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Comparative life cycle assessment of passive and traditional residential buildings’ use with a special focus on energy-related aspects
Energy and Buildings 67 (2013) 635–646
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Comparative life cycle assessment of passive and traditional residential buildings’ use with a special focus on energy-related aspects Anna Lewandowska a,∗ , Andrzej Noskowiak b , Grzegorz Pajchrowski b a b
Faculty of Commodity Science, Poznan University of Economics, Al. Niepodleglosci 10, Poznan 61-875, Poland Wood Technology Institute, ul. Winiarska 1, Poznan 60-654, Poland
a r t i c l e
i n f o
Article history: Received 26 May 2013 Received in revised form 12 August 2013 Accepted 1 September 2013 Keywords: Energy consumption Environmental impact Buildings
a b s t r a c t This article presents the results of the research project financed by the Polish Ministry of Science and Higher Education (N N309 078138) and coordinated by the Wood Technology Institute in Poznan. A key point of this project was LCA study performed for four detached single-family dwellings with a particular emphasis on the use stage. The life-cycle assessment involved various types of activity made within a hundred years of use and related to: operation (energy and water consumption), replacements and repairs, renovations and maintenance, land occupation, waste transport and waste management. Two of the four analyzed buildings met passive house standards and their energy demands in the use stage were several times lower than those of their conventional counterparts. The aim of the studies was to demonstrate whether lower nominal energy consumption is sufficient to get the best results of the environmental impact of passive buildings, or whether a type of energy used to cover the demand also plays an important role. © 2013 Elsevier B.V. All rights reserved.
1. Introduction Sustainable construction is a response to the growing awareness of the negative impact of buildings on the environment as well as the health and lives of people [1]. In practice, different terms (ecological, green, energy-efficient) are used to describe the environmentally friendly construction. The sources of the concept can be found in a report of the World Commission on Environment and Development and the birth of the idea of sustainable development. According to it, sustainable construction is one that meets the needs of the present without compromising the ability of future generations to meet their own needs [2]. Sustainable construction has strong legislative justification that provides a backdrop to undertake such initiatives. Pursuant to the EU Directive 2002/91/EC, from January 2009, all real estate buildings newly put into use or marketed in Poland have to undergo Energy Performance Certification. In accordance with Directive 2010/31/EU, the EU Member States were obliged to change their national regulations on the energy performance of buildings by July 2012 to reduce energy consumption in the building sector by 20%. In addition, each constructed building will have to meet certain standards for minimum energy performance after July 2013 [1]. In the longer term, in accordance
∗ Corresponding author. Tel.: +48 618543121. E-mail address: [email protected] (A. Lewandowska). 0378-7788/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.enbuild.2013.09.002
with Directive 2010/31/EU, all new buildings will have to have a near-zero energy consumption after January 2021 (public buildings after 2018). The construction, as highly energy intensive sector, is strongly related to national energy system. In Poland the most strategic document in this area is Energy Policy of Poland until 2030 [3] and especially Appendix 2 [4]. The following targets for Polish energy system are assumed to achieve in coming fifteen years: an improvement of energetic effectiveness, an increase of security of fuel and energy supplies, a diversification of the structure of electrical energy production, including the introduction of nuclear energy, a development of use of renewable energy sources (including biofuels), a development of competitive markets of fuels and energy and a limitation of power energy effects upon the environment. A regulation of the Minister of Environment as of 20 December 2005 relating to emission standards for fuel combustion installations [5] and respective EU provisions [6–8] are also important documents from energy consuming long life buildings’ point of view. Due to the significant environmental impact of the construction sector, different measures are taken to make environmental assessment of construction activity. Due to the very long operation periods, versatility, high structural complexity and material comprehensiveness, buildings are a complex and unique objects of ecological studies. Life cycle assessment (LCA) [9,10] is one of the tools for the environmental assessment of solutions in the construction industry. LCA studies can be conducted for residential
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Fig. 1. LCA studies in the construction industry – objects and scopes. Source: [26].
or non-residential buildings [11–16] as well as civil and hydraulic engineering facilities, although these are less common [17–20]. As for the LCA scope, the literature [19,21–25] suggests analysing: Building Materials (BM), Component Combination (CC) and The Whole Process of the Construction (WPC). As a result, the LCA scope may be varied and refer to different buildings (Fig. 1). Full-scope LCA provides a full picture of environmental impacts and their sources, taking into account the whole life cycle of buildings. With this type of research, it is possible to define key issues such as: building materials and the related manufacturing technology, the use of a building, or perhaps issues related to waste management, transport or construction processes. Most studies have shown that the main environmental problem lies in the use stage energy consumption of buildings as energy-consuming facilities with a life cycle of at least decades. Thus, the tightening of legislation on building energy performance standards has profound environmental reasons. Sustainable construction is a response to changes taking place in legislation and awareness. A particular
example of sustainable building is passive construction, called super energy-saving because of the extremely low heat demand of the buildings (air heating in the ventilation system is often sufficient as the only heat source) [27]. The heat demand of passive buildings can be several times lower than that of their conventional counterparts. However, getting energy levels characteristic for passive buildings (annual heat demand of a building cannot exceed 15 kWh/m2 per year) is possible by increasing the consumption of building materials, especially insulation. Therefore, improvement is achieved in one life cycle stage, but at the cost of a deterioration in the others, because an increased use of building materials is not only related to a higher impact of their production, but also increased transport activity (both in the transport of new materials and waste) and the need for more waste management. LCAs of buildings can demonstrate whether such measures are environmentally “profitable” and whether the benefits of improved energy performance outweigh the negative impacts occurring in the other stages.
A. Lewandowska et al. / Energy and Buildings 67 (2013) 635–646
This article presents the results of the LCA studies of four equivalent buildings, with a particular emphasis on the use stage. The environmental assessment involved different (energy and nonenergy-related) environmental interventions made during one hundred years of use of detached single-family dwellings. It was assumed that two of the four buildings met passive house standards and their energy demands were several times lower than those of their conventional counterparts. The aim of the studies was to demonstrate whether lower nominal energy consumption was sufficient to get the best results of the environmental impact of passive houses, or whether a type of energy used to cover that demand also played an important role. The studies assumed that the passive buildings, showing 3.6 times lower demand for heat, would be heated up with electric heaters, while the conventional buildings would be equipped with a gas heating system. In addition to the energy-related aspects, the analysis also involved other use-related issues: replacements and repairs, renovations and maintenance, land occupation, transport, water consumption, waste management and sewage treatment (generated throughout the entire use stage). The type and quantity of the materials used for replacement and repair depended on the structure of building materials and their manufacturing technologies. 2. A life cycle perspective The objects studied were four model one-family residential dwellings for a 4-person family with a usable area of 98.04 m2 . These buildings differed in material structure, manufacturing technology and energy performance standard. With regard to the first two criteria, the analyzed objects were two masonry and two wooden buildings. A wooden building should be understood as a material structure and manufacturing technology which maximizes the use of wood wherever it is technically and operationally justified. Therefore, it was assumed that wood and wood-based materials were used in the roofs of the wooden houses (rafter framing – coniferous timber, roofing material – wooden shingle), facade (board), floor (floor board), interior window sills and walls (OSB, MDF, HDF, cellulose). As for the masonry buildings, the use of wood was assumed only in rafter framing (coniferous timber). As for energy standards, two of the analyzed buildings met the requirements of passive houses, while the others were traditional buildings. Therefore, the studies involved: • • • •
Traditional masonry building (A1), Passive masonry building (A2), Traditional wooden building (B1), Passive wooden building (B2).
All of the buildings were single-storey houses with the following function program: entrance hall (lobby), toilet, living room with dining area, kitchen, double bedroom, two single rooms, bathroom and laundry room. An architectural firm prepared a separate architectural design for each of the buildings. The use of materials, performance parameters, equipment installation and energy consumption were calculated individually for each of the buildings, while for the options A2 and B2 it was done taking into account the requirements for passive buildings [27,28]. The buildings were located relative to the directions of the world in such a way as to maximize the effect of solar radiation (large windows in the south wall), which is particularly important for passive houses. The assumed location of the buildings is Poznan, placed in western Poland. The WPC studies involved the entire four buildings which were analyzed in the context of their full life cycle, including the following stages: production of building materials (stage 1), transport
637
of building materials to the construction site (stage 2), construction (stage 3), use (stage 4), demolition (stage 5), demolition waste transport to the place of its final disposal (stage 6) and the final demolition waste disposal (stage 7). The buildings are multifunctional objects fit for fulfilling residential, protective, hygienic, aesthetic and construction functions, what can make an inclusion all of them to the functional unit problematic. The main functions taken into account in the studies were the residential and protective functions, based on which the functional unit of the studies was defined as: ensuring 98.04 m2 of habitable floor area for residential use within 100 years and protecting its users and objects against harmful effects of external factors during the period. Since the analyzed buildings have the same lifetime, the reference flow in each case is one building A1, A2, B1 or B2. Table 1 shows the general mass inputs and outputs and the final mass balance for the life cycles of the analyzed buildings. In order to make a balance, all inventory data, excluding electricity and heat, were converted to mass units. Natural gas consumption in the traditional buildings in the use stage was also excluded from the mass balance, because the inventory data related to gas combustion was taken from the ecoinvent database [29] where were expressed in energy units. If the input gas consumption had been expressed as mass, this would have required adding air to the inputs and emissions and waste to the outputs. As these data had already been included in the ecoinvent’s inventory table, it was assumed that the balance had been already made by the authors of the data and subject to verification in the ecoinvent validation process. The balance also excluded transport and demolition stages as they had no mass inventory data. The results in Table 1 show that the main mass flows in the life cycle of the analyzed buildings take place in the use stage, and cover over 98% of the total balance results. This applies to all the analyzed buildings, regardless of the manufacturing technology, material structure and energy performance. This is due to the fact that the balance for the use stage includes the mass flows of materials (inputs) and waste (outputs) generated over the 100-year time horizon, and arising out of repairs, replacements, renovations and maintenance, as well as water consumption and sewage production. 2.1. Stage 4 – use of the buildings – life cycle inventory In the present studies the building use stage was divided into seven areas: operation (energy and water consumption), replacements and repairs, renovations and maintenance, land occupation, waste transport and waste management. The scope of each area is characterized in Table 2. In addition, the following assumptions were made: • The time of use of a building is 100 years, • The amount of sewage is equal to water consumption, • Walls are painted with a frequency shown in Table 6, while the earlier layers of paint are not removed before the next painting. For this reason, the mass inputs of paint for renovations and maintenance in the use stage do not have their equivalents in the outputs, and appear only in the final demolition waste management (hence the difference in the mass inputs and outputs for stage 4 in the balance), • A similar assumption was applied to the painting of wooden doors and windows, with the difference that, in contrast to the walls, they are subject to replacements, whereas “accumulated” paint layers “leave” the use stage together with these elements. Those that relate to the last replacement before demolition appear in the outputs associated with the final demolition waste management, • In order to calculate the environmental impact of electricity consumption, inventory data representative for Poland are used as baseline scenario and taken from ecoinvent database v2.2.
