo DUn pu $ $Kc Uo UN p
½ðPLN$KÞ=ðW$yÞ;
(13)
where: Kc e cost of generated heat for a particular heat source and fuel [PLN/kWh], other e as already defined in the paper. The proposed method of determining Go is much more accurate (error smaller than 1%) compared to the method based only on the degree-days (according to the examined variant the errors to 6% were obtained), which does not even take into account the proportion of usable space for the surface of the external vertical walls of the building pu/p. The demand for the heating energy of the building DUopt with the thermal transmittance Uopt (obtained from formula (10)) and the annual cost of heating Go (obtained from formula (13)) can be
then determined from the following formula:
p DUopt ¼ DUo Go $ Uo Uopt $ Pu
Kc
h
. i kWh m2 y :
(14)
5. Main results In this part there was determined ecological cost-effectiveness for the investment involving the thermal insulation of the building external vertical walls in accordance with the method set forth in Section 4. The effectiveness was examined for the buildings described in Section 2, depending on the condition of the building before thermal insulation, heat source and fuel used and type and thickness of the thermal insulation material. Finally, the climate zone in which the building is located was taken into consideration. Table 1 summarizes the most important data for the analyzed thermal insulation materials. The highest cost of purchase is for polyurethane, and the lowest for eco-fibre. However, thermal insulation properties for polyurethane are much better than ecofibre. The last row shows the results of the LCA analysis. The biggest environmental load is associated with the production of polyurethane, while for eco-fibre the environmental benefit was achieved (the material is made from recycled newspapers). Table 2 presents the parameters of the analyzed construction materials of the external wall. Three materials with different physical characteristics were proposed, which are popular among investors in Poland. The thermal transmittance Uo of the wall without a layer of thermal insulation was given in consideration of thermal resistance of plaster and the heat transfer resistance at the inner and outer surface with a horizontal direction of heat flow. The results of the analysis also depend substantially on a heat source used in the building. The key data for the selected types of heat sources are summarized in Table 3. The costs of generated heat Kc were determined taking into account the efficiency of generation and the cost of fuel or electricity. The last row shows the results of the LCA analysis of obtaining 1 kWh of thermal energy. By far the highest impact on the environment is attributed to an electricity boiler (S3) almost four times exceeding the value of the environmental impact of the natural gas boiler (S2), which has the lowest impact. Further calculations were made for residential buildings described in Section 2. The data on the usable areas (pu) and the area of external vertical walls (p) of the buildings is given from Appendix (Table A1). For further analysis the number of years of thermal insulation use n ¼ 25 years was adopted, and the values of interest rates r ¼ 5% and s ¼ 2%. As a result, the cumulative discount factor is Sn ¼ 17.5278. Table 4 shows the determined thicknesses of thermal insulation dN (see formula (8)) for norm thermal transmittance UN ¼ 0.25 W/ m2 K of the external vertical wall. On the basis of equation (13), for the designated by program CERTO demands for the building thermal energy DUo (with the
Table 1 Characteristics of thermal insulation materials. Thermal insulation material
EPS polystyrene (I1)
Mineral wool (I2)
Polyurethane foam PUR (I3)
Eco-fibre (I4)
Thermal conductivity l [W/m K] Cost of thermal insulat. material Km [PLN/m3] Cost of thermal insulat. installation Kw [PLN/m2] LCA result for thermal insul. mater. Kl [Pt/m3]
0.040 167.30 30.00 4.205
0.039 522.00 30.00 8.108
0.028 713.30 30.00 16.062
0.041 150.00 30.00 0.832
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Table 2 Characteristics of construction materials. Type of construction material
Cellular concrete blocks 500 (C1)
Ceramic hollow blocks MAX (C2)
Sand-lime blocs SILKA E (C3)
Thickness of the wall [m] Thermal resistance R [m2 K/W] Thermal transmittance of the wall without thermal insulation Uo [W/m2 K]
0.36 2.118 0.430
0.29 0.659 1.154
0.24 0.453 1.514
Table 3 Data on heat sources. Heat source
Hard coal boiler (S1)
Natural gas boiler (S2)
Electricity boiler (S3)
Heat pump (S4)
Cost of generated heat Kc [PLN/kWh] LCA result for thermal energy Ke [Pt/kWh]
0.116 0.0193
0.325 0.0123
0.586 0.0485
0.166 0.0137
Table 4 Thickness of thermal insulation dN [m] for norm thermal transmittance of the external vertical wall. Thermal insulation material
EPS polystyrene (I1)
Mineral wool (I2)
Polyurethane foam PUR (I3)
Eco-fibre (I4)
0.067 0.125 0.134
0.065 0.122 0.130
0.047 0.088 0.094
0.069 0.128 0.137
Type of construction material Cellular concrete blocks 500 (C1) Ceramic hollow blocks MAX (C2) Sand-lime blocs SILKA E (C3)
Table 5 Heating energy demand of the building B1 in [kWh/m2 y]. Climatic zone
DUo
DUn
Type of construction material
I II III IV V
C1
C2
C3
101.93 110.72 115.50 128.11 137.99
185.09 198.46 207.70 224.84 239.03
227.60 243.58 253.86 273.32 289.55
82.28 89.93 93.64 104.73 113.62
Table 6 Heating energy demand of the building B2 in [kWh/m2 y]. Climatic zone
DUn
DUo Type of construction material
I II III IV V
C1
C2
C3
122.63 132.27 139.37 151.84 162.42
202.07 216.68 226.32 243.37 257.74
241.35 258.35 269.72 288.91 305.23
103.17 111.79 117.46 129.22 138.75
thermal transmittance Uo) and DUn (with the thermal transmittance UN), annual heating costs Go were specified. The amounts of heating energy demand for the building B1 are given in Table 5. Table 6 summarizes the amounts of heat demand in the building B2. The demand is greater than in the building B1 respectively for the same variants (climate zone and type of the construction material). It should be noted how much the demand for heating energy depends on the type of construction material. For the analyzed variants, the demand with material C3 is about two times larger than with C1.
