Retrofitting with different building materials: Life-cycle primary energy implications

Journal Pre-proof Retrofitting with different building materials: life-cycle primary energy implications

C. Piccardo, A. Dodoo, L. Gustavsson, U.Y.A. Tettey PII:

S0360-5442(19)32343-6

DOI:

https://doi.org/10.1016/j.energy.2019.116648

Reference:

EGY 116648

To appear in:

Energy

Received Date:

08 May 2019

Accepted Date:

27 November 2019

Please cite this article as: C. Piccardo, A. Dodoo, L. Gustavsson, U.Y.A. Tettey, Retrofitting with different building materials: life-cycle primary energy implications, Energy (2019), https://doi.org/10. 1016/j.energy.2019.116648

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Journal Pre-proof Retrofitting with different building materials: life-cycle primary energy implications C. Piccardoa,*, A. Dodoob, L. Gustavssonb, U. Y. A. Tetteyb a Department of Architecture and Design, University of Genoa, Stradone S. Agostino 37, 16123 Genoa, Italy b Sustainable Built Environment Research Group, Department of Built Environment and Energy Technology, Linnaeus University, Växjö, SE-35195, Sweden

Abstract The energy retrofitting of existing buildings reduces the energy use in the operation phase but the use of additional materials, influence the energy use in other life cycle phases of retrofitted buildings. In this study, we analyse the life cycle primary energy implications of different material alternatives when retrofitting an existing building to meet high energy performance levels. We design retrofitting options assuming the highest and lowest value of final energy use, respectively, for passive house standards applicable in Sweden. The retrofitting options include the thermal improvement of the building envelope. We calculate the primary energy use in the operation phase (operation primary energy), as well as in production, maintenance and end-of-life phases (non-operation primary energy). Our results show that the non-operation primary energy use can vary significantly depending on the choice of materials for thermal insulation, cladding systems and windows. Although the operation energy use decreases by 50-62%, we find that the non-operation energy for building retrofitting accounts for up to 21% of the operation energy saving, depending on the passive house performance level and the material alternative. A careful selection of building materials can reduce the non-operation primary energy by up to 40%, especially when using wood materials.

Keywords Building retrofit; Passive house; Life cycle; Primary energy use; Building materials.

Declarations of interest: none

*

Corresponding author.

E-mail address: [email protected] (C. Piccardo).

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Journal Pre-proof 1. Introduction The building sector, accounting for 40% of the European Union’s (EU’s) final energy use [1], plays an important role in the transition to a sustainable energy system [2]. The EU Directive 2018/844 requires minimum energy performance not only for new buildings, but also for existing buildings liable to significant renovation, and encourages Member States to increase the number of high energy performance buildings [3]. The definition of high energy performance building vary widely among European countries [4], but the energy efficiency measures usually focus on the energy use for water and space heating, and next on the use of renewable energy sources and the energy use for cooling [5]. The passive house concept is a model for high performance buildings with improved insulation and airtightness, energy-efficient windows and heat recovery from exhaust ventilation air [6]. Energy retrofit of existing buildings is important for a transition to low energy built environment in the EU, as the existing building stock is estimated to be about 70% of the 2050 building stock [7]. Furthermore, about 50% of the existing residential buildings were built before energy efficiency standards were introduced in building codes in most EU countries, in the 1970s [8]. In Sweden, 30% of the current building stock was built between 1961 and 1975 [9] and these are expected to require major renovations in the coming years [10]. The operation energy use of new and retrofitted buildings is expected to decrease, due to implementation of energy efficiency measures. However, this may influence the non-operation primary energy use in the other life cycle phases of buildings. Sartori and Hestnes [11] reviewed life cycle studies, finding that the production energy is usually higher in high energy performance buildings than in conventional ones. Cellura et al. [12] discussed the production energy use in different climate zones. Chastas et al. [13] showed that non-operation energy in passive house buildings ranges between 11 and 57% of the life cycle primary energy. This is consistent with an average value of 25% found by Karimpour et al. [14]. Retrofitting measures typically used to meet high energy performance levels usually result in increased building production energy, but contribute to save between 30 and 80% of operation energy in the remaining life of retrofitted buildings [15]. The relevance of the non-operation energy when retrofitting an existing building depends on the adopted retrofitting measures. A Swedish study [16] found that the production primary energy of a building retrofitted to meet the passive house standard ranges between 1 and 13% of the operation primary energy saving, depending on the efficiency of the heating and energy supply systems. Similarly,

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Journal Pre-proof Asdrubali et al. [17] estimated that the non-operation primary energy use, including production, maintenance and end-of-life phases, of high energy performance retrofitted buildings ranges between 6 and 13% of the operation primary energy saving, depending on the efficiency of building systems, as well as the amount of insulation material needed. Beccali et al. [18] found that the non-operation energy use in high energy performance retrofitted buildings accounts for over 20% of the operation energy saving. Furthermore, the thermal improvement of the building envelope is the most relevant retrofitting measure in terms of nonoperation primary energy use. An Italian extensive study [19] on the effectiveness of energy efficiency policies showed that the installation of new windows results in lower net primary energy saving compared to the extra insulation of external walls due to the higher non-operation primary energy. Studies [20,21] also point out efficient post-use management of building materials to reduce the total primary energy use of retrofitting buildings. The selection of materials in retrofitted buildings might affect the net primary energy saving significantly.However, studies of non-operation energy when using different material to retrofit existing buildings are mostly lacking. The aim of this study is to analyse the implications of using different building materials for retrofitting existing buildings to passive house standard. The complete life cycle in retrofitting a building is considered including production, operation, maintenance and end-of-life, when comparing different insulation materials, façade systems and glazing components. The final and primary energy use, as well as the net primary energy benefits, are calculated for each retrofitting option.