13 254.37
Basic data and assumptions about the different areas of use are included in Tables 2–6. The water consumption was calculated using the guidelines included in the regulation of the Minister of Construction as of 14 January 2002 relating to determination of mean water consumption standards [30] and national statistics published by the Polish Central Statistical Office [31]. The energy consumption was calculated using the methodology of buildings energy certification and the technical data included in architectural projects. The calculations were carried out for assumed buildings’ location on the basis of meteorological data taken from the weather station in Poznan (52◦ 25 N, 16◦ 51 E). The annual values of heating degree day (HDD) and cooling degree day (CDD) specific for Poznan are: HDD = 3677 and CDD =120 (base temperature: 18 ◦ C) (). From life cycle inventory’s point of view, a short comment concerning data quality is needed. The uncertainty analyses showed that there was no significant difference in the quality of the data and the uncertainty of results between the buildings. Primary data were used for the same life cycle stages in all cases, and so were the secondary data (mainly from databases and literature): if used, they were consistent with similar areas in the life cycle of each building. 2.2. Stage 4 – use of the buildings – life cycle impact assessment
13 412.92 100.00 Total
13 385.41
13 385.41
100.00
13 412.92
100.00
100.00
13 310.17
100.00
13 310.17
100.00
100.00
13 254.37
100.00
According to this scenario the following shares of energy carries are assumed: hard coal 55.4%, brown coal 36.3%, natural gas 3.3%, crude oil products 1.6%, renewable energy 2.1%, pumped storage energy 1.1%, nuclear energy and waste energy 0.0%. In a case of gas consumption, ecoinvent data representative for Europe are used and a heat production based on natural gas, combusted at boiler modulating <100 kW assumed. This inventory module includes fuel input from low pressure (CH) network, infrastructure, emissions, and electricity needed for operation [29], • In the baseline scenario the above technological mix of production energy in Poland was assumed as static over the 100 years lifetime, but some additional scenarios are compared and presented in Section 3.
Source: [26].
0.00 1.41 13 160.18 92.77
Mg %
0.69 0.00 99.30 0.00 91.95 0.58 13 161.81 0.00
Mg %
0.00 0.01 98.85 1.14 0.00 1.40 13 156.83 151.95
Mg %
1.13 0.01 98.86 0.00 150.99 0.69 13 158.49 0.00
Mg %
0.00 0.04 98.15 1.81 0.00 5.25 13 164.25 243.42
Mg %
1.82 0.02 98.16 0.00 244.28 2.63 13 166.00 0.00
Mg %
0.00 0.03 98.33 1.64 0.00 3.84 13 162.48 219.08
Mg % Mg
1.63 0.02 98.35 0.00
Outputs Inputs Outputs Inputs Outputs Inputs
217.99 3.19 13 164.23 0.00 Stage 1 – production of building materials Stage 3 – building site (construction process) Stage 4 – use (100 years) Stage 7 – final disposal of demolition waste
Outputs Inputs
B2 – passive wooden building B1 – traditional wooden building A2 – passive, masonry building A1 – traditional, masonry building Life cycle stages
Table 1 Mass balance of the life cycles of the four buildings.
0.00 0.01 99.29 0.70
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%
638
LCIA studies were conducted using SimaPro Analyst 7.3 and Impact 2002+ method, representing a combination of four LCIA methods: IMPACT 2002+ [32], Eco-indicator 99/E [33], CML [34] and the IPCC. At the most cumulative level, the environmental impact is an ecoindicator value expressed in points [Pt]. A cumulative ecoindicator result can be “broken down” into smaller components: weighted damage and impact category indicator results. Since Impact 2002+ is a combined method, the same damage and impact categories can be further analyzed at more desegregated levels: normalization and characterization (midpoint level). This article presents Eco-indicator results [Pt] and weighted impact category indicator results [Pt]. The higher the positive indicator, the greater the negative impact on the environment. A negative indicator is interpreted as an environmental benefit. Fig. 2 presents the environmental impacts of the life cycles of the analyzed buildings divided into different stages. As can be seen, the passive masonry building A2 has the highest impact (270.6 Pt), while the traditional wooden house B1 has the best result (230.7 Pt). The use stage had the greatest environmental impact for all the buildings, regardless of their material structures, manufacturing technologies and energy standards, but in the case of this stage the results had to be related to the energy performance of the buildings, since both traditional buildings showed lower environmental indicators than their passive counterparts. The environmental impact of the 100-year use of the house A1 was 229.5 Pt, A2 – 249.0 Pt, B1 – 223.2 Pt and B2 – 245.1 Pt. As for the masonry houses, stage 4 accounted for 92% of the cradle-to grave impact, and for the wooden houses, it was more than 95% (black in Fig. 2). This difference resulted from the material structure of the buildings and
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Table 2 Description of the areas included in Stage 4 – use of the buildings. Areas of use
Inventory data used in the study
Sources of assumptions and data
Operation
• Energy consumption for heating • Energy consumption for ventilation • Energy consumption in equipment • Energy consumption for cooling • Energy consumption for hot water preparation • Energy consumption for built-in lighting
• Data on heating, ventilation, cooling, hot water preparation and use based on architectural projects and energy certificates • Water and energy consumption for living purposes based on the Regulation of the Minister of Infrastructure of 14 January 2002 on the definition of the average water consumption standards and the Statistical Yearbook 2011
Replacements and repairs
• Consumption of building materials for replacement of selected components/building modules (Table 5) • Transport of building materials subject to replacements
• Replacement and repair frequency based on the literature and our own experience (as shown in Table 5)
Renovations and maintenance
• Consumption of building materials for renovation of selected elements/building modules (Table 6)
• Renovation frequency based on the literature and our own experience (as shown in Table 6)
Land occupation
• Land occupation
• Land occupation based on the building plot area and the time of use
Transport of building materials
• Transport of construction materials used for renovation and maintenance
• Cargo weight based on the use of construction materials in the individual components/modules of the house (without losses) • Distances calculated using vehicle route planning software • Information on the means of transport used to carry different types of building materials taken from the literature
Waste transport
• Transport of waste (after replacements and repairs, renovations and maintenance)
• Cargo weight based on the use of construction materials in the individual components/modules of a house (no losses) • Distances calculated using vehicle route planning software • Information on the means of transport used to carry different types of building materials taken from the literature
Waste management
• Sewage treatment and waste management (resulting from replacements and repairs, and renovations and maintenance)
• Type and amount of waste based on the use of building materials in the individual components/modules of a house subject to replacement • The amount of sewage generated based on water consumption
Source: [26].
lower environmental impact of stage 1 (production of construction materials) of the wooden houses B1 and B2 where a higher proportion of wood generated an environmental benefit in terms of climate change and Eco-indicator. The results obtained for the use of the buildings were divided into different areas in order to identify the source largely responsible for creating the negative impact. The data in Table 7 and Fig. 3 show that there is one major source of impact, i.e. operation which is responsible for creating 86–89% of impact throughout the use stage. Replacements and repairs take the second place (4–6%), and they are followed by land occupation (approximately 3%) and waste management (about 3%). The studies show that, in principle, there is one major source of the negative impact in the operation stage i.e. energy consumption. At the same time, the passive houses had worse results in this
regard (Table 8). The negative environmental impact generated by electricity consumption in the traditional houses was 66.4 Pt, and by heat energy consumption – 130 Pt. The former is nearly 30% of the total impact exerted in stage 4 and the latter – almost 60%. The situation is similar in the case of the passive houses, except that they use only electricity, the environmental impact of which is 215 Pt, which is in itself almost 90% of the indicator for the use stage. 3. Discussion and scenario analysis The total energy (gas and electricity) consumption (expressed in energy values, kWh) in the traditional buildings A1 and B1 is almost 3.6 times higher than the consumption in the passive buildings A2 and B2. However, the electrical energy consumption in the
Table 3 Annual consumption of utilities during the operation of the buildings. Operation A2 passive masonry building
B1 traditional wooden building
B2 passive wooden building
Unit
Inventory element
A1 traditional masonry building Consumption
Electricity – rtv and household equipment Electricity – lighting Electricity – heating Electricity – hot tap water Electricity – ventilation Heat (natural gas) – heating Heat (natural gas) – hot tap water Electricity (ancillary) Hot water (55 ◦ C) Cold water Sewage
1 600.0 350.0 – – – 15 637.7 6 584.5 130.8 45 990.0 85 410.0 131 400.0
1 600.0 350.0 1 429.5 3 010.9 343.5 – – – 45 990.0 85 410.0 131 400.0
1 600.0 350.0 – – – 15 484.7 6 584.5 130.8 45 990.0 85 410.0 131 400.0
1 600.0 350.0 1 470.4 3 010.9 343.5 – – – 45 990.0 85 410.0 131 400.0
kWh/year kWh/year kWh/year kWh/year kWh/year kWh/year kWh/year kWh/year L/year L/year L/year
Building
Source: [26,30,31].
640
A. Lewandowska et al. / Energy and Buildings 67 (2013) 635–646
Table 4 Energy consumption in the buildings A1, A2, B1 and B2 during the 100 years of use. Inventory element
A1 traditional masonry building
B1 traditional wooden building
Unit
Comment
Electricity Electricity Natural gas Natural gas Electricity
160,000 35,000 1,563,769 658,446 13,076
160,000 35,000 1,548,468 658,446 13,076
kWh kWh kWh kWh kWh
Rtv and household equipment Lighting Heating Hot water (55 ◦ C) Electricity (ancillary)
Total As electricity Electricity
2,430,291 8.6 160,000
2,414,990 8.6 160,000
kWh % kWh
Inventory element
A2 passive masonry building
B2 passive wooden building
Unit
Comment
Electricity Electricity Electricity Electricity Electricity
160,000 35,000 142,950 301,091 34,353
160,000 35,000 147,037 301,091 34,353
kWh kWh kWh kWh kWh
Rtv and household equipment Lighting Heating Hot water (55 ◦ C) Ventilation
Total As electricity As natural gas
673,394 100.00 00.00
677,481 100.00 00.00
kWh % %
Source: [26,30,31].