The smallest percentage difference in energy demand, between the extreme climate zones in Poland (I and V), is attributed to both buildings for the construction material of vertical wall C3 made of silicate. For this wall the demand for heat is 27.22% higher in zone V with respect to the zone I for the building B1. The same dependence for the building B2 is 26.47%. Obviously, the difference of the absolute values of the demand for vertical wall C3 is the highest among the considered cases. It can be noted that the more favourable thermal insulation properties of the construction material (lower values of coefficient U), the lower are the differences of absolute values in demand for thermal energy between the zones. Heating costs set for the building B1 are presented in Table 7. They depend mainly on the type of heat source used in the building and on the climate zone in which the building is situated. It should be noted that the building B2 obtained higher values of Go, among others, due to the higher value of pu/p. Further calculations were conducted for all variants. However, due to the large amount of data, in the following tables were given the results only for selected variants: building B1, construction materials C1 and C3, heat sources S1, S2 and S3, thermal insulation materials I1, I3 and I4, and climatic zones I, III and V. The optimal, for economic reasons, values of the thermal transmittance Uopt were determined (see formula (10)), which also depend significantly on the type of thermal insulation material. The results are summarized in Table 8. For most variants, Uopt was obtained lower than UN. For variant S1eI3, however, Uopt was obtained greater than UN, like there is a relation for S1eI2, S4eI2 and S4eI3. It can happen when there are relatively high costs of generating the heat (S1 and S4), and a relatively expensive thermal insulation material (I2 and I3). For a particular Uopt the heating energy demand DUopt can be determined (from formula (14)). As a result, the ecological value of the thermal insulation investment VE_opt can be determined (from formula (2)), with the thermal transmittance Uopt and the corresponding thermal insulation thickness dopt (see formula (11)). The results are given in Table 9. For all variants positive values were
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Table 7 Annual heating costs Go [(PLN$K)/(W$y)]. Type of construction material
Climatic zone
C1
Heat source
I II III IV V I II III IV V I II III IV V
C2
C3
S1
S2
S3
S4
8.593 9.092 9.559 10.224 10.657 8.952 9.450 9.932 10.458 10.920 9.050 9.568 9.978 10.499 10.956
24.075 25.472 26.783 28.645 29.858 25.081 26.477 27.826 29.302 30.595 25.355 26.808 27.954 29.415 30.695
43.409 45.928 48.292 51.650 53.837 45.223 47.739 50.172 52.833 55.164 45.716 48.337 50.404 53.037 55.346
12.297 13.010 13.680 14.631 15.251 12.811 13.523 14.212 14.966 15.627 12.950 13.693 14.278 15.024 15.678
Table 8 Optimal values of the thermal transmittance Uopt [W/m2 K]. Construction material
Climatic zone
C1
Heat source
I III V I III V
C3
S1
S2
S3
Thermal insulation material
Thermal insulation material
Thermal insulation material
I1
I3
I4
I1
I3
I4
I1
I3
I4
0.211 0.200 0.189 0.205 0.196 0.187
0.364 0.345 0.327 0.355 0.338 0.322
0.202 0.192 0.181 0.197 0.188 0.179
0.126 0.119 0.113 0.123 0.117 0.112
0.218 0.206 0.195 0.212 0.202 0.193
0.121 0.114 0.108 0.118 0.112 0.107
0.094 0.089 0.084 0.091 0.087 0.083
0.162 0.154 0.145 0.158 0.150 0.143
0.090 0.085 0.081 0.088 0.083 0.080
Table 9 The ecological value of thermal insulation investment VE_opt [Pt/m2]. Constr. material
Climatic zone
Heat source S2
S1 Thermal insulation material
C1
C3
I III V I III V
S3
Thermal insulation material
Thermal insulation material
I1
I3
I4
I1
I3
I4
I1
I3
I4
7.420 8.695 10.183 48.562 53.951 59.686
2.166 3.123 4.229 42.663 47.778 53.228
8.239 9.561 11.147 49.725 55.190 61.005
5.983 6.859 7.857 32.112 35.624 39.326
3.817 4.536 5.386 29.403 32.774 36.325
7.241 8.228 9.333 33.755 37.364 41.159
28.779 32.576 36.931 132.868 147.003 161.957
22.337 25.699 29.691 125.713 139.555 154.160
30.838 34.795 39.218 135.254 149.630 164.622
Table 10 The ecological value of thermal insulation investment VE_N [Pt/m2]. Constr. material
Climatic zone
Heat source S2
S1 Thermal insulation material
C1
C3
I III V I III V
S3
Thermal insulation material
Thermal insulation material
I1
I3
I4
I1
I3
I4
I1
I3
I4
6.152 6.875 7.697 47.016 51.895 57.039
5.679 6.402 7.224 46.069 50.948 56.092
6.491 7.214 8.036 47.693 52.572 57.716
3.818 4.279 4.803 29.760 32.869 36.147
3.345 3.806 4.330 28.813 31.922 35.200
4.157 4.618 5.142 30.437 33.546 36.824
15.885 17.704 19.769 119.002 131.261 144.187
15.412 17.231 19.296 118.055 130.314 143.240
16.224 18.043 20.108 119.679 131.938 144.864
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Table 11 Ecological cost-effectiveness ECEopt [PLN/Pt]. Constr. material
Climatic zone
Heat source S2
S1 Thermal insulation material
C1
C3
I III V I III V
S3
Thermal insulation material
Thermal insulation material
I1
I3
I4
I1
I3
I4
I1
I3
I4
6.23 5.51 4.90 1.20 1.11 1.03
17.80 13.26 10.64 1.71 1.58 1.47
5.61 4.99 4.45 1.15 1.06 0.99
11.28 10.30 9.38 2.49 2.32 2.17
19.63 17.78 15.90 3.79 3.53 3.32
9.18 8.46 7.78 2.31 2.16 2.03
2.98 2.75 2.55 0.75 0.70 0.66
4.79 4.41 4.09 1.14 1.07 1.01
2.72 2.53 2.34 0.71 0.67 0.62
The lowest (best) values in rows for the ecological cost-effectiveness.
Table 12 Ecological cost-effectiveness ECEN [PLN/Pt]. Constr. material
C1
C3
Climatic zone
I III V I III V
Heat source S1
S2
S3
Thermal insulation material
Thermal insulation material
Thermal insulation material
I1
I3
I4
I1
I3
I4
I1
I3
I4
6.70 5.99 5.35 1.11 1.01 0.92
11.19 9.92 8.79 2.11 1.90 1.73
6.22 5.59 5.02 1.06 0.96 0.88
10.79 9.63 8.58 1.76 1.59 1.45
18.99 16.69 14.67 3.37 3.04 2.76
9.71 8.74 7.85 1.66 1.51 1.37
2.59 2.33 2.08 0.44 0.40 0.36
4.12 3.69 3.29 0.82 0.74 0.68
2.49 2.24 2.01 0.42 0.38 0.35
The lowest (best) values in rows for the ecological cost-effectiveness.
Fig. 4. The ecological values of thermal insulation investment VE_N [Pt/m2] for selected variants, where. type of construction material: C1 e cellular concrete blocks, C3 e ceramic hollow blocks; heat source: S2 e natural gas boiler, S3 e electricity boiler; thermal insulation material: I3 e polyurethane foam, I4 e eco-fibre.
obtained, i.e. the reduction of environmental load due to the analyzed thermal insulation investment. However, the differences between variants are very large, the values depend significantly on all four factors taken into consideration: the climatic zone, the construction material of the wall, heat source used and thermal insulation material. The highest values VE_opt were obtained for the case of: construction material C3 (the smallest thermal resistance),
heat source S3 (the largest environmental load of producing 1 kWh of heat energy) and thermal insulation material I4 (the lowest value of the LCA result expressed in [Pt/m3]). Table 10 summarizes designated ecological values of the thermal insulation investment VE_N, with the thermal transmittance UN ¼ 0.25 W/m2 K and the thickness of thermal insulation dN. Comparing the results from Tables 9 and 10 it can be seen that
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Fig. 5. Ecological cost-effectiveness ECEN [PLN/Pt] for selected variants, where: type of construction material: C1 e cellular concrete blocks, C3 e ceramic hollow blocks; heat source: S2 e natural gas boiler, S3 e electricity boiler; thermal insulation material: I3 e polyurethane foam, I4 e eco-fibre.
wherever Uopt < UN we obtain VE_opt > VE_N. Due to the thermal insulation material the best results were obtained for eco-fibre (I4), as with the insulation thickness dopt. On the basis of ecological values of investment VE_opt and financial costs of thermal insulation Cf_opt, determined from formula (1) for dopt, the environmental cost-effectiveness ECEopt was calculated (see formula (7)). The results are shown in Table 11. Due to the type of thermal insulation material by far the smallest cost (in PLN) to reduce the environmental load by 1 Pt is obtained for eco-fibre (I4). Due to the type of the climatic zone the smallest cost of reducing the load on the environment is obtained in zone V, which is an area with the lowest average annual external and project temperatures. Similarly, the ecological cost-effectiveness ECEN was determined, with the thermal insulation thickness dN (see Table 12). Comparing ECEopt with ECEN for the same variants, sometimes the first value is greater and sometimes the other (yet the differences are not big) because the cost-effectiveness also depends significantly on the financial costs of thermal insulation. As it can be seen in Tables 11 and 12 that the differences in the ecological costeffectiveness between different variants are very large. This effectiveness depends significantly, like the ecological value of the investment, on the climate zone, construction material of the wall, heat source used and thermal insulation material. 6. Discussion It should be noted that the obtained results are to a large extent influenced by the condition of the building before thermal insulation. Both the ecological value of the investment VE and the ecological cost-effectiveness ECE were obtained by far the best when using silicate (C3) as a construction material. This material has definitely the worst thermal properties among the ones under consideration (see Table 2). A significant impact on the results is also exerted by the heating energy demand, which depends on the
climate zone. In zone V, this demand can be even more than 30% higher than in zone I. The best LCA result among the examined thermal insulation materials was obtained for eco-fibre (I4), which is also relatively inexpensive. Consequently, also VE and ECE were obtained the best for this insulation material. Using formula (3), the ecological payback period TE of the thermal insulation investment for all tested variants was also determined. The values in the range 0e6 years were obtained. This means that at the latest after 6 years the increase in the environment load as a result of thermal insulation performance will be eliminated by the reduction of environmental burden during the use phase of the building, due to the reduction in energy consumption to heat the building. For eco-fibre (I4) the payback period TE ¼ 0, because E0 is already positive (the production of eco-fibre reduces the burden on the environment). For other variants, the fastest payback takes place (after one or two years) when using heat source S1 or S3 and insulation material I1 or I2. The latest payback period was obtained for variant S2eI3, TE ¼ 5 with insulation thickness dN and TE ¼ 6 with insulation thickness dopt, both for building B1 and B2. It should be noted that for heat source S2 the best result of the LCA analysis was obtained (see Table 3), and for the insulation material I3 e the worst result of the LCA analysis (see Table 1). At the end, the graph (Fig. 4) summarizes the results for buildings B1 and B2 on the ecological value of thermal insulation investment VE_N (with the thermal transmittance UN ¼ 0.25 W/m2 K). There were selected variants, which obtained the smallest and largest values: (a) C1eS2eI3 in zone I, (b) C1eS3eI4 in zone V, (c) C3eS2eI3 in zone I and (d) C3eS3eI4 in zone V. Despite the large differences in the demand for heat between buildings B1 and B2 (see Tables 5 and 6), the differences in the obtained values VE_N are very small. The situation is similar in the case of VE_opt. As it was previously emphasized, the huge importance on ecological effects of the thermal insulation investment is given by: the condition of the building before thermal insulation, in particular construction material of the wall, heat source used and type of thermal insulation material.