Table 5 Durability of components subject to replacements and repairs for the four technological variants of the analyzed buildings. Replacements and repairs B1 traditional wooden building
Building
A1 traditional masonry building
A2 passive masonry building
Inventory element
Durability [years]
Number of replacements [times]
Durability [years]
Number of replacements [times]
Durability [years]
Number of replacements [times]
Durability [years]
Number of replacements [times]
Constructional elements Windows Internal doors External doors Wood flooring Gas heating system (without boiler) Gas boiler Ceramic tiles (floor and walls) Power supply system Water supply system Sewage system Ventilation system Roof gutter system Roof covering Rafter framing (selected elements) Roof insulation Ceiling insulation External wall insulation Internal walls insulation Fac¸ade
100 25 30 30 – 50 20 20 50 50 50 – 50 50 50 50 50 – – –
0 3 3 3 – 1 4 4 1 1 1 – 1 1 1 1 1 – – –
100 25 30 30 – – – 20 50 50 50 50 50 50 50 50 50 50 – –
0 3 3 3 – – – 4 1 1 1 1 1 1 1 1 1 1 – –
100 25 30 30 50 50 20 20 50 50 50 – 50 50 50 50 50 50 50 50
0 3 3 3 1 1 4 4 1 1 1 – 1 1 1 1 1 1 1 1
100 25 30 30 50 – – 20 50 50 50 50 50 50 50 50 50 50 50 50
0 3 3 3 1 – – 4 1 1 1 1 1 1 1 1 1 1 1 1
B2 passive wooden building
Source: [26]. Source: [26]
Table 6 Durability of components subject to renovations and maintenance for the four technological variants of the analyzed building. Renovations and maintenance Building
A1 traditional masonry building
A2 passive masonry building
Inventory element
Durability [years]
Number of replacements [times]
Durability [years]
Number of replacements [times]
Durability [years]
Number of replacements [times]
Durability [years]
Number of replacements [times]
Internal wall painting External wall (fac¸ade) painting External door painting Internal door painting Wood window painting Wood floor varnishing
5 25 10 15 -
19 3 6 3 -
5 25 10 15 -
19 3 6 3 -
5 25 10 15 5 25
19 2 6 3 19 2
5 25 10 15 5 25
19 2 6 3 19 2
Source: [26].
B1 traditional wooden building
B2 passive wooden building
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B2 - PASSIVE, WOODEN BUILDING
B1 - TRADITIONAL, WOODEN BUILDING
A2 - PASSIVE, MASONRY BUIDLING
A1 TRADITIONAL, MASONRY BUIDLING
-50
0
50
100
150
200
250
300
Environmental impact [Pt] STAGE 1 - PRODUCTION OF BUIDLING MATERIALS
STAGE 2 - TRANSPORT OF BUILDING MATERIALS
STAGE 3 - BUIDLDING SITE (CONSTRUCTION PROCESS)
STAGE 4 - USE (100 YEARS)
ETAP 5 - DEMOLITION
ETAP 6 - TRANSPORT OF WASTE AFTER DEMOLITION
STAGE 7 - FINAL DISPOSAL OF WASTE AFTER DEMOLITION
Fig. 2. Eco-indicator results for particular life cycle stages of the analyzed buildings (baseline scenario) [Pt]. Source: [26].
Table 7 Contribution of different areas of use to the negative environmental impact. Areas of use
A1 traditional, masonry building
A2 passive, masonry building
B1 traditional wooden building
B2 passive wooden building
[Pt]
[Pt]
[Pt]
Environmental impact [Pt] Land occupation Operation Replacements and repairs Renovations and maintenance Transport of building materials Transport of waste Final disposal of waste
7.0 198.5 13.5 1.7 1.8 0.02 7.0
Total
229.5
[%] 3.0 86.5 5.9 0.7 0.8 0.009 3.0 100.0
7.0 217.0 15.7 1.7 1.7 0.02 5.2 249.0
[%] 2.8 87.1 6.3 0.7 0.7 0.008 2.1 100.0
[%]
7.0 198.0 15.8 1.7 0.8 0.03 6.1
3.1 86.3 6.9 0.7 0.3 0.01 2.7
223.2
100.0
[%]
7.0 218.0 9.8 1.7 0.8 0.03 7.2
2.9 89.1 4.0 0.7 0.3 0.0 2.9
245.1
100.0
Source: [26].
Environmental impact [Pt]
traditional buildings accounts for only about 31% of energy consumption in the passive buildings. The reasons for the differences in the results of environmental indicators should be sought in different environmental burden of electricity and heat production from natural gas. According to the technological scenario for Poland the production of 1 kWh of electricity has an environmental impact of 0.000321 Pt, and the acquisition of 1 kWh of heat energy from natural gas has an environmental impact of 0.0000603 Pt. Thus, 1 kWh of electricity is 5.3 times worse environmentally than the equivalent amount of energy acquired directly from natural gas combustion. In both cases, the impact categories largely affected by
the negative effects are: respiratory disorders/inorganic compounds, global warming and non-renewable energy, which is a typical picture of the environmental impact of combustion processes based on non-renewable energy sources (Table 9). From the perspective of the environmental impact, the use of the analyzed buildings is dominated by energy issues, so the structure of the environmental impact of this stage (but also the whole life cycle) corresponds to the image of the typical effect of energy production (Fig. 4). It is dominated by three impact categories. Two output related categories: respiratory disorders resulting from emissions of inorganic compounds (mainly carbon dioxide,
250 225 200 175 150 125 100 75 50 25 0
A1
Land occupation Renov ations and maintenance Renovations conservations Final disposal of waste
A2
B1
Operation Transport of building materials
B2
Replacements and repairs Transport of waste
Fig. 3. Eco-indicator results for particular areas of stage 4–100 years of buildings’ use (baseline scenario) [Pt]. Source: [26].
231.8
94.6
0.2 0.5 0.3
94.8
0.6
211.7
0.5 1.1 0.7
94.4
1.7
235.1
Steel radiators
0.6 1.3 1.4 3.5
Windows
• Scenario DK – energy demand in the use stage of all the four buildings is covered by electricity produced in accordance with the current mix of energy production in Denmark [29], • Scenario DE – energy demand in the use stage of all the four buildings is covered by electricity produced in accordance with the current mix of energy production in Germany [29], • Scenario PL – energy demand in the use stage of all the four buildings is covered by electricity produced in accordance with the structure of energy production assumed for Poland in the following years: - Scenario PL 2020 – the energy mix for 2020 year assumed according to Energy Policy of Poland until 2030 [3,4] where the increase in share of renewable energy (19.3%) and the initiation of nuclear energy production (6.7%) are the most significant changes in comparison to baseline scenario, - Scenario PL 2025 – the energy mix for 2025 year assumed according to Energy Policy of Poland until 2030 [3,4] where increased share of nuclear energy (11.7%) and decreased consumption of coal are the most significant changes in comparison to previous scenarios, - Scenario PL 2030 – the energy mix for 2030 year assumed according to Energy Policy of Poland until 2030 [3,4] where increased share of nuclear energy up to 15.7% is the most important change in comparison to previous scenarios, - Scenario PL 2050 – the energy mix for 2050 year assumed according to Energy mix for Poland – scenarios 2050 [35] where really high share of nuclear energy (23%) and very low contribution of coal (13.2% hard coal and 7.8% brown coal) are the most important modifications in comparison to previous scenarios. The electricity production mix 2050 prepared by Institute for Structural Research (IBS) was selected for calculations (Table 10).
0.6
94.2
1.3
216.3 Source: [26].
Fig. 5 and Table 11 presented below show the results of the cumulative eco-indicator for the adopted scenarios in comparison to baseline scenario. As can be seen, the indicators for the passive houses clearly decrease and the ranking of the buildings varies substantially. The following observations can be made:
Total
Replacements and repairs
1.5 3.5
Ceramic tiles/bathroom Electric cables Replacements and repairs
Replacements and repairs
1.0 2.3 Windows
Ceramic tiles/bathroom Electric cables
1.0 2.5 1.4 3.1 Ceramic tiles/floor Replacements and repairs
nitrogen oxides, sulfur oxides and particulate matter) to atmosphere and climate change (mainly due to emissions of carbon dioxide, and methane to a much lesser extent). The third inputrelated impact category is the depletion of non-renewable energy resources. As shown hereinabove, the use stage, and in principle, energy consumption in this stage, turned out to be the main source of the negative environmental impact during the life cycle of all the analyzed buildings. The main issue in the case of the passive houses was the fact that their energy demands were fully satisfied with electricity generated in accordance with the structure of energy production typical of Poland. And even the fact that the overall energy demands of these buildings were several times lower compared to those of the conventional buildings did not wipe out this difference. It can therefore be concluded that not only the quantity but also a type of energy used plays a critical role. It was therefore decided to make a scenario analysis and conduct analogous LCIA studies for the buildings, but under slightly modified assumptions. Due to the fact that the passive construction is especially popular in Germany and Scandinavia, the following three scenarios were adopted (for all three scenarios the same energy consumption values during 100 years are assumed as in the baseline scenario presented in chapter 2):
Cellulose
0.6 1.5
1.6 3.5
3.7 1.2 9.6 3.1 28.9 4.1 Operation Operation
66.6 9.6
Windows
86.3 56.8 130.4
Sewage treatment Ceramic tiles/floor
%
215.0
% Pt
Operation
Heat energy from natural gas Electricity Sewage treatment
Electricity
Pt
Ceramic tiles/bathroom Electric cables
29.7 4.2 66.4 9.6
Windows
0.7 1.7
3.9 1.4 9.6 3.5
58.0
Sewage treatment Ceramic tiles/bathroom Electric cables
%
87.7 215.0
Pt %
129.5
Heat energy from natural gas Electricity Sewage treatment
Pt
Electricity
Inventory point Eco-indicator result
B1 traditional wooden building
Inventory point Eco-indicator result
A2 passive masonry building
Inventory point Eco-indicator result
A1 traditional, masonry building
Inventory point
Areas of use
Table 8 Inventory data for Stage 4 (use) primarily responsible for creating the negative environmental impact.