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Fig. 5 summarizes the results for buildings B1 and B2 on the ecological cost-effectiveness of ECEN for the same variants as in Fig. 4. The differences between the buildings are very small. Just as for VE_N the values of this indicator depend primarily on the construction material of the wall, heat source used and type of thermal insulation material.
7. Conclusions The studies were carried out by locating the buildings in different zones in order to illustrate the variation of the size of the heat demand, and hence the impact on the environment. The demand for thermal energy for heating purposes in zone V was obtained by 38.1% higher than in zone I (for the building B1) and by 34.5% (for the building B2) for the variant, in which the external vertical walls were insulated in accordance with the applicable standards (UN ¼ 0.25 W/m2 K). Having the knowledge of the basic variables: location in the climatic zone, the type of heat source, the type of construction material of the wall and the type and thickness of thermal insulation, it is possible, using the method presented in the paper, to determine the ecological cost-effectiveness. It should be emphasized that all these factors have a strong influence on the results. The most favourable values of the ecological cost-effectiveness ECE expressed in [PLN/Pt], were obtained for the construction material of the wall with the worst thermal transmittance (silicate SILKA E), the most ecological thermal insulation material (eco-fibre), the type of heating with the worst result of the LCA analysis (electricity) and the most extreme (cold) climate occurring in Poland e
477
climatic zone V. On the other hand, the worst values ECE were obtained for the construction material of the wall with the best thermal transmittance (cellular concrete 500), the insulation material, which was the most expensive and had the worst LCA result (polyurethane PUR), the type of heating with the best result of the LCA analysis (natural gas) and climate zone I. It should also be noted that ecological payback period of thermal insulation investment for the studied variants was obtained in the range 0e6 years, which is at the latest after 6 years, the increase in the burden on the environment as a result of thermal insulation performance will be eliminated by the reduction of environmental load during the use phase of the building, due to the reduction in energy consumption to heat the building. The shortest payback periods were obtained for variants with thermal insulation made of eco-fibre (0 years), as already the production of eco-fibre reduces the burden on the environment. The latest payback periods were obtained for variants with a heat source e natural gas boiler and thermal insulation material e polyurethane PUR (5 or 6 years depending on the thickness of the insulation). The proposed method proved to be very helpful in assessing various options for thermal insulation investments. It can also be used in other places in the world. It allows to take into account both the environmental and economic aspects of the investment. This method could be useful for designers and energy/environmental auditors.
Appendix
Table A1 Description of the analyzed buildings.
2
Usable area pu [m ] Area of external vertical walls p [m2] Building volume [m3] Central heating systems
Ventilation system Heat accumulation efficiency Transport efficiency of the heating medium Efficiency regulation and utilization Computational averaged internal air temperature [ C] Heat gains [W/m2] Building structure
Window and door frames
House I (B1)
House II (B2)
140.20 206.61 376.14 Heating water pumps, thermally insulated pipes run in the wall furrows, in the floor and on the top of the walls; the living areas were designed with panel radiators and in the bathroom e towel rail radiators Natural/gravitational ventilation 97% 97%
144.70 200.26 383.48
98% 20 3.5 The design of a traditional brick, reinforced concrete floors, densely ribbed, wooden stairs, roof of a wooden structure, coverage of metal-tile roofing, mineral plaster provided on walls
The building construction is brick, ceilings e a “TERIVA” type, in the attic e a wooden roof, covering e tile or sheet metal, a roof pitch e 30 , mineral plaster
Window frames with diffusers, with thermal transmittance for the window frames U ¼ 1.3 W/m2 K, the outer door of the thermal transmittance U ¼ 1.8 W/m2 K
Table A2 Design outdoor temperature, average annual outdoor temperature and the coordinates of the cities. Climatic zone
Project outdoor temperature [ C]
Average annual outdoor temperature [ C]
City
Latitude
Longitude
I II III IV V
16 18 20 22 24
7.7 7.9 7.6 6.9 5.5
Szczecin ra Zielona Go Kielce Białystok Suwałki
53.430 N 51.940 N 50.889 N 53.139 N 54.109 N
14.529 E 15.489 E 20.649 E 23.159 E 22.940 E
Source: EN 12831 (2006).
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References Adamczyk, J., Dylewski, R., 2010. Recycling of construction waste in terms of sus w budowlanych w kontekscie budowtainable building (Recykling odpado wnowazonego). _ nictwa zro Probl. Ekorozw. Probl. Sustain. Dev. 5 (2), 125e131 (in Polish). Adamczyk, J., Dziku c, M., 2014. The analysis of suppositions included in the Polish energetic policy using the LCA technique e Poland case study. Renew. Sustain. Energy Rev. 39, 42e50. Andersson, K., Hùgaas, E.M., Lundqvist, U., Mattsson, B., 1998. The feasibility of including sustainability in LCA for product development. J. Clean. Prod. 6, 289e298. Arcipowska, A., Tomaszewska, A., 2012. The Efficiency of Energy Consumption e _ between Declarations, the Present State and the Future (Efektywnos c zuzycia energii e mie˛ dzy deklaracjami, stanem obecnym a przyszłoscia˛ ). Instytut na Rzecz Ekorozwoju, Warszawa, Poland. www.ine-isd.org.pl (20.06.20.) (in Polish). Berger, T., Amann, C., Formayer, H., Korjenic, A., Pospichal, B., Neururer, C., Smutny, R., 2014. Impacts of urban location and climate change upon energy demand of office buildings in Vienna, Austria. Build. Environ. 81, 258e269. Certo, 2014. http://cieplej.pl/index_daes.php5?dzial¼3&kat¼14 (06.06.14.). Communication, 2010. Communication from the Commission, Europe 2020. A Strategy for Smart, Sustainable and Inclusive Growth. European Commission, Brussels, 3.3.2010. Dylewski, R., Adamczyk, J., 2011. Economic and environmental benefits of thermal insulation of building external walls. Build. Environ. 46, 2615e2623. Dylewski, R., Adamczyk, J., 2014a. Life cycle assessment (LCA) of building thermal insulation materials. In: Pacheco-Torgal, F., Cabeza, L.F., Labrincha, J., de Magalhaes, A. (Eds.), Eco-Efficient Construction and Building Materials: LCA, Eco-Labelling and Case Studies. Woodhead Publishing Ltd., Cambridge, pp. 267e286. Dylewski, R., Adamczyk, J., 2014b. The comparison of thermal insulation types of plaster with cement plaster. J. Clean. Prod. 83, 256e262. Dziku c, M., 2013. Applying the life cycle assessment method to an analysis of the environmental impact of heat generation. Int. J. Appl. Mech. Eng. 18 (4), 1275e1281. EN 12831, 2006. EN 12831:2006P e Heating Systems in Buildings e Method for Calculation of the Design Heat Load. Galvin, R., 2014. Are passive houses economically viable? A reality-based, subjectivist approach to costebenefit analyses. Energy Build. 80, 149e157. Hoxha, E., Habert, G., Chevalier, J., Bazzana, M., Le Roy, R., 2014. Method to analyse
the contribution of material's sensitivity in building's environmental impact. J. Clean. Prod. 66, 54e64. ISO EN 14040, 2006. ISO EN 14040:2006 e Environmental Management e Life Cycle Assessment e Principles and Framework. ISO EN 14044, 2006. ISO EN 14044:2006 e Environmental Management e Life Cycle Assessment e Requirements and Guidelines. Jeswani, H.K., Azapagic, A., Schepelmann, P., Ritthoff, M., 2010. Options for broadening and deepening the LCA approaches. J. Clean. Prod. 18, 120e127. Katunsky, D., Korjenic, A., Katunska, J., Lopusniak, M., Korjenic, S., Doroudiani, S., 2013. Analysis of thermal energy demand and saving in industrial buildings: a case study in Slovakia. Build. Environ. 67, 138e146. _ Kozuchowski, K., 2011. Polish Climate (Klimat Polski). Wyd. PWN, Warszawa, Poland (in Polish). Laskowski, L., 2005. Thermal Protection and Energetic Performance of the Building (Ochrona cieplna i charakterystyka energetyczna budynku). Of. Wyd. Politechniki Warszawskiej, Warszawa, Poland (in Polish). Lewandowska, A., Noskowiak, A., Pajchrowski, G., 2013. Comparative life cycle assessment of passive and traditional residential buildings' use with a special focus on energy-related aspects. Energy Build. 67, 635e646. € fgren, B., Tillman, A.M., Rinde, B., 2011. Manufacturing actor's LCA. J. Clean. Prod. Lo 19, 2025e2033. MRR, 2007. Minister for Regional Development: National Strategic Reference Framework 2007e2013. The Guidance on the Selected Issues Related to the Preparation of Investment Projects, Including Revenue-Generating Projects (Minister Rozwoju Regionalnego: Narodowe Strategiczne Ramy Odniesienia zwia˛ zanych z przy2007e2013. Wytyczne w zakresie wybranych zagadnien w inwestycyjnych, w tym projekto w generuja˛ cych gotowaniem projekto d). Warszawa, Poland, 19.09.2007 (in Polish). docho Pajchrowski, G., Noskowiak, A., Lewandowska, A., Strykowski, W., 2014. Materials composition or energy characteristic e what is more important in environmental life cycle of buildings? Build. Environ. 72, 15e27. RMT, 2013. Regulation of the Minister of Transport, Construction and Maritime Economy on 5 July 2013 Amending the Regulation: on Technical Conditions to Be Met by Buildings and Their Location (Rozporza˛ dzenie Ministra Transportu, Budownictwa i Gospodarki Morskiej z dnia 5 lipca 2013 r. zmieniaja˛ ce rozw technicznych, jakim powinny odpowiada porza˛ dzenie w sprawie warunko c budynki i ich usytuowanie) (Dz.U. 2013 poz. 926) (in Polish). Roetzel, A., Tsangrassoulis, A., 2012. Impact of climate change on comfort and energy performance in offices. Build. Environ. 57, 349e361. Consultants, SimaPro LCA Software, Version 7.1. Product Ecology SimaPro, 2009. PRe Consultants, Netherlands. www.pre.nl/simapro (11.09.14.).