Eco-indicator result
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B2 passive wooden building
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• All the additional scenarios give lower environmental impact than baseline scenario, regardless of the type of the building. The passive houses have the best results in the scenarios where electricity demand is covered in accordance with the German
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Table 9 Environmental impact of 1 kWh of electricity and heat from natural gas for the three selected impact categories. Impact category
Weighted impact category indicator result
Electricity (energy mix in poland) Respiratory inorganics
Characterized impact category result
0.0000925
Pt
Global warming Non renewable energy
0.000115 0.0000906
Pt Pt
Heat energy from natural gas Respiratory inorganics
0.00000331
Pt
0.0000335
kg PM 2.5 equiv.
Global warming
0.0000246
Pt
0.243
kg CO2 equiv.
Non renewable energy
0.0000308
Pt
4.68
MJ primary
0.000938
1.14 13.8
Environmental intervention
kg PM 2.5 equiv.
NOx – 26% (1.92 g) PM 2.5 – 31.7% (297 mg) SOx – 42.2% (5.07 g) CO2 – 97.8% (1 119.78 g) Brown coal – 35.1% (488 g) Hard coal – 55.8% (402 g) Natural gas – 3.65% (12.49 dm3 )
kg CO2 equiv. MJ primary
NOx – 57.7% (152 mg) PM 2.5–13.5% (4.52 mg) SOx – 28.7% (123 mg) CO2 – 96.6% (235 g) Methane – 3.13% (1.09 g) Natural gas – 96.8% (112 dm3 )
Source: [26].
Fig. 4. The weighted impact category indicator results for stage 4–100 years of buildings’ use (baseline scenario) [Pt]. Source: [26].
Table 10 Technological mix of electricity production in Poland in baseline scenario and selected years (2020, 2025, 2030 and 2050) [%]. Energy carriers Hard coal Brown coal Natural gas Crude oil products Nuclear energy Renewable energy Including: water energy Including: wind energy Including: biomass Including: biogas Including: solar energy Including: geothermal energy Pumped-storage energy Waste In total Source: [3,4,26,29,35]. a Not included in the scenario.
Baseline scenario (%)
Scenario PL 2020 (%)
Scenario PL 2025 (%)
Scenario PL 2030 (%)
55.4 36.3 3.3 1.6 0.0 2.2 1.5 0.1 0.5 0.1 0.0 0.0 1.1 0.0
40.2 25.6 5.4 1.8 6.7 19.3 1.0 4.4 10.1 3.7 0.0 0.0 0.6 0.4
32.4 26.8 6.3 1.6 11.7 20.2 0.9 5.0 9.3 5.1 0.0 0.0 0.6 0.4
35.6 21.0 6.6 1.5 15.7 18.8 0.8 4.6 8.5 4.9 0.0 0.0 0.5 0.3
100.0
100.0
100.0
100.0
Scenario PL 2050 (%) 13.2 7.8 6.0 0.0a 23.0 50.0 4.0 30.0 8.0 0.0 6.0 2.0 0.0a 0.0a 100.0
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Environmental impact [Pt]
300 250 200 150 100 50 0 Baseline scenario
Scenario DE
Scenario DK
A1
Scenario PL 2020
A2
B1
Scenario PL 2025
Scenario PL 2030
Scenario PL 2050
B2
Fig. 5. Environmental impact the whole life cycle of the buildings A1, A2, B1, B2 – electricity in accordance with different technological mix scenarios [Pt].
(Scenario GE) and Danish (Scenario DK) systems and with Polish situation in 2050 year (Scenario PL 2050). The ecoindicator values for these three scenarios decreased from 34.7% (A2, scenario DE) to even 49.8% (B2, scenario PL 2050), in comparison to baseline scenario. The relationships between LCIA results for all analyzed buildings are similar in these three scenarios what resulted from the fact that in 2050 year the Polish energy mix is assumed to reach the structure corresponding to Western countries’ electricity production, • According to Polish scenario in 2020 year the conventional houses are still better, but the superiority is minimal. While the difference between ecoindicator results was 21.5 Pt (A2–A1) and 26.2 Pt (B2–B1) in the baseline scenario, in 2020 year it reduced to 0.3 Pt and 5.0 Pt, respectively. It can be stated than in 2020 year
is that time where the environmental impact of buildings A1 and A2 is equalized. The year for equalizing the results of B1 and B2 is about 2023, since in 2025 the environmental impact of passive house B2 is lower (B1 = 218.3 Pt, B2 = 215.6 Pt), • The lowest indicator result was recorded for the wooden passive house B2. In this case, the reduction in the energy-related environmental burden is enhanced by the positive image of impacts of wood and wood-based building materials. Declines in the indicators can be explained by differences in the environmental burden of energy production in the analyzed countries. According to baseline scenario the production of 1 kWh of electricity in Poland has an environmental impact of 0.00032 Pt, while in Germany – 0.00018 Pt, and in Denmark – 0.00016 Pt.
Table 11 Environmental impact the whole life cycle of the buildings under the assumption that electricity consumed in the use stage is produced according to different electricity mix scenarios. A1 traditional masonry building
A2 passive masonry building
B1 traditional wooden building
B2 passive wooden building
Electricity production according to the current polish energy system (baseline scenario) 249.1 270.6 Eco-indicator result [Pt]
230.9
257.1
Electricity production according to the danish energy system (scenario DK) 215.8 Eco-indicator result [Pt] ↓ 33.3 Change [Pt] (in relation to baseline scenario) ↓ 13.4 Change [%] (in relation to baseline scenario)
162.7 ↓ 107.9 ↓ 39.9
197.5 ↓ 33.4 ↓ 14.4
148.5 ↓ 108.6 ↓ 42.2
176.7 ↓ 93.9 ↓ 34.7
201.8 ↓ 29.1 ↓ 12.6
162.6 ↓ 94.5 ↓ 36.8
Electricity production according to the polish energy system in 2020 year (scenario PL 2020) Eco-indicator result [Pt] 239.7 240.0 Change [Pt] (in relation to baseline scenario) ↓ 9.4 ↓ 30.6 ↓ 3.8 ↓ 12.3 Change [%] (in relation to baseline scenario)
221.3 ↓ 9.6 ↓ 3.9
226.2 ↓ 30.9 ↓ 12.4
Electricity production according to the polish energy system in 2025 year (scenario PL 2025) Eco-indicator result [Pt] 236.4 229.4 ↓ 12.7 ↓ 41.2 Change [Pt] (in relation to baseline scenario) ↓ 5.1 ↓ 16.5 Change [%] (in relation to baseline scenario)
218.0 ↓ 12.9 ↓ 5.2
215.6 ↓ 41.5 ↓ 16.6
Electricity production according to the polish energy system in 2030 year (scenario PL 2030) 235.3 226.0 Eco-indicator result [Pt] ↓ 13.8 ↓ 44.6 Change [Pt] (in relation to baseline scenario) ↓ 17.9 ↓ 5.5 Change [%] (in relation to baseline scenario)
216.9 ↓ 14.0 ↓ 5.6
212.2 ↓ 44.9 ↓ 18.0
Electricity production according to the polish energy system in 2050 year (scenario PL 2050) 211.0 147.3 Eco-indicator result [Pt] ↓ 38.1 ↓ 123.3 Change [Pt] (in relation to baseline scenario) ↓ 15.3 ↓ 49.5 Change [%] (in relation to baseline scenario)
192.6 ↓ 38.3 ↓ 15.4
133.0 ↓ 124.1 ↓ 49.8
Electricity production according to the german energy system (scenario DE) Eco-indicator result [Pt] 220.1 ↓ 29.0 Change [Pt] (in relation to baseline scenario) ↓ 11.7 Change [%] (in relation to baseline scenario)
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Therefore, only half of the impact can be explained by a smaller share of coal (47.6% in Germany, 47.9% in Denmark, while 91.7% in Poland), a higher share of gas (11.4% in Germany, 23.5% in Denmark and 3.3% in Poland) and above all a higher share of RES (10.5% in Germany, 14.1% in Denmark and 3.2% in Poland) in the energy systems of Germany and Denmark, compared to baseline Polish scenario. The contribution of nuclear energy is next strongly important element. The lower environmental impact of all additional scenarios directly resulted from the fact that part of electricity was assumed to be produced in nuclear power plants. In baseline scenario (corresponding to current situation in Poland) the share of nuclear energy is assumed as zero. According to scenario PL 2050 all energy from coal and natural gas should be produced using Carbon Capture and Storage (CCS) technology. Because of lack of appropriate inventory data, the fact of CCS technology use was not included in the calculations. It is highly probable that this kind of inclusion would give even more reduction of ecoindicator results for the passive houses, especially in relation to clime change impact category.
4. Conclusions The studies show that the main source of the negative environmental impact in the life cycles of the residential dwellings is energy consumption in the long-term use stage. However, the studies demonstrate further that this is a critical aspect regardless of the building type. Neither the different material structures, nor the manufacturing technologies, nor the energy standards of the four buildings affected significantly the qualitative patterns of results. All the more so as all the analyses were carried out simultaneously and by the same LCA team. The product systems were designed in the same way (system boundaries, allocation criteria), while the data were of comparable quality. However, perhaps the most important conclusion from the studies is that a key role is played not only by the quantity but also by a type of energy used. The analyses gave surprising results which showed that the passive buildings – whose overall energy demands were almost 3.6 times lower – gave worse results with regard to the use stage, which was due to the fact that 100% of the energy needs were covered by electricity. It is the high environmental burden of electricity production in Poland (90% of which is based on coal) that is a decisive factor that determines the final results of the environmental indicators for the passive houses. The above findings show that the results obtained in the studies should be interpreted only in the context of the assumptions and building projects, adopting particular (though not the only possible) materials and technological solutions. The scenario analyses show that making explicit judgments on the passive and conventional construction is risky, because it all depends on national, regional and local conditions. The same building used in different countries or even in different regions of the same country may have different environmental consequences, primarily due to a different structure of energy production, but also different technologies of final waste disposal. It can therefore be assumed that if the electric heating system was replaced with a gas heating system in the passive buildings, they would have significantly better cradle-to-grave results than their traditional counterparts. Against this background, the passive wooden house would be the preferred option as, in addition to lower energy demands, it has advantages also in the other life cycle stages, such as: lightweight building materials, the lowest waste generation in the life-cycle, the lowest impact of transport, the lowest water and energy consumption at the construction site.
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Contents lists available at ScienceDirect
Energy and Buildings journal homepage: www.elsevier.com/locate/enbuild
Comparative life cycle assessment of passive and traditional residential buildings’ use with a special focus on energy-related aspects Anna Lewandowska a,∗ , Andrzej Noskowiak b , Grzegorz Pajchrowski b a b
Faculty of Commodity Science, Poznan University of Economics, Al. Niepodleglosci 10, Poznan 61-875, Poland Wood Technology Institute, ul. Winiarska 1, Poznan 60-654, Poland
a r t i c l e
i n f o
Article history: Received 26 May 2013 Received in revised form 12 August 2013 Accepted 1 September 2013 Keywords: Energy consumption Environmental impact Buildings
a b s t r a c t This article presents the results of the research project financed by the Polish Ministry of Science and Higher Education (N N309 078138) and coordinated by the Wood Technology Institute in Poznan. A key point of this project was LCA study performed for four detached single-family dwellings with a particular emphasis on the use stage. The life-cycle assessment involved various types of activity made within a hundred years of use and related to: operation (energy and water consumption), replacements and repairs, renovations and maintenance, land occupation, waste transport and waste management. Two of the four analyzed buildings met passive house standards and their energy demands in the use stage were several times lower than those of their conventional counterparts. The aim of the studies was to demonstrate whether lower nominal energy consumption is sufficient to get the best results of the environmental impact of passive buildings, or whether a type of energy used to cover the demand also plays an important role. © 2013 Elsevier B.V. All rights reserved.
1. Introduction Sustainable construction is a response to the growing awareness of the negative impact of buildings on the environment as well as the health and lives of people [1]. In practice, different terms (ecological, green, energy-efficient) are used to describe the environmentally friendly construction. The sources of the concept can be found in a report of the World Commission on Environment and Development and the birth of the idea of sustainable development. According to it, sustainable construction is one that meets the needs of the present without compromising the ability of future generations to meet their own needs [2]. Sustainable construction has strong legislative justification that provides a backdrop to undertake such initiatives. Pursuant to the EU Directive 2002/91/EC, from January 2009, all real estate buildings newly put into use or marketed in Poland have to undergo Energy Performance Certification. In accordance with Directive 2010/31/EU, the EU Member States were obliged to change their national regulations on the energy performance of buildings by July 2012 to reduce energy consumption in the building sector by 20%. In addition, each constructed building will have to meet certain standards for minimum energy performance after July 2013 [1]. In the longer term, in accordance
∗ Corresponding author. Tel.: +48 618543121. E-mail address: [email protected] (A. Lewandowska). 0378-7788/$ – see front matter © 2013 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.enbuild.2013.09.002
with Directive 2010/31/EU, all new buildings will have to have a near-zero energy consumption after January 2021 (public buildings after 2018). The construction, as highly energy intensive sector, is strongly related to national energy system. In Poland the most strategic document in this area is Energy Policy of Poland until 2030 [3] and especially Appendix 2 [4]. The following targets for Polish energy system are assumed to achieve in coming fifteen years: an improvement of energetic effectiveness, an increase of security of fuel and energy supplies, a diversification of the structure of electrical energy production, including the introduction of nuclear energy, a development of use of renewable energy sources (including biofuels), a development of competitive markets of fuels and energy and a limitation of power energy effects upon the environment. A regulation of the Minister of Environment as of 20 December 2005 relating to emission standards for fuel combustion installations [5] and respective EU provisions [6–8] are also important documents from energy consuming long life buildings’ point of view. Due to the significant environmental impact of the construction sector, different measures are taken to make environmental assessment of construction activity. Due to the very long operation periods, versatility, high structural complexity and material comprehensiveness, buildings are a complex and unique objects of ecological studies. Life cycle assessment (LCA) [9,10] is one of the tools for the environmental assessment of solutions in the construction industry. LCA studies can be conducted for residential
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Fig. 1. LCA studies in the construction industry – objects and scopes. Source: [26].
or non-residential buildings [11–16] as well as civil and hydraulic engineering facilities, although these are less common [17–20]. As for the LCA scope, the literature [19,21–25] suggests analysing: Building Materials (BM), Component Combination (CC) and The Whole Process of the Construction (WPC). As a result, the LCA scope may be varied and refer to different buildings (Fig. 1). Full-scope LCA provides a full picture of environmental impacts and their sources, taking into account the whole life cycle of buildings. With this type of research, it is possible to define key issues such as: building materials and the related manufacturing technology, the use of a building, or perhaps issues related to waste management, transport or construction processes. Most studies have shown that the main environmental problem lies in the use stage energy consumption of buildings as energy-consuming facilities with a life cycle of at least decades. Thus, the tightening of legislation on building energy performance standards has profound environmental reasons. Sustainable construction is a response to changes taking place in legislation and awareness. A particular
example of sustainable building is passive construction, called super energy-saving because of the extremely low heat demand of the buildings (air heating in the ventilation system is often sufficient as the only heat source) [27]. The heat demand of passive buildings can be several times lower than that of their conventional counterparts. However, getting energy levels characteristic for passive buildings (annual heat demand of a building cannot exceed 15 kWh/m2 per year) is possible by increasing the consumption of building materials, especially insulation. Therefore, improvement is achieved in one life cycle stage, but at the cost of a deterioration in the others, because an increased use of building materials is not only related to a higher impact of their production, but also increased transport activity (both in the transport of new materials and waste) and the need for more waste management. LCAs of buildings can demonstrate whether such measures are environmentally “profitable” and whether the benefits of improved energy performance outweigh the negative impacts occurring in the other stages.
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This article presents the results of the LCA studies of four equivalent buildings, with a particular emphasis on the use stage. The environmental assessment involved different (energy and nonenergy-related) environmental interventions made during one hundred years of use of detached single-family dwellings. It was assumed that two of the four buildings met passive house standards and their energy demands were several times lower than those of their conventional counterparts. The aim of the studies was to demonstrate whether lower nominal energy consumption was sufficient to get the best results of the environmental impact of passive houses, or whether a type of energy used to cover that demand also played an important role. The studies assumed that the passive buildings, showing 3.6 times lower demand for heat, would be heated up with electric heaters, while the conventional buildings would be equipped with a gas heating system. In addition to the energy-related aspects, the analysis also involved other use-related issues: replacements and repairs, renovations and maintenance, land occupation, transport, water consumption, waste management and sewage treatment (generated throughout the entire use stage). The type and quantity of the materials used for replacement and repair depended on the structure of building materials and their manufacturing technologies. 2. A life cycle perspective The objects studied were four model one-family residential dwellings for a 4-person family with a usable area of 98.04 m2 . These buildings differed in material structure, manufacturing technology and energy performance standard. With regard to the first two criteria, the analyzed objects were two masonry and two wooden buildings. A wooden building should be understood as a material structure and manufacturing technology which maximizes the use of wood wherever it is technically and operationally justified. Therefore, it was assumed that wood and wood-based materials were used in the roofs of the wooden houses (rafter framing – coniferous timber, roofing material – wooden shingle), facade (board), floor (floor board), interior window sills and walls (OSB, MDF, HDF, cellulose). As for the masonry buildings, the use of wood was assumed only in rafter framing (coniferous timber). As for energy standards, two of the analyzed buildings met the requirements of passive houses, while the others were traditional buildings. Therefore, the studies involved: • • • •
Traditional masonry building (A1), Passive masonry building (A2), Traditional wooden building (B1), Passive wooden building (B2).
All of the buildings were single-storey houses with the following function program: entrance hall (lobby), toilet, living room with dining area, kitchen, double bedroom, two single rooms, bathroom and laundry room. An architectural firm prepared a separate architectural design for each of the buildings. The use of materials, performance parameters, equipment installation and energy consumption were calculated individually for each of the buildings, while for the options A2 and B2 it was done taking into account the requirements for passive buildings [27,28]. The buildings were located relative to the directions of the world in such a way as to maximize the effect of solar radiation (large windows in the south wall), which is particularly important for passive houses. The assumed location of the buildings is Poznan, placed in western Poland. The WPC studies involved the entire four buildings which were analyzed in the context of their full life cycle, including the following stages: production of building materials (stage 1), transport
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of building materials to the construction site (stage 2), construction (stage 3), use (stage 4), demolition (stage 5), demolition waste transport to the place of its final disposal (stage 6) and the final demolition waste disposal (stage 7). The buildings are multifunctional objects fit for fulfilling residential, protective, hygienic, aesthetic and construction functions, what can make an inclusion all of them to the functional unit problematic. The main functions taken into account in the studies were the residential and protective functions, based on which the functional unit of the studies was defined as: ensuring 98.04 m2 of habitable floor area for residential use within 100 years and protecting its users and objects against harmful effects of external factors during the period. Since the analyzed buildings have the same lifetime, the reference flow in each case is one building A1, A2, B1 or B2. Table 1 shows the general mass inputs and outputs and the final mass balance for the life cycles of the analyzed buildings. In order to make a balance, all inventory data, excluding electricity and heat, were converted to mass units. Natural gas consumption in the traditional buildings in the use stage was also excluded from the mass balance, because the inventory data related to gas combustion was taken from the ecoinvent database [29] where were expressed in energy units. If the input gas consumption had been expressed as mass, this would have required adding air to the inputs and emissions and waste to the outputs. As these data had already been included in the ecoinvent’s inventory table, it was assumed that the balance had been already made by the authors of the data and subject to verification in the ecoinvent validation process. The balance also excluded transport and demolition stages as they had no mass inventory data. The results in Table 1 show that the main mass flows in the life cycle of the analyzed buildings take place in the use stage, and cover over 98% of the total balance results. This applies to all the analyzed buildings, regardless of the manufacturing technology, material structure and energy performance. This is due to the fact that the balance for the use stage includes the mass flows of materials (inputs) and waste (outputs) generated over the 100-year time horizon, and arising out of repairs, replacements, renovations and maintenance, as well as water consumption and sewage production. 2.1. Stage 4 – use of the buildings – life cycle inventory In the present studies the building use stage was divided into seven areas: operation (energy and water consumption), replacements and repairs, renovations and maintenance, land occupation, waste transport and waste management. The scope of each area is characterized in Table 2. In addition, the following assumptions were made: • The time of use of a building is 100 years, • The amount of sewage is equal to water consumption, • Walls are painted with a frequency shown in Table 6, while the earlier layers of paint are not removed before the next painting. For this reason, the mass inputs of paint for renovations and maintenance in the use stage do not have their equivalents in the outputs, and appear only in the final demolition waste management (hence the difference in the mass inputs and outputs for stage 4 in the balance), • A similar assumption was applied to the painting of wooden doors and windows, with the difference that, in contrast to the walls, they are subject to replacements, whereas “accumulated” paint layers “leave” the use stage together with these elements. Those that relate to the last replacement before demolition appear in the outputs associated with the final demolition waste management, • In order to calculate the environmental impact of electricity consumption, inventory data representative for Poland are used as baseline scenario and taken from ecoinvent database v2.2.