Contents lists available at ScienceDirect
Journal of Cleaner Production journal homepage: www.elsevier.com/locate/jclepro
Study on ecological cost-effectiveness for the thermal insulation of building external vertical walls in Poland Robert Dylewski a, *, Janusz Adamczyk b, 1 a b
ra, ul. Licealna 9, 65-417 Zielona Go ra, Poland Faculty of Mathematics, Computer Science and Econometrics, University of Zielona Go ra, ul. Licealna 9, 65-417 Zielona Go ra, Poland Faculty of Economics and Management, University of Zielona Go
a r t i c l e i n f o
a b s t r a c t
Article history: Received 2 January 2015 Received in revised form 24 April 2016 Accepted 24 May 2016 Available online 1 June 2016
Improving the energy efficiency of buildings is not a new issue. It is a challenge not only in Poland but also in many other European countries, which is proved by the actions and initiatives taken by the European Union. Due to the fact that Poland lies in a warm moderate temperate zone, with transition to the impact of marine and continental climate, the issue of thermal insulation of buildings is important in terms of economy and ecology. The paper proposes a method and an analysis of the ecological costeffectiveness for the investment involving the thermal insulation of external vertical walls for two different buildings in five climate zones located in Poland. The authors based their study on the life cycle assessment (LCA) technique. The analysis took into account different components, such as: heat sources, thermal insulation and construction materials, and usable areas of the analyzed buildings. Popular building materials on the Polish market, and more, were also included. The studies were performed on two single-family houses with a similar usable area, which are representative on the European market. The most favourable values of ecological cost-effectiveness were obtained among the examined options for most ecological thermal insulation material (eco-fibre), the type of heating with the highest environmental impact (electricity) and the most extreme (cold) climate occurring in Poland. The ecological payback period of thermal insulation investment for the studied variants were obtained in the range 0e6 years. The proposed method proved to be very helpful in assessing various options for thermal insulation investments. It can also be used in other places in the world. It allows to take into account both the environmental and economic aspects of the investment. This method could be useful for designers and energy/environmental auditors. © 2016 Elsevier Ltd. All rights reserved.
Keywords: Cost-effectiveness Life cycle assessment Environmental benefits Thermal insulation Energy efficiency
1. Introduction Climate change is a global problem. It is believed that the effects of global warming will be, and often already are felt in all countries of the world. According to present knowledge, it is believed that human economic activity also contributes to the cause of these negative changes. Economic development leads to ever greater demand for energy, and the energy production usually uses nonrenewable natural resources. The European Union is facing unprecedented challenges resulting from the increasing dependence on energy imports and scarce energy resources and also the
* Corresponding author. Tel.: þ48 683282821; fax: þ48 683282801. E-mail addresses: [email protected] (R. Dylewski), J.Adamczyk@ wez.uz.zgora.pl (J. Adamczyk). 1 Tel.: þ48 683282237. http://dx.doi.org/10.1016/j.jclepro.2016.05.155 0959-6526/© 2016 Elsevier Ltd. All rights reserved.
necessity to reduce the previously mentioned climate changes (Katunsky et al., 2013; Roetzel and Tsangrassoulis, 2012). It is believed that improving energy efficiency is one of the best ways to tackle the challenges. It increases the level of security of EU energy supplies by reducing the primary energy consumption and the reduction of energy imports. It helps to reduce greenhouse gas emissions in a cost-effective way and thus helps the mitigation of climate change effects (Berger et al., 2014). One of the initiatives under the strategy “Europe 2020” is the flagship initiative entitled “Europe efficiently using resources” to help get economic growth independent from the resource use, the transition to a low carbon economy, greater use of renewable energy sources, modernize a transport sector and promote energy efficiency. It was accepted by the European Commission on 26 January 2011. According to its definition, energy efficiency is one of the most important elements for ensuring a sustainable use of energy resources (Communication, 2010). Polish economy, in spite
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of a real improvement in energy efficiency in recent years, is still characterized by excessive, more than twice higher than in other European Union countries, use of resources, materials and energy in the creation of gross national income. In the perspective of 2020 technical potential for energy efficiency is 50 percent, while economically justified even e 25 percent. The greatest potential for the energy efficiency improvement is attributed to construction sectors e residential and public buildings. In Poland, the thermal insulation of newly constructed residential buildings leads to a high demand for final energy of up to 120e150 kWh/m2 per year, while the values of this demand in so called old EU countries range between 40 and 90 kWh/m2 per year. A high demand for the final energy of residential buildings in Poland is a result of too liberal rules. At the current price level of energy and materials it is possible to build in a cost-effective way facilities with energy demand for heating at the level of 60e90 kWh/m2 per year. Taking into account technical capabilities, it is possible now to erect buildings in the standard of 15 kWh/m2 per year e this is the standard of a passive house (Arcipowska and Tomaszewska, 2012; Galvin, 2014). In order to improve the energy efficiency of buildings and reduce the load on the environment it is possible to increase the use of recycled building materials (Adamczyk and Dylewski, 2010). The aim of the article is to present the method of the ecological cost-effectiveness assessment for the investment involving thermal insulation of the building external vertical walls in the conditions of a moderate climate and to examine the effectiveness of the sample buildings depending on the condition of the building before thermal insulation, applied heat source and fuel and the type of thermal insulation material. 2. Characteristics of the analyzed residential buildings and their location The study examined two residential buildings with a standard usable area (meant as the area of single-family houses mostly built in Poland, approx. 150 m2). They were located on the territory with a moderate climate in Poland. The description of the analyzed buildings is presented in Appendix (Table A1). In both buildings external walls were erected in brick structure. It was considered that both buildings are new buildings. Depending on the type of a heat source, the following value of generation efficiency was adopted: coal boiler e 82%, condensing gas boiler e 94%, electricity boiler e 99%, heat pump e 350% (seasonal coefficient of pump performance SCOP ¼ 3.5). The construction of vertical walls in both buildings will be subjected to variation due to the material used to build this wall and the type and thickness of the thermal insulation material. To calculate the value of the heat demand a computer program CERTO v. 7.0.0.2 was used for performing the energy certification of singlefamily houses, apartment buildings, as well as buildings and objects of various service functions. It was developed by the Lower Silesian Agency for Energy and Environment (Certo, 2014). The article takes into account the variability of the location of buildings in different climatic zones in Poland. The entire Polish territory lies in the warm moderate zone, with the transition to the impact of marine and continental climate. Generally in northern and western parts of Poland moderate maritime climate prevails with mild, wet winters and cool summers with a lot of rainfall, while in the eastern part of the country there is a continental climate with harsh winters and hotter, and drier summers. The climate in Poland is significantly influenced by two main meteorological and non-meteorological factors. Meteorological _ factors are primarily the following ones (Kozuchowski, 2011): types of air masses in a particular area; distribution of fronts in different
seasons; the arrangement of main, low-pressure and high-pressure, atmospheric pressure centre. Non-meteorological factors include: latitude; distance from larger bodies of water; landform, altitude; the nature of the ground e surface active agent (type of vegetation: forests, meadows; water bodies: lakes, rivers; snow cover). In order to illustrate the difference in the demand for usable energy of the analyzed buildings, depending on the discussed climate zone, they will be located in each of the five areas highlighted in Poland. Poland was divided into five climate zones (see Fig. 1), marked by Roman numbers I, II, III, IV and V. Considering the locations of the discussed buildings in particular zones, due to the location of the weather stations, it was indicated: for zone I e the city of Szczecin; for zone II e the city of Zielona Gora (not marked on the map, it is in Lubuskie province, approx. 140 km south-west of Poznan); for zone III e the city of Kielce; for zone IV e Bialystok city and for zone V e the city of Suwalki (also not marked on the map, it is located in Podlasie province, away from Bialystok of approx. 120 km to the north). Table A2 (in Appendix) shows the coordinates of towns where the buildings are located. The average annual air temperature in Poland ranges between 6 and 8.5 C. The warmest regions are the Silesian Lowland (over 8.5 C) and the western part of the Sandomierz Basin (8 C). The lowest temperatures occur in the mountains, where there is their decrease with height (average 0.6 C at 100 m of elevation), which causes the occurrence of climatic superposition. In the south of Poland in the Tatra mountains on Kasprowy Mount the average annual air temperature is 0.8 C. Besides mountain areas, the coldest region of the country is Suwalki (about 6.5 C), hence one of the locations was provided there. Suwalki is often called the “Polish pole of cold”. The warmest month in Poland is July, while the coldest e January. Design outdoor temperature (see Table A2 in Appendix) according to EN 12831 (2006) corresponds to the computational air temperature outside the building. This table also shows the average annual outdoor temperature in each of the five climate zones in Poland. 3. Method of life cycle assessment The method of environmental life cycle assessment (LCA) was developed intensively in the last twenty years. In the literature it is possible to cite a lot of examples of its application in the issues related to energy or construction, among others, in Andersson et al. € fgren et al. (2011), Dzikuc (2013), (1998), Jeswani et al. (2010), Lo Lewandowska et al. (2013), Dylewski and Adamczyk (2014a, 2014b), and Hoxha et al. (2014). The method of environmental life cycle assessment is standardized on the basis of two standards ISO 14040 (ISO EN 14040, 2006) and ISO 14044 (ISO EN 14044, 2006). The LCA includes four basic steps described in the above standards:
Goal and Scope Definition; LCI e Life Cycle Inventory; LCIA e Life Cycle Impact Assessment; Interpretation.
The article defines the environmental impact of building thermal insulation materials used for the insulation of an external, vertical, opaque wall. The system of production covers the phase of production of thermal insulation materials with the phase of obtaining raw materials and energy for their production and use phase (so called energy phase) (Fig. 2). Energy phase is directly related to the thermal conductivity of particular materials, which in turn indirectly determines the building demand for thermal energy
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Fig. 1. The map of climate zones in Poland. Source: EN 12831 (2006).
Fig. 2. The production system and system boundaries for the life cycle of thermal insulation materials.
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Fig. 3. The production system and system boundaries for generating heat energy from different sources.
(Fig. 3). Besides the system, the recycling phase after the use for all materials was left, because Poland does not have the recycling system of thermal insulation and construction materials. Building waste is mostly used for curing the substrate. Also there is not a selective collection of construction waste. As a functional unit for thermal insulation materials, 1 m3 of material was adopted. However, for the building life cycle of the energy phase e the production of 1 kWh of thermal energy depending on the heat source used was taken as a functional unit. The essential elements required in the standards of ISO 14040 series conditioning to carry out effective and correct LCA analysis were articulated above. Using the LCA technique it is possible to make an assessment of an environmental impact of the following processes: raw material acquisition, production, distribution and disposal of the product. The realization of LCA analysis requires computer programs. The producers of this software include among others PE International GmbH e Gabi 4 program, ifu Hamburg GmbH e Umberto 5.0 pro Consultants e SimaPro 7.1 program and so on. These gram, PRe programs have been developed in European centres, and therefore they have databases relating to the average conditions in Europe, which is particularly important in terms of their use in Poland. In the article, the analysis used a computer program SimaPro 7.1 (SimaPro, 2009), which allows to use up to 21 procedures (methods) of assessment, out of which this paper uses a procedure Eco-indicator 99 (Adamczyk and Dzikuc, 2014; Pajchrowski et al., 2014). This procedure allows the unambiguous assignment of the eleven categories of impact to three categories of damage and thus allows to assess the impact on: human health, environmental quality and natural resource consumption. The above procedure also allows to make weighing and present the final result of LCA in eco-indicator point Pt. A value of 1 Pt represents 103 of annual
environmental load per capita in Europe. This value is calculated by dividing the entire burden on the environment in Europe by the number of inhabitants and multiplying by 1000 (scale factor).
4. Method of ecological cost-effectiveness assessment This section proposes a method for assessing the ecological costeffectiveness for the investment involving thermal insulation of the external vertical walls of the building. The thermal insulation of building walls has a significant impact on the reduction of thermal energy consumption in buildings in the use phase and, consequently, on the decrease of the load on the environment. The performance of the thermal insulation of the building external wall can be considered for environmental reasons as an investment, the aim of which is to reduce the burden on the environment. The costs of this investment are associated with the purchase, transport and performance of thermal insulation, while profits e with a reduction in demand for energy to heat the building. For the thermal insulation of the building external vertical walls, financial costs depend on the thickness of the thermal insulation layer, the cost of thermal insulation material used and the cost of the installation of thermal insulation. These costs per 1 m2 of the wall can be determined as follows:
Cf ¼ Km $d þ Kw where: 4.2 PLN z 1 V,
h
. i PLN m2 ;
(1)
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Km e cost of 1 m3 of thermal insulation material [PLN/m3], Kw e cost of thermal insulation installation for 1 m2 of the building wall [PLN/m2], d e thickness of a thermal insulation layer [m]. When examining the thermal insulation investment in ecological terms, “expenditures” are associated with an additional increase in the burden on the environment, and “income” with a reduced load on the environment as a result of realization of the investment. The ecological value of the investment VE, for 1 m2 of the wall surface, can be defined as follows:
VE ¼
n X
Ej
h . i Pt m2
(2)
Ej ¼ ðEUo EU Þ=p;
j ¼ 1; 2; …; n
471
h . i Pt m2 ;
(5)
where: EUo e LCA analysis result of one year of thermal phase of the building use, with the thermal transmittance Uo (for external building walls without thermal insulation) [Pt], EU e LCA analysis result of one year of thermal phase of the building use, with the thermal transmittance U (for external building walls with thermal insulation) [Pt], p e area of external vertical walls of the building [m2]. Value EU (similarly EUo) can be determined as follows:
j¼0
EU ¼ DU $pu $Ke
½Pt=y;
(6)
where: where: Ej < 0 e size of the increase of environmental load due to investment in a year (tj1, tj], Ej > 0 e size of the reduction of environmental load due to investment in a year (tj1, tj], n e number of years of thermal insulation use. The investment is considered to be ecologically profitable (it generates a reduction in environmental load) if the VE is nonnegative. Comparing several investments (by the indicator), this one with a greater value of VE is preferable. It is also possible to introduce the ecological indicator, expressed in units of time. As an ecological payback period, a shortest period [0, TE] was defined, for which the ecological value of all transfers Ej from this period is non-negative:
8 9 < = k X TE ¼ min tk : Ej 0 : ;
½y:
. VE
½PLN=Pt;
(7)
(3) where:
If VE < 0, the ecological payback period TE does not exist (the investment will increase the burden on the environment). Comparing several investments (due to the indicator), a better investment is considered the one, which has a smaller TE. For ecological reasons, expenditures (increasing load on the environment) are associated with the production of a thermal insulation material. They depend on the type of thermal insulation material and the thickness of a thermal insulation layer:
h . i Pt m2 ;
To compare different variants of thermal insulation it is also possible to apply a method of cost-effectiveness analysis (CEA). This method is used when measuring benefits takes place in units other than cash (e.g. when determining the environmental benefits e eco-points) (see MRR, 2007). For the investment involving the thermal insulation of building external walls, ecological costeffectiveness (indicator ECE) can be defined as the cost (in PLN) to reduce the environmental load of 1 Pt as a result of the investment:
ECE ¼ Cf
j¼0
E0 ¼ Kl $d
DU e annual heating energy demand for building per 1 m2 of usable area with a thermal transmittance U [kWh/m2 y], pu e usable area of the building [m2], Ke e LCA result of obtaining 1 kWh of thermal energy for a particular heat source [Pt/kWh].