13 254.37
Basic data and assumptions about the different areas of use are included in Tables 2–6. The water consumption was calculated using the guidelines included in the regulation of the Minister of Construction as of 14 January 2002 relating to determination of mean water consumption standards [30] and national statistics published by the Polish Central Statistical Office [31]. The energy consumption was calculated using the methodology of buildings energy certification and the technical data included in architectural projects. The calculations were carried out for assumed buildings’ location on the basis of meteorological data taken from the weather station in Poznan (52◦ 25 N, 16◦ 51 E). The annual values of heating degree day (HDD) and cooling degree day (CDD) specific for Poznan are: HDD = 3677 and CDD =120 (base temperature: 18 ◦ C) (). From life cycle inventory’s point of view, a short comment concerning data quality is needed. The uncertainty analyses showed that there was no significant difference in the quality of the data and the uncertainty of results between the buildings. Primary data were used for the same life cycle stages in all cases, and so were the secondary data (mainly from databases and literature): if used, they were consistent with similar areas in the life cycle of each building. 2.2. Stage 4 – use of the buildings – life cycle impact assessment
13 412.92 100.00 Total
13 385.41
13 385.41
100.00
13 412.92
100.00
100.00
13 310.17
100.00
13 310.17
100.00
100.00
13 254.37
100.00
According to this scenario the following shares of energy carries are assumed: hard coal 55.4%, brown coal 36.3%, natural gas 3.3%, crude oil products 1.6%, renewable energy 2.1%, pumped storage energy 1.1%, nuclear energy and waste energy 0.0%. In a case of gas consumption, ecoinvent data representative for Europe are used and a heat production based on natural gas, combusted at boiler modulating <100 kW assumed. This inventory module includes fuel input from low pressure (CH) network, infrastructure, emissions, and electricity needed for operation [29], • In the baseline scenario the above technological mix of production energy in Poland was assumed as static over the 100 years lifetime, but some additional scenarios are compared and presented in Section 3.
Source: [26].
0.00 1.41 13 160.18 92.77
Mg %
0.69 0.00 99.30 0.00 91.95 0.58 13 161.81 0.00
Mg %
0.00 0.01 98.85 1.14 0.00 1.40 13 156.83 151.95
Mg %
1.13 0.01 98.86 0.00 150.99 0.69 13 158.49 0.00
Mg %
0.00 0.04 98.15 1.81 0.00 5.25 13 164.25 243.42
Mg %
1.82 0.02 98.16 0.00 244.28 2.63 13 166.00 0.00
Mg %
0.00 0.03 98.33 1.64 0.00 3.84 13 162.48 219.08
Mg % Mg
1.63 0.02 98.35 0.00
Outputs Inputs Outputs Inputs Outputs Inputs
217.99 3.19 13 164.23 0.00 Stage 1 – production of building materials Stage 3 – building site (construction process) Stage 4 – use (100 years) Stage 7 – final disposal of demolition waste
Outputs Inputs
B2 – passive wooden building B1 – traditional wooden building A2 – passive, masonry building A1 – traditional, masonry building Life cycle stages
Table 1 Mass balance of the life cycles of the four buildings.
0.00 0.01 99.29 0.70
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%
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LCIA studies were conducted using SimaPro Analyst 7.3 and Impact 2002+ method, representing a combination of four LCIA methods: IMPACT 2002+ [32], Eco-indicator 99/E [33], CML [34] and the IPCC. At the most cumulative level, the environmental impact is an ecoindicator value expressed in points [Pt]. A cumulative ecoindicator result can be “broken down” into smaller components: weighted damage and impact category indicator results. Since Impact 2002+ is a combined method, the same damage and impact categories can be further analyzed at more desegregated levels: normalization and characterization (midpoint level). This article presents Eco-indicator results [Pt] and weighted impact category indicator results [Pt]. The higher the positive indicator, the greater the negative impact on the environment. A negative indicator is interpreted as an environmental benefit. Fig. 2 presents the environmental impacts of the life cycles of the analyzed buildings divided into different stages. As can be seen, the passive masonry building A2 has the highest impact (270.6 Pt), while the traditional wooden house B1 has the best result (230.7 Pt). The use stage had the greatest environmental impact for all the buildings, regardless of their material structures, manufacturing technologies and energy standards, but in the case of this stage the results had to be related to the energy performance of the buildings, since both traditional buildings showed lower environmental indicators than their passive counterparts. The environmental impact of the 100-year use of the house A1 was 229.5 Pt, A2 – 249.0 Pt, B1 – 223.2 Pt and B2 – 245.1 Pt. As for the masonry houses, stage 4 accounted for 92% of the cradle-to grave impact, and for the wooden houses, it was more than 95% (black in Fig. 2). This difference resulted from the material structure of the buildings and
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Table 2 Description of the areas included in Stage 4 – use of the buildings. Areas of use
Inventory data used in the study
Sources of assumptions and data
Operation
• Energy consumption for heating • Energy consumption for ventilation • Energy consumption in equipment • Energy consumption for cooling • Energy consumption for hot water preparation • Energy consumption for built-in lighting
• Data on heating, ventilation, cooling, hot water preparation and use based on architectural projects and energy certificates • Water and energy consumption for living purposes based on the Regulation of the Minister of Infrastructure of 14 January 2002 on the definition of the average water consumption standards and the Statistical Yearbook 2011
Replacements and repairs
• Consumption of building materials for replacement of selected components/building modules (Table 5) • Transport of building materials subject to replacements
• Replacement and repair frequency based on the literature and our own experience (as shown in Table 5)
Renovations and maintenance
• Consumption of building materials for renovation of selected elements/building modules (Table 6)
• Renovation frequency based on the literature and our own experience (as shown in Table 6)
Land occupation
• Land occupation
• Land occupation based on the building plot area and the time of use
Transport of building materials
• Transport of construction materials used for renovation and maintenance
• Cargo weight based on the use of construction materials in the individual components/modules of the house (without losses) • Distances calculated using vehicle route planning software • Information on the means of transport used to carry different types of building materials taken from the literature
Waste transport
• Transport of waste (after replacements and repairs, renovations and maintenance)
• Cargo weight based on the use of construction materials in the individual components/modules of a house (no losses) • Distances calculated using vehicle route planning software • Information on the means of transport used to carry different types of building materials taken from the literature
Waste management
• Sewage treatment and waste management (resulting from replacements and repairs, and renovations and maintenance)
• Type and amount of waste based on the use of building materials in the individual components/modules of a house subject to replacement • The amount of sewage generated based on water consumption
Source: [26].
lower environmental impact of stage 1 (production of construction materials) of the wooden houses B1 and B2 where a higher proportion of wood generated an environmental benefit in terms of climate change and Eco-indicator. The results obtained for the use of the buildings were divided into different areas in order to identify the source largely responsible for creating the negative impact. The data in Table 7 and Fig. 3 show that there is one major source of impact, i.e. operation which is responsible for creating 86–89% of impact throughout the use stage. Replacements and repairs take the second place (4–6%), and they are followed by land occupation (approximately 3%) and waste management (about 3%). The studies show that, in principle, there is one major source of the negative impact in the operation stage i.e. energy consumption. At the same time, the passive houses had worse results in this
regard (Table 8). The negative environmental impact generated by electricity consumption in the traditional houses was 66.4 Pt, and by heat energy consumption – 130 Pt. The former is nearly 30% of the total impact exerted in stage 4 and the latter – almost 60%. The situation is similar in the case of the passive houses, except that they use only electricity, the environmental impact of which is 215 Pt, which is in itself almost 90% of the indicator for the use stage. 3. Discussion and scenario analysis The total energy (gas and electricity) consumption (expressed in energy values, kWh) in the traditional buildings A1 and B1 is almost 3.6 times higher than the consumption in the passive buildings A2 and B2. However, the electrical energy consumption in the
Table 3 Annual consumption of utilities during the operation of the buildings. Operation A2 passive masonry building
B1 traditional wooden building
B2 passive wooden building
Unit
Inventory element
A1 traditional masonry building Consumption
Electricity – rtv and household equipment Electricity – lighting Electricity – heating Electricity – hot tap water Electricity – ventilation Heat (natural gas) – heating Heat (natural gas) – hot tap water Electricity (ancillary) Hot water (55 ◦ C) Cold water Sewage
1 600.0 350.0 – – – 15 637.7 6 584.5 130.8 45 990.0 85 410.0 131 400.0
1 600.0 350.0 1 429.5 3 010.9 343.5 – – – 45 990.0 85 410.0 131 400.0
1 600.0 350.0 – – – 15 484.7 6 584.5 130.8 45 990.0 85 410.0 131 400.0
1 600.0 350.0 1 470.4 3 010.9 343.5 – – – 45 990.0 85 410.0 131 400.0
kWh/year kWh/year kWh/year kWh/year kWh/year kWh/year kWh/year kWh/year L/year L/year L/year
Building
Source: [26,30,31].
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Table 4 Energy consumption in the buildings A1, A2, B1 and B2 during the 100 years of use. Inventory element
A1 traditional masonry building
B1 traditional wooden building
Unit
Comment
Electricity Electricity Natural gas Natural gas Electricity
160,000 35,000 1,563,769 658,446 13,076
160,000 35,000 1,548,468 658,446 13,076
kWh kWh kWh kWh kWh
Rtv and household equipment Lighting Heating Hot water (55 ◦ C) Electricity (ancillary)
Total As electricity Electricity
2,430,291 8.6 160,000
2,414,990 8.6 160,000
kWh % kWh
Inventory element
A2 passive masonry building
B2 passive wooden building
Unit
Comment
Electricity Electricity Electricity Electricity Electricity
160,000 35,000 142,950 301,091 34,353
160,000 35,000 147,037 301,091 34,353
kWh kWh kWh kWh kWh
Rtv and household equipment Lighting Heating Hot water (55 ◦ C) Ventilation
Total As electricity As natural gas
673,394 100.00 00.00
677,481 100.00 00.00
kWh % %
Source: [26,30,31].