(4)
Cf e financial costs of thermal insulation [PLN/m2], determined from formula (1); VE e value of the reduction of environmental load resulting from the installation of thermal insulation [Pt/m2], determined from formula (2). In Poland, the thickness of the thermal insulation layer should be selected in such a way as the thermally insulated external vertical walls have the thermal transmittance U 0.25 W/m2 K (in accordance with the relevant Regulation of the Minister of Infrastructure e RMT, 2013). In order to achieve the coefficient of UN ¼ 0.25 W/m2 K, the thickness dN of the thermal insulation should be (Laskowski, 2005):
where: Kl e LCA analysis result for 1 m3 of thermal insulation material [Pt/m3], d e as already defined in the paper. The income (reduction of the environmental load) occurs in the use phase of the building, because of the reduction in the energy consumption required to heat the building. The impact on ecological income is primarily related to: the heat source used and the properties of walls without and with thermal insulation:
dN ¼ l$ð1=UN 1=Uo Þ
½m;
(8)
where:
l e thermal conductivity of thermal insulation material [W/ m K], UN ¼ 0.25 [W/m2 K] e thermal transmittance of the wall with a thermal insulation layer, Uo e thermal transmittance of the wall without a thermal insulation layer [W/m2 K].
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It can also be specified for which value of the thermal transmittance of the wall with a layer of insulation Uopt net present value (NPV) of investment will be maximum and, consequently, at which thickness of the insulation dopt we obtain Uopt. It can be shown that due to U the function NPV (see Dylewski and Adamczyk, 2011)
NPV ¼ Cf þ Sn $Go $ðUo UÞ
h . i PLN m2
(9)
is concave and reaches a maximum value for
Uopt
sffiffiffiffiffiffiffiffiffiffiffi lKm ¼ Go Sn
h . i W m2 K :
(10)
The optimal thickness of thermal insulation corresponding to Uopt is then
dopt ¼ l$ 1 Uopt 1=Uo
½m;
(11)
where: P Sn ¼ nj¼1 ð1 þ sÞj =ð1 þ rÞj e cumulative discount factor, n e number of years of thermal insulation use, r e real annual interest rate, s e real annual growth (in percent) of the cost of heating, Go e annual cost of heating referred to 1 m2 of the surface of the analyzed external vertical wall [(PLN K)/(W y)], Cf, Uo, U, l, Km e as already defined in the paper. It is very important to estimate accurately the cost Go. It can be determined from the dependence:
Go $ðUo UN Þ ¼
pu ðDUo DUn Þ$ $Kc p
h
. i PLN m2 y :
(12)
Hence
Go ¼
DUo DUn pu $ $Kc Uo UN p
½ðPLN$KÞ=ðW$yÞ;
(13)
where: Kc e cost of generated heat for a particular heat source and fuel [PLN/kWh], other e as already defined in the paper. The proposed method of determining Go is much more accurate (error smaller than 1%) compared to the method based only on the degree-days (according to the examined variant the errors to 6% were obtained), which does not even take into account the proportion of usable space for the surface of the external vertical walls of the building pu/p. The demand for the heating energy of the building DUopt with the thermal transmittance Uopt (obtained from formula (10)) and the annual cost of heating Go (obtained from formula (13)) can be
then determined from the following formula:
p DUopt ¼ DUo Go $ Uo Uopt $ Pu
Kc
h
. i kWh m2 y :
(14)
5. Main results In this part there was determined ecological cost-effectiveness for the investment involving the thermal insulation of the building external vertical walls in accordance with the method set forth in Section 4. The effectiveness was examined for the buildings described in Section 2, depending on the condition of the building before thermal insulation, heat source and fuel used and type and thickness of the thermal insulation material. Finally, the climate zone in which the building is located was taken into consideration. Table 1 summarizes the most important data for the analyzed thermal insulation materials. The highest cost of purchase is for polyurethane, and the lowest for eco-fibre. However, thermal insulation properties for polyurethane are much better than ecofibre. The last row shows the results of the LCA analysis. The biggest environmental load is associated with the production of polyurethane, while for eco-fibre the environmental benefit was achieved (the material is made from recycled newspapers). Table 2 presents the parameters of the analyzed construction materials of the external wall. Three materials with different physical characteristics were proposed, which are popular among investors in Poland. The thermal transmittance Uo of the wall without a layer of thermal insulation was given in consideration of thermal resistance of plaster and the heat transfer resistance at the inner and outer surface with a horizontal direction of heat flow. The results of the analysis also depend substantially on a heat source used in the building. The key data for the selected types of heat sources are summarized in Table 3. The costs of generated heat Kc were determined taking into account the efficiency of generation and the cost of fuel or electricity. The last row shows the results of the LCA analysis of obtaining 1 kWh of thermal energy. By far the highest impact on the environment is attributed to an electricity boiler (S3) almost four times exceeding the value of the environmental impact of the natural gas boiler (S2), which has the lowest impact. Further calculations were made for residential buildings described in Section 2. The data on the usable areas (pu) and the area of external vertical walls (p) of the buildings is given from Appendix (Table A1). For further analysis the number of years of thermal insulation use n ¼ 25 years was adopted, and the values of interest rates r ¼ 5% and s ¼ 2%. As a result, the cumulative discount factor is Sn ¼ 17.5278. Table 4 shows the determined thicknesses of thermal insulation dN (see formula (8)) for norm thermal transmittance UN ¼ 0.25 W/ m2 K of the external vertical wall. On the basis of equation (13), for the designated by program CERTO demands for the building thermal energy DUo (with the
Table 1 Characteristics of thermal insulation materials. Thermal insulation material
EPS polystyrene (I1)
Mineral wool (I2)
Polyurethane foam PUR (I3)
Eco-fibre (I4)
Thermal conductivity l [W/m K] Cost of thermal insulat. material Km [PLN/m3] Cost of thermal insulat. installation Kw [PLN/m2] LCA result for thermal insul. mater. Kl [Pt/m3]
0.040 167.30 30.00 4.205
0.039 522.00 30.00 8.108
0.028 713.30 30.00 16.062
0.041 150.00 30.00 0.832
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Table 2 Characteristics of construction materials. Type of construction material
Cellular concrete blocks 500 (C1)
Ceramic hollow blocks MAX (C2)
Sand-lime blocs SILKA E (C3)
Thickness of the wall [m] Thermal resistance R [m2 K/W] Thermal transmittance of the wall without thermal insulation Uo [W/m2 K]
0.36 2.118 0.430
0.29 0.659 1.154
0.24 0.453 1.514
Table 3 Data on heat sources. Heat source
Hard coal boiler (S1)
Natural gas boiler (S2)
Electricity boiler (S3)
Heat pump (S4)
Cost of generated heat Kc [PLN/kWh] LCA result for thermal energy Ke [Pt/kWh]
0.116 0.0193
0.325 0.0123
0.586 0.0485
0.166 0.0137
Table 4 Thickness of thermal insulation dN [m] for norm thermal transmittance of the external vertical wall. Thermal insulation material
EPS polystyrene (I1)
Mineral wool (I2)
Polyurethane foam PUR (I3)
Eco-fibre (I4)
0.067 0.125 0.134
0.065 0.122 0.130
0.047 0.088 0.094
0.069 0.128 0.137
Type of construction material Cellular concrete blocks 500 (C1) Ceramic hollow blocks MAX (C2) Sand-lime blocs SILKA E (C3)
Table 5 Heating energy demand of the building B1 in [kWh/m2 y]. Climatic zone
DUo
DUn
Type of construction material
I II III IV V
C1
C2
C3
101.93 110.72 115.50 128.11 137.99
185.09 198.46 207.70 224.84 239.03
227.60 243.58 253.86 273.32 289.55
82.28 89.93 93.64 104.73 113.62
Table 6 Heating energy demand of the building B2 in [kWh/m2 y]. Climatic zone
DUn
DUo Type of construction material
I II III IV V
C1
C2
C3
122.63 132.27 139.37 151.84 162.42
202.07 216.68 226.32 243.37 257.74
241.35 258.35 269.72 288.91 305.23
103.17 111.79 117.46 129.22 138.75
thermal transmittance Uo) and DUn (with the thermal transmittance UN), annual heating costs Go were specified. The amounts of heating energy demand for the building B1 are given in Table 5. Table 6 summarizes the amounts of heat demand in the building B2. The demand is greater than in the building B1 respectively for the same variants (climate zone and type of the construction material). It should be noted how much the demand for heating energy depends on the type of construction material. For the analyzed variants, the demand with material C3 is about two times larger than with C1.