Table 5 Durability of components subject to replacements and repairs for the four technological variants of the analyzed buildings. Replacements and repairs B1 traditional wooden building
Building
A1 traditional masonry building
A2 passive masonry building
Inventory element
Durability [years]
Number of replacements [times]
Durability [years]
Number of replacements [times]
Durability [years]
Number of replacements [times]
Durability [years]
Number of replacements [times]
Constructional elements Windows Internal doors External doors Wood flooring Gas heating system (without boiler) Gas boiler Ceramic tiles (floor and walls) Power supply system Water supply system Sewage system Ventilation system Roof gutter system Roof covering Rafter framing (selected elements) Roof insulation Ceiling insulation External wall insulation Internal walls insulation Fac¸ade
100 25 30 30 – 50 20 20 50 50 50 – 50 50 50 50 50 – – –
0 3 3 3 – 1 4 4 1 1 1 – 1 1 1 1 1 – – –
100 25 30 30 – – – 20 50 50 50 50 50 50 50 50 50 50 – –
0 3 3 3 – – – 4 1 1 1 1 1 1 1 1 1 1 – –
100 25 30 30 50 50 20 20 50 50 50 – 50 50 50 50 50 50 50 50
0 3 3 3 1 1 4 4 1 1 1 – 1 1 1 1 1 1 1 1
100 25 30 30 50 – – 20 50 50 50 50 50 50 50 50 50 50 50 50
0 3 3 3 1 – – 4 1 1 1 1 1 1 1 1 1 1 1 1
B2 passive wooden building
Source: [26]. Source: [26]
Table 6 Durability of components subject to renovations and maintenance for the four technological variants of the analyzed building. Renovations and maintenance Building
A1 traditional masonry building
A2 passive masonry building
Inventory element
Durability [years]
Number of replacements [times]
Durability [years]
Number of replacements [times]
Durability [years]
Number of replacements [times]
Durability [years]
Number of replacements [times]
Internal wall painting External wall (fac¸ade) painting External door painting Internal door painting Wood window painting Wood floor varnishing
5 25 10 15 -
19 3 6 3 -
5 25 10 15 -
19 3 6 3 -
5 25 10 15 5 25
19 2 6 3 19 2
5 25 10 15 5 25
19 2 6 3 19 2
Source: [26].
B1 traditional wooden building
B2 passive wooden building
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B2 - PASSIVE, WOODEN BUILDING
B1 - TRADITIONAL, WOODEN BUILDING
A2 - PASSIVE, MASONRY BUIDLING
A1 TRADITIONAL, MASONRY BUIDLING
-50
0
50
100
150
200
250
300
Environmental impact [Pt] STAGE 1 - PRODUCTION OF BUIDLING MATERIALS
STAGE 2 - TRANSPORT OF BUILDING MATERIALS
STAGE 3 - BUIDLDING SITE (CONSTRUCTION PROCESS)
STAGE 4 - USE (100 YEARS)
ETAP 5 - DEMOLITION
ETAP 6 - TRANSPORT OF WASTE AFTER DEMOLITION
STAGE 7 - FINAL DISPOSAL OF WASTE AFTER DEMOLITION
Fig. 2. Eco-indicator results for particular life cycle stages of the analyzed buildings (baseline scenario) [Pt]. Source: [26].
Table 7 Contribution of different areas of use to the negative environmental impact. Areas of use
A1 traditional, masonry building
A2 passive, masonry building
B1 traditional wooden building
B2 passive wooden building
[Pt]
[Pt]
[Pt]
Environmental impact [Pt] Land occupation Operation Replacements and repairs Renovations and maintenance Transport of building materials Transport of waste Final disposal of waste
7.0 198.5 13.5 1.7 1.8 0.02 7.0
Total
229.5
[%] 3.0 86.5 5.9 0.7 0.8 0.009 3.0 100.0
7.0 217.0 15.7 1.7 1.7 0.02 5.2 249.0
[%] 2.8 87.1 6.3 0.7 0.7 0.008 2.1 100.0
[%]
7.0 198.0 15.8 1.7 0.8 0.03 6.1
3.1 86.3 6.9 0.7 0.3 0.01 2.7
223.2
100.0
[%]
7.0 218.0 9.8 1.7 0.8 0.03 7.2
2.9 89.1 4.0 0.7 0.3 0.0 2.9
245.1
100.0
Source: [26].
Environmental impact [Pt]
traditional buildings accounts for only about 31% of energy consumption in the passive buildings. The reasons for the differences in the results of environmental indicators should be sought in different environmental burden of electricity and heat production from natural gas. According to the technological scenario for Poland the production of 1 kWh of electricity has an environmental impact of 0.000321 Pt, and the acquisition of 1 kWh of heat energy from natural gas has an environmental impact of 0.0000603 Pt. Thus, 1 kWh of electricity is 5.3 times worse environmentally than the equivalent amount of energy acquired directly from natural gas combustion. In both cases, the impact categories largely affected by
the negative effects are: respiratory disorders/inorganic compounds, global warming and non-renewable energy, which is a typical picture of the environmental impact of combustion processes based on non-renewable energy sources (Table 9). From the perspective of the environmental impact, the use of the analyzed buildings is dominated by energy issues, so the structure of the environmental impact of this stage (but also the whole life cycle) corresponds to the image of the typical effect of energy production (Fig. 4). It is dominated by three impact categories. Two output related categories: respiratory disorders resulting from emissions of inorganic compounds (mainly carbon dioxide,
250 225 200 175 150 125 100 75 50 25 0
A1
Land occupation Renov ations and maintenance Renovations conservations Final disposal of waste
A2
B1
Operation Transport of building materials
B2
Replacements and repairs Transport of waste
Fig. 3. Eco-indicator results for particular areas of stage 4–100 years of buildings’ use (baseline scenario) [Pt]. Source: [26].
231.8
94.6
0.2 0.5 0.3
94.8
0.6
211.7
0.5 1.1 0.7
94.4
1.7
235.1
Steel radiators
0.6 1.3 1.4 3.5
Windows
• Scenario DK – energy demand in the use stage of all the four buildings is covered by electricity produced in accordance with the current mix of energy production in Denmark [29], • Scenario DE – energy demand in the use stage of all the four buildings is covered by electricity produced in accordance with the current mix of energy production in Germany [29], • Scenario PL – energy demand in the use stage of all the four buildings is covered by electricity produced in accordance with the structure of energy production assumed for Poland in the following years: - Scenario PL 2020 – the energy mix for 2020 year assumed according to Energy Policy of Poland until 2030 [3,4] where the increase in share of renewable energy (19.3%) and the initiation of nuclear energy production (6.7%) are the most significant changes in comparison to baseline scenario, - Scenario PL 2025 – the energy mix for 2025 year assumed according to Energy Policy of Poland until 2030 [3,4] where increased share of nuclear energy (11.7%) and decreased consumption of coal are the most significant changes in comparison to previous scenarios, - Scenario PL 2030 – the energy mix for 2030 year assumed according to Energy Policy of Poland until 2030 [3,4] where increased share of nuclear energy up to 15.7% is the most important change in comparison to previous scenarios, - Scenario PL 2050 – the energy mix for 2050 year assumed according to Energy mix for Poland – scenarios 2050 [35] where really high share of nuclear energy (23%) and very low contribution of coal (13.2% hard coal and 7.8% brown coal) are the most important modifications in comparison to previous scenarios. The electricity production mix 2050 prepared by Institute for Structural Research (IBS) was selected for calculations (Table 10).
0.6
94.2
1.3
216.3 Source: [26].
Fig. 5 and Table 11 presented below show the results of the cumulative eco-indicator for the adopted scenarios in comparison to baseline scenario. As can be seen, the indicators for the passive houses clearly decrease and the ranking of the buildings varies substantially. The following observations can be made:
Total
Replacements and repairs
1.5 3.5
Ceramic tiles/bathroom Electric cables Replacements and repairs
Replacements and repairs
1.0 2.3 Windows
Ceramic tiles/bathroom Electric cables
1.0 2.5 1.4 3.1 Ceramic tiles/floor Replacements and repairs
nitrogen oxides, sulfur oxides and particulate matter) to atmosphere and climate change (mainly due to emissions of carbon dioxide, and methane to a much lesser extent). The third inputrelated impact category is the depletion of non-renewable energy resources. As shown hereinabove, the use stage, and in principle, energy consumption in this stage, turned out to be the main source of the negative environmental impact during the life cycle of all the analyzed buildings. The main issue in the case of the passive houses was the fact that their energy demands were fully satisfied with electricity generated in accordance with the structure of energy production typical of Poland. And even the fact that the overall energy demands of these buildings were several times lower compared to those of the conventional buildings did not wipe out this difference. It can therefore be concluded that not only the quantity but also a type of energy used plays a critical role. It was therefore decided to make a scenario analysis and conduct analogous LCIA studies for the buildings, but under slightly modified assumptions. Due to the fact that the passive construction is especially popular in Germany and Scandinavia, the following three scenarios were adopted (for all three scenarios the same energy consumption values during 100 years are assumed as in the baseline scenario presented in chapter 2):
Cellulose
0.6 1.5
1.6 3.5
3.7 1.2 9.6 3.1 28.9 4.1 Operation Operation
66.6 9.6
Windows
86.3 56.8 130.4
Sewage treatment Ceramic tiles/floor
%
215.0
% Pt
Operation
Heat energy from natural gas Electricity Sewage treatment
Electricity
Pt
Ceramic tiles/bathroom Electric cables
29.7 4.2 66.4 9.6
Windows
0.7 1.7
3.9 1.4 9.6 3.5
58.0
Sewage treatment Ceramic tiles/bathroom Electric cables
%
87.7 215.0
Pt %
129.5
Heat energy from natural gas Electricity Sewage treatment
Pt
Electricity
Inventory point Eco-indicator result
B1 traditional wooden building
Inventory point Eco-indicator result
A2 passive masonry building
Inventory point Eco-indicator result
A1 traditional, masonry building
Inventory point
Areas of use
Table 8 Inventory data for Stage 4 (use) primarily responsible for creating the negative environmental impact.