The smallest percentage difference in energy demand, between the extreme climate zones in Poland (I and V), is attributed to both buildings for the construction material of vertical wall C3 made of silicate. For this wall the demand for heat is 27.22% higher in zone V with respect to the zone I for the building B1. The same dependence for the building B2 is 26.47%. Obviously, the difference of the absolute values of the demand for vertical wall C3 is the highest among the considered cases. It can be noted that the more favourable thermal insulation properties of the construction material (lower values of coefficient U), the lower are the differences of absolute values in demand for thermal energy between the zones. Heating costs set for the building B1 are presented in Table 7. They depend mainly on the type of heat source used in the building and on the climate zone in which the building is situated. It should be noted that the building B2 obtained higher values of Go, among others, due to the higher value of pu/p. Further calculations were conducted for all variants. However, due to the large amount of data, in the following tables were given the results only for selected variants: building B1, construction materials C1 and C3, heat sources S1, S2 and S3, thermal insulation materials I1, I3 and I4, and climatic zones I, III and V. The optimal, for economic reasons, values of the thermal transmittance Uopt were determined (see formula (10)), which also depend significantly on the type of thermal insulation material. The results are summarized in Table 8. For most variants, Uopt was obtained lower than UN. For variant S1eI3, however, Uopt was obtained greater than UN, like there is a relation for S1eI2, S4eI2 and S4eI3. It can happen when there are relatively high costs of generating the heat (S1 and S4), and a relatively expensive thermal insulation material (I2 and I3). For a particular Uopt the heating energy demand DUopt can be determined (from formula (14)). As a result, the ecological value of the thermal insulation investment VE_opt can be determined (from formula (2)), with the thermal transmittance Uopt and the corresponding thermal insulation thickness dopt (see formula (11)). The results are given in Table 9. For all variants positive values were
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Table 7 Annual heating costs Go [(PLN$K)/(W$y)]. Type of construction material
Climatic zone
C1
Heat source
I II III IV V I II III IV V I II III IV V
C2
C3
S1
S2
S3
S4
8.593 9.092 9.559 10.224 10.657 8.952 9.450 9.932 10.458 10.920 9.050 9.568 9.978 10.499 10.956
24.075 25.472 26.783 28.645 29.858 25.081 26.477 27.826 29.302 30.595 25.355 26.808 27.954 29.415 30.695
43.409 45.928 48.292 51.650 53.837 45.223 47.739 50.172 52.833 55.164 45.716 48.337 50.404 53.037 55.346
12.297 13.010 13.680 14.631 15.251 12.811 13.523 14.212 14.966 15.627 12.950 13.693 14.278 15.024 15.678
Table 8 Optimal values of the thermal transmittance Uopt [W/m2 K]. Construction material
Climatic zone
C1
Heat source
I III V I III V
C3
S1
S2
S3
Thermal insulation material
Thermal insulation material
Thermal insulation material
I1
I3
I4
I1
I3
I4
I1
I3
I4
0.211 0.200 0.189 0.205 0.196 0.187
0.364 0.345 0.327 0.355 0.338 0.322
0.202 0.192 0.181 0.197 0.188 0.179
0.126 0.119 0.113 0.123 0.117 0.112
0.218 0.206 0.195 0.212 0.202 0.193
0.121 0.114 0.108 0.118 0.112 0.107
0.094 0.089 0.084 0.091 0.087 0.083
0.162 0.154 0.145 0.158 0.150 0.143
0.090 0.085 0.081 0.088 0.083 0.080
Table 9 The ecological value of thermal insulation investment VE_opt [Pt/m2]. Constr. material
Climatic zone
Heat source S2
S1 Thermal insulation material
C1
C3
I III V I III V
S3
Thermal insulation material
Thermal insulation material
I1
I3
I4
I1
I3
I4
I1
I3
I4
7.420 8.695 10.183 48.562 53.951 59.686
2.166 3.123 4.229 42.663 47.778 53.228
8.239 9.561 11.147 49.725 55.190 61.005
5.983 6.859 7.857 32.112 35.624 39.326
3.817 4.536 5.386 29.403 32.774 36.325
7.241 8.228 9.333 33.755 37.364 41.159
28.779 32.576 36.931 132.868 147.003 161.957
22.337 25.699 29.691 125.713 139.555 154.160
30.838 34.795 39.218 135.254 149.630 164.622
Table 10 The ecological value of thermal insulation investment VE_N [Pt/m2]. Constr. material
Climatic zone
Heat source S2
S1 Thermal insulation material
C1
C3
I III V I III V
S3
Thermal insulation material
Thermal insulation material
I1
I3
I4
I1
I3
I4
I1
I3
I4
6.152 6.875 7.697 47.016 51.895 57.039
5.679 6.402 7.224 46.069 50.948 56.092
6.491 7.214 8.036 47.693 52.572 57.716
3.818 4.279 4.803 29.760 32.869 36.147
3.345 3.806 4.330 28.813 31.922 35.200
4.157 4.618 5.142 30.437 33.546 36.824
15.885 17.704 19.769 119.002 131.261 144.187
15.412 17.231 19.296 118.055 130.314 143.240
16.224 18.043 20.108 119.679 131.938 144.864
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475
Table 11 Ecological cost-effectiveness ECEopt [PLN/Pt]. Constr. material
Climatic zone
Heat source S2
S1 Thermal insulation material
C1
C3
I III V I III V
S3
Thermal insulation material
Thermal insulation material
I1
I3
I4
I1
I3
I4
I1
I3
I4
6.23 5.51 4.90 1.20 1.11 1.03
17.80 13.26 10.64 1.71 1.58 1.47
5.61 4.99 4.45 1.15 1.06 0.99
11.28 10.30 9.38 2.49 2.32 2.17
19.63 17.78 15.90 3.79 3.53 3.32
9.18 8.46 7.78 2.31 2.16 2.03
2.98 2.75 2.55 0.75 0.70 0.66
4.79 4.41 4.09 1.14 1.07 1.01
2.72 2.53 2.34 0.71 0.67 0.62
The lowest (best) values in rows for the ecological cost-effectiveness.
Table 12 Ecological cost-effectiveness ECEN [PLN/Pt]. Constr. material
C1
C3
Climatic zone
I III V I III V
Heat source S1
S2
S3
Thermal insulation material
Thermal insulation material
Thermal insulation material
I1
I3
I4
I1
I3
I4
I1
I3
I4
6.70 5.99 5.35 1.11 1.01 0.92
11.19 9.92 8.79 2.11 1.90 1.73
6.22 5.59 5.02 1.06 0.96 0.88
10.79 9.63 8.58 1.76 1.59 1.45
18.99 16.69 14.67 3.37 3.04 2.76
9.71 8.74 7.85 1.66 1.51 1.37
2.59 2.33 2.08 0.44 0.40 0.36
4.12 3.69 3.29 0.82 0.74 0.68
2.49 2.24 2.01 0.42 0.38 0.35
The lowest (best) values in rows for the ecological cost-effectiveness.