Eco-indicator result
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B2 passive wooden building
642
• All the additional scenarios give lower environmental impact than baseline scenario, regardless of the type of the building. The passive houses have the best results in the scenarios where electricity demand is covered in accordance with the German
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Table 9 Environmental impact of 1 kWh of electricity and heat from natural gas for the three selected impact categories. Impact category
Weighted impact category indicator result
Electricity (energy mix in poland) Respiratory inorganics
Characterized impact category result
0.0000925
Pt
Global warming Non renewable energy
0.000115 0.0000906
Pt Pt
Heat energy from natural gas Respiratory inorganics
0.00000331
Pt
0.0000335
kg PM 2.5 equiv.
Global warming
0.0000246
Pt
0.243
kg CO2 equiv.
Non renewable energy
0.0000308
Pt
4.68
MJ primary
0.000938
1.14 13.8
Environmental intervention
kg PM 2.5 equiv.
NOx – 26% (1.92 g) PM 2.5 – 31.7% (297 mg) SOx – 42.2% (5.07 g) CO2 – 97.8% (1 119.78 g) Brown coal – 35.1% (488 g) Hard coal – 55.8% (402 g) Natural gas – 3.65% (12.49 dm3 )
kg CO2 equiv. MJ primary
NOx – 57.7% (152 mg) PM 2.5–13.5% (4.52 mg) SOx – 28.7% (123 mg) CO2 – 96.6% (235 g) Methane – 3.13% (1.09 g) Natural gas – 96.8% (112 dm3 )
Source: [26].
Fig. 4. The weighted impact category indicator results for stage 4–100 years of buildings’ use (baseline scenario) [Pt]. Source: [26].
Table 10 Technological mix of electricity production in Poland in baseline scenario and selected years (2020, 2025, 2030 and 2050) [%]. Energy carriers Hard coal Brown coal Natural gas Crude oil products Nuclear energy Renewable energy Including: water energy Including: wind energy Including: biomass Including: biogas Including: solar energy Including: geothermal energy Pumped-storage energy Waste In total Source: [3,4,26,29,35]. a Not included in the scenario.
Baseline scenario (%)
Scenario PL 2020 (%)
Scenario PL 2025 (%)
Scenario PL 2030 (%)
55.4 36.3 3.3 1.6 0.0 2.2 1.5 0.1 0.5 0.1 0.0 0.0 1.1 0.0
40.2 25.6 5.4 1.8 6.7 19.3 1.0 4.4 10.1 3.7 0.0 0.0 0.6 0.4
32.4 26.8 6.3 1.6 11.7 20.2 0.9 5.0 9.3 5.1 0.0 0.0 0.6 0.4
35.6 21.0 6.6 1.5 15.7 18.8 0.8 4.6 8.5 4.9 0.0 0.0 0.5 0.3
100.0
100.0
100.0
100.0
Scenario PL 2050 (%) 13.2 7.8 6.0 0.0a 23.0 50.0 4.0 30.0 8.0 0.0 6.0 2.0 0.0a 0.0a 100.0
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Environmental impact [Pt]
300 250 200 150 100 50 0 Baseline scenario
Scenario DE
Scenario DK
A1
Scenario PL 2020
A2
B1
Scenario PL 2025
Scenario PL 2030
Scenario PL 2050
B2
Fig. 5. Environmental impact the whole life cycle of the buildings A1, A2, B1, B2 – electricity in accordance with different technological mix scenarios [Pt].
(Scenario GE) and Danish (Scenario DK) systems and with Polish situation in 2050 year (Scenario PL 2050). The ecoindicator values for these three scenarios decreased from 34.7% (A2, scenario DE) to even 49.8% (B2, scenario PL 2050), in comparison to baseline scenario. The relationships between LCIA results for all analyzed buildings are similar in these three scenarios what resulted from the fact that in 2050 year the Polish energy mix is assumed to reach the structure corresponding to Western countries’ electricity production, • According to Polish scenario in 2020 year the conventional houses are still better, but the superiority is minimal. While the difference between ecoindicator results was 21.5 Pt (A2–A1) and 26.2 Pt (B2–B1) in the baseline scenario, in 2020 year it reduced to 0.3 Pt and 5.0 Pt, respectively. It can be stated than in 2020 year
is that time where the environmental impact of buildings A1 and A2 is equalized. The year for equalizing the results of B1 and B2 is about 2023, since in 2025 the environmental impact of passive house B2 is lower (B1 = 218.3 Pt, B2 = 215.6 Pt), • The lowest indicator result was recorded for the wooden passive house B2. In this case, the reduction in the energy-related environmental burden is enhanced by the positive image of impacts of wood and wood-based building materials. Declines in the indicators can be explained by differences in the environmental burden of energy production in the analyzed countries. According to baseline scenario the production of 1 kWh of electricity in Poland has an environmental impact of 0.00032 Pt, while in Germany – 0.00018 Pt, and in Denmark – 0.00016 Pt.
Table 11 Environmental impact the whole life cycle of the buildings under the assumption that electricity consumed in the use stage is produced according to different electricity mix scenarios. A1 traditional masonry building
A2 passive masonry building
B1 traditional wooden building
B2 passive wooden building
Electricity production according to the current polish energy system (baseline scenario) 249.1 270.6 Eco-indicator result [Pt]
230.9
257.1
Electricity production according to the danish energy system (scenario DK) 215.8 Eco-indicator result [Pt] ↓ 33.3 Change [Pt] (in relation to baseline scenario) ↓ 13.4 Change [%] (in relation to baseline scenario)
162.7 ↓ 107.9 ↓ 39.9
197.5 ↓ 33.4 ↓ 14.4
148.5 ↓ 108.6 ↓ 42.2
176.7 ↓ 93.9 ↓ 34.7
201.8 ↓ 29.1 ↓ 12.6
162.6 ↓ 94.5 ↓ 36.8
Electricity production according to the polish energy system in 2020 year (scenario PL 2020) Eco-indicator result [Pt] 239.7 240.0 Change [Pt] (in relation to baseline scenario) ↓ 9.4 ↓ 30.6 ↓ 3.8 ↓ 12.3 Change [%] (in relation to baseline scenario)
221.3 ↓ 9.6 ↓ 3.9
226.2 ↓ 30.9 ↓ 12.4
Electricity production according to the polish energy system in 2025 year (scenario PL 2025) Eco-indicator result [Pt] 236.4 229.4 ↓ 12.7 ↓ 41.2 Change [Pt] (in relation to baseline scenario) ↓ 5.1 ↓ 16.5 Change [%] (in relation to baseline scenario)
218.0 ↓ 12.9 ↓ 5.2
215.6 ↓ 41.5 ↓ 16.6
Electricity production according to the polish energy system in 2030 year (scenario PL 2030) 235.3 226.0 Eco-indicator result [Pt] ↓ 13.8 ↓ 44.6 Change [Pt] (in relation to baseline scenario) ↓ 17.9 ↓ 5.5 Change [%] (in relation to baseline scenario)
216.9 ↓ 14.0 ↓ 5.6
212.2 ↓ 44.9 ↓ 18.0
Electricity production according to the polish energy system in 2050 year (scenario PL 2050) 211.0 147.3 Eco-indicator result [Pt] ↓ 38.1 ↓ 123.3 Change [Pt] (in relation to baseline scenario) ↓ 15.3 ↓ 49.5 Change [%] (in relation to baseline scenario)
192.6 ↓ 38.3 ↓ 15.4
133.0 ↓ 124.1 ↓ 49.8
Electricity production according to the german energy system (scenario DE) Eco-indicator result [Pt] 220.1 ↓ 29.0 Change [Pt] (in relation to baseline scenario) ↓ 11.7 Change [%] (in relation to baseline scenario)
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Therefore, only half of the impact can be explained by a smaller share of coal (47.6% in Germany, 47.9% in Denmark, while 91.7% in Poland), a higher share of gas (11.4% in Germany, 23.5% in Denmark and 3.3% in Poland) and above all a higher share of RES (10.5% in Germany, 14.1% in Denmark and 3.2% in Poland) in the energy systems of Germany and Denmark, compared to baseline Polish scenario. The contribution of nuclear energy is next strongly important element. The lower environmental impact of all additional scenarios directly resulted from the fact that part of electricity was assumed to be produced in nuclear power plants. In baseline scenario (corresponding to current situation in Poland) the share of nuclear energy is assumed as zero. According to scenario PL 2050 all energy from coal and natural gas should be produced using Carbon Capture and Storage (CCS) technology. Because of lack of appropriate inventory data, the fact of CCS technology use was not included in the calculations. It is highly probable that this kind of inclusion would give even more reduction of ecoindicator results for the passive houses, especially in relation to clime change impact category.
4. Conclusions The studies show that the main source of the negative environmental impact in the life cycles of the residential dwellings is energy consumption in the long-term use stage. However, the studies demonstrate further that this is a critical aspect regardless of the building type. Neither the different material structures, nor the manufacturing technologies, nor the energy standards of the four buildings affected significantly the qualitative patterns of results. All the more so as all the analyses were carried out simultaneously and by the same LCA team. The product systems were designed in the same way (system boundaries, allocation criteria), while the data were of comparable quality. However, perhaps the most important conclusion from the studies is that a key role is played not only by the quantity but also by a type of energy used. The analyses gave surprising results which showed that the passive buildings – whose overall energy demands were almost 3.6 times lower – gave worse results with regard to the use stage, which was due to the fact that 100% of the energy needs were covered by electricity. It is the high environmental burden of electricity production in Poland (90% of which is based on coal) that is a decisive factor that determines the final results of the environmental indicators for the passive houses. The above findings show that the results obtained in the studies should be interpreted only in the context of the assumptions and building projects, adopting particular (though not the only possible) materials and technological solutions. The scenario analyses show that making explicit judgments on the passive and conventional construction is risky, because it all depends on national, regional and local conditions. The same building used in different countries or even in different regions of the same country may have different environmental consequences, primarily due to a different structure of energy production, but also different technologies of final waste disposal. It can therefore be assumed that if the electric heating system was replaced with a gas heating system in the passive buildings, they would have significantly better cradle-to-grave results than their traditional counterparts. Against this background, the passive wooden house would be the preferred option as, in addition to lower energy demands, it has advantages also in the other life cycle stages, such as: lightweight building materials, the lowest waste generation in the life-cycle, the lowest impact of transport, the lowest water and energy consumption at the construction site.
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