Fig. 4. The ecological values of thermal insulation investment VE_N [Pt/m2] for selected variants, where. type of construction material: C1 e cellular concrete blocks, C3 e ceramic hollow blocks; heat source: S2 e natural gas boiler, S3 e electricity boiler; thermal insulation material: I3 e polyurethane foam, I4 e eco-fibre.
obtained, i.e. the reduction of environmental load due to the analyzed thermal insulation investment. However, the differences between variants are very large, the values depend significantly on all four factors taken into consideration: the climatic zone, the construction material of the wall, heat source used and thermal insulation material. The highest values VE_opt were obtained for the case of: construction material C3 (the smallest thermal resistance),
heat source S3 (the largest environmental load of producing 1 kWh of heat energy) and thermal insulation material I4 (the lowest value of the LCA result expressed in [Pt/m3]). Table 10 summarizes designated ecological values of the thermal insulation investment VE_N, with the thermal transmittance UN ¼ 0.25 W/m2 K and the thickness of thermal insulation dN. Comparing the results from Tables 9 and 10 it can be seen that
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Fig. 5. Ecological cost-effectiveness ECEN [PLN/Pt] for selected variants, where: type of construction material: C1 e cellular concrete blocks, C3 e ceramic hollow blocks; heat source: S2 e natural gas boiler, S3 e electricity boiler; thermal insulation material: I3 e polyurethane foam, I4 e eco-fibre.
wherever Uopt < UN we obtain VE_opt > VE_N. Due to the thermal insulation material the best results were obtained for eco-fibre (I4), as with the insulation thickness dopt. On the basis of ecological values of investment VE_opt and financial costs of thermal insulation Cf_opt, determined from formula (1) for dopt, the environmental cost-effectiveness ECEopt was calculated (see formula (7)). The results are shown in Table 11. Due to the type of thermal insulation material by far the smallest cost (in PLN) to reduce the environmental load by 1 Pt is obtained for eco-fibre (I4). Due to the type of the climatic zone the smallest cost of reducing the load on the environment is obtained in zone V, which is an area with the lowest average annual external and project temperatures. Similarly, the ecological cost-effectiveness ECEN was determined, with the thermal insulation thickness dN (see Table 12). Comparing ECEopt with ECEN for the same variants, sometimes the first value is greater and sometimes the other (yet the differences are not big) because the cost-effectiveness also depends significantly on the financial costs of thermal insulation. As it can be seen in Tables 11 and 12 that the differences in the ecological costeffectiveness between different variants are very large. This effectiveness depends significantly, like the ecological value of the investment, on the climate zone, construction material of the wall, heat source used and thermal insulation material. 6. Discussion It should be noted that the obtained results are to a large extent influenced by the condition of the building before thermal insulation. Both the ecological value of the investment VE and the ecological cost-effectiveness ECE were obtained by far the best when using silicate (C3) as a construction material. This material has definitely the worst thermal properties among the ones under consideration (see Table 2). A significant impact on the results is also exerted by the heating energy demand, which depends on the
climate zone. In zone V, this demand can be even more than 30% higher than in zone I. The best LCA result among the examined thermal insulation materials was obtained for eco-fibre (I4), which is also relatively inexpensive. Consequently, also VE and ECE were obtained the best for this insulation material. Using formula (3), the ecological payback period TE of the thermal insulation investment for all tested variants was also determined. The values in the range 0e6 years were obtained. This means that at the latest after 6 years the increase in the environment load as a result of thermal insulation performance will be eliminated by the reduction of environmental burden during the use phase of the building, due to the reduction in energy consumption to heat the building. For eco-fibre (I4) the payback period TE ¼ 0, because E0 is already positive (the production of eco-fibre reduces the burden on the environment). For other variants, the fastest payback takes place (after one or two years) when using heat source S1 or S3 and insulation material I1 or I2. The latest payback period was obtained for variant S2eI3, TE ¼ 5 with insulation thickness dN and TE ¼ 6 with insulation thickness dopt, both for building B1 and B2. It should be noted that for heat source S2 the best result of the LCA analysis was obtained (see Table 3), and for the insulation material I3 e the worst result of the LCA analysis (see Table 1). At the end, the graph (Fig. 4) summarizes the results for buildings B1 and B2 on the ecological value of thermal insulation investment VE_N (with the thermal transmittance UN ¼ 0.25 W/m2 K). There were selected variants, which obtained the smallest and largest values: (a) C1eS2eI3 in zone I, (b) C1eS3eI4 in zone V, (c) C3eS2eI3 in zone I and (d) C3eS3eI4 in zone V. Despite the large differences in the demand for heat between buildings B1 and B2 (see Tables 5 and 6), the differences in the obtained values VE_N are very small. The situation is similar in the case of VE_opt. As it was previously emphasized, the huge importance on ecological effects of the thermal insulation investment is given by: the condition of the building before thermal insulation, in particular construction material of the wall, heat source used and type of thermal insulation material.
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Fig. 5 summarizes the results for buildings B1 and B2 on the ecological cost-effectiveness of ECEN for the same variants as in Fig. 4. The differences between the buildings are very small. Just as for VE_N the values of this indicator depend primarily on the construction material of the wall, heat source used and type of thermal insulation material.
7. Conclusions The studies were carried out by locating the buildings in different zones in order to illustrate the variation of the size of the heat demand, and hence the impact on the environment. The demand for thermal energy for heating purposes in zone V was obtained by 38.1% higher than in zone I (for the building B1) and by 34.5% (for the building B2) for the variant, in which the external vertical walls were insulated in accordance with the applicable standards (UN ¼ 0.25 W/m2 K). Having the knowledge of the basic variables: location in the climatic zone, the type of heat source, the type of construction material of the wall and the type and thickness of thermal insulation, it is possible, using the method presented in the paper, to determine the ecological cost-effectiveness. It should be emphasized that all these factors have a strong influence on the results. The most favourable values of the ecological cost-effectiveness ECE expressed in [PLN/Pt], were obtained for the construction material of the wall with the worst thermal transmittance (silicate SILKA E), the most ecological thermal insulation material (eco-fibre), the type of heating with the worst result of the LCA analysis (electricity) and the most extreme (cold) climate occurring in Poland e
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climatic zone V. On the other hand, the worst values ECE were obtained for the construction material of the wall with the best thermal transmittance (cellular concrete 500), the insulation material, which was the most expensive and had the worst LCA result (polyurethane PUR), the type of heating with the best result of the LCA analysis (natural gas) and climate zone I. It should also be noted that ecological payback period of thermal insulation investment for the studied variants was obtained in the range 0e6 years, which is at the latest after 6 years, the increase in the burden on the environment as a result of thermal insulation performance will be eliminated by the reduction of environmental load during the use phase of the building, due to the reduction in energy consumption to heat the building. The shortest payback periods were obtained for variants with thermal insulation made of eco-fibre (0 years), as already the production of eco-fibre reduces the burden on the environment. The latest payback periods were obtained for variants with a heat source e natural gas boiler and thermal insulation material e polyurethane PUR (5 or 6 years depending on the thickness of the insulation). The proposed method proved to be very helpful in assessing various options for thermal insulation investments. It can also be used in other places in the world. It allows to take into account both the environmental and economic aspects of the investment. This method could be useful for designers and energy/environmental auditors.
Appendix
Table A1 Description of the analyzed buildings.
2
Usable area pu [m ] Area of external vertical walls p [m2] Building volume [m3] Central heating systems
Ventilation system Heat accumulation efficiency Transport efficiency of the heating medium Efficiency regulation and utilization Computational averaged internal air temperature [ C] Heat gains [W/m2] Building structure
Window and door frames
House I (B1)
House II (B2)
140.20 206.61 376.14 Heating water pumps, thermally insulated pipes run in the wall furrows, in the floor and on the top of the walls; the living areas were designed with panel radiators and in the bathroom e towel rail radiators Natural/gravitational ventilation 97% 97%
144.70 200.26 383.48
98% 20 3.5 The design of a traditional brick, reinforced concrete floors, densely ribbed, wooden stairs, roof of a wooden structure, coverage of metal-tile roofing, mineral plaster provided on walls
The building construction is brick, ceilings e a “TERIVA” type, in the attic e a wooden roof, covering e tile or sheet metal, a roof pitch e 30 , mineral plaster
Window frames with diffusers, with thermal transmittance for the window frames U ¼ 1.3 W/m2 K, the outer door of the thermal transmittance U ¼ 1.8 W/m2 K
Table A2 Design outdoor temperature, average annual outdoor temperature and the coordinates of the cities. Climatic zone
Project outdoor temperature [ C]
Average annual outdoor temperature [ C]
City
Latitude
Longitude
I II III IV V
16 18 20 22 24
7.7 7.9 7.6 6.9 5.5
Szczecin ra Zielona Go Kielce Białystok Suwałki
53.430 N 51.940 N 50.889 N 53.139 N 54.109 N
14.529 E 15.489 E 20.649 E 23.159 E 22.940 E
Source: EN 12831 (2006).
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