2. Study descriptions and assumptions 2.1 Analysed building The analysis is based on a typical 3-storey multi-family building from the Swedish million homes programme [22], located in Ronneby municipality in southern Sweden. It was built in 1972, before energy efficiency was emphasised in the Swedish building code in 1977. The heated living area of the building is 2000 m2, divided into 27 apartments, and a basement of 600 m2 below the ground level. The load bearing structure consists of in-situ concrete frame. The façades are insulated with 95-120 mm of mineral wool and/or polystyrene while the basement walls are not insulated. The attic is insulated with 120 mm mineral wool panels and can still contain further insulation. The façades are mainly covered with bricks

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Journal Pre-proof but also with wood panels (East- and West-facing walls). The building has mechanical exhaust ventilation system and is connected to the local district heating system (DHS) providing tap water and space heating.

2.2 Passive house standard Different passive house criteria are recommended for improved building energy efficiency [23]. In Sweden, three different passive house standards can be applied on a voluntary basis: FEBY12 [24]; Wahlström et al. [25]; and Passive House Institute (PHI) [26] (Table 1). The highest and lowest final energy use for space and tap water heating is 50 kWh/m2 and 30 kWh/m2, respectively, in these standards. The highest value is achievable with cost-effective retrofitting measures [27] while the lowest value requires further improvements in the building envelope. We retrofit the building to 50 kWh/m2 (PH50) or 30 kWh/m2 (PH30) final energy use for heating. The retrofitting measures are divided in two categories: upgrade of technical devices for space and tap water heating; thermal improvement of the building envelope. The initial mechanical exhaust ventilation system is changed to a ventilation system with heat recovery units, with energy efficiency of fans and ventilation heat recovery (VHR) unit of 50% and 85%, respectively, in both passive house levels. The final energy use for tap water heating is reduced by 40% through resource-efficient taps [27], for both passive house levels. Electrical appliances are assumed to be unchanged. Next, we apply extra insulation to the initial building to achieve the PH50 and PH30 final energy use, respectively, using the most common cost-efficient practice and starting from the basement and attic areas [28, 29]. The calculated insulation thickness varies depending on the passive house level and insulation material (Table 2). The initial air leakage rate of 0.8 l/s m2 at 50 Pa pressure [27] is improved to 0.3 l/s m2. The initial windows U-value of existing of 2.9 kWh/m2 is lowered for new widows to 0.8 and 0.6 kWh/m2 in the PH50 and PH30 buildings, respectively.

2.3 Material alternatives We select different materials for the thermal insulation, external building cladding, and windows. Next, we combined different materials together to compare the maximum number of retrofitting options. The selected materials are described below.

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Journal Pre-proof 2.3.1 Thermal insulation Improved thermal insulation is an efficient strategy to meet high energy-efficiency standards [30, 31], also emphasized by the EU Directive 2018/844 and national building codes [4]. This can significantly decrease the final energy use for space heating in retrofitted buildings, as shown in [32, 33]. Nevertheless, the use of different insulation materials affects the production primary energy use of retrofitted buildings [34, 35]. Here, we select glass wool, rock wool and wood fibre, as common insulation materials [29, 33]. Extruded polystyrene (XPS) is selected for the basement insulation because of its moisture resistance.

2.3.2 Building claddings Improving thermal insulation of external walls usually entails new building claddings. The choice of cladding materials depends on several factors, including architectural issues, technical requirements, budget and users’ perception. Only a few life cycle analysis of buildings [20, 36, 37] report the primary energy use of cladding materials, which varies depending on the material. Other studies highlight that the production phase mainly contributes to the energy use of cladding materials [38, 39, 40]. We select wood and bricks, as common cladding materials used in retrofitting works in Sweden [41], and aluminium, as an energy intensive material.

2.3.3 Energy-efficient windows A maximum U-value of 0.8 W/m2K is recommended for windows in passive houses [24, 42]. The overall Uvalue of windows depends on the glazing unit and window frame. The U-value of glazing units can be improved by extra glazed panes, low-emittance coating and high-density gas fill. Some studies [43, 44] report that triple-glazed windows have suitable U-values for passive houses. Low emittance coatings can reduce the U-value and emittance of the glazing unit by approximately 0.1 W/m2K and 3%, respectively [45]. Argon and krypton fillings are used in energy efficient windows [46, 47]. The U-value of window frames can be about 0.6-0.8 W/m2K [46, 47] by using spacers with improved thermal insulation, thermal breaks and extended glazing gaskets [48]. Gustavsen et al. [49] show that equal thermal performance is achievable with different frame materials. In Sweden, windows with U-values of 0.7–0.6 W/m2K are available on the market [50], but commercially best available technologies can improve the U-value of windows to 0.4 W/m2K [43]. We assume U-values of windows of 0.8 and 0.6 W/m2K for the PH50 and PH30 buildings, respectively. The U-values of

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Journal Pre-proof the PH50 and PH30 windows are achievable with triple-glazed single low-e coated and argon-filled windows and with triple-glazed double low-e coated and krypton-filled windows, respectively. We select wood and aluminium for window frames.

3. Method 3.1 General approach The study integrates dynamic energy modelling and bottom-up life cycle analysis to explore the energy implications of the different material alternatives for building retrofitting. The dynamic energy modelling allows design of thermally-equivalent retrofitting options for each passive house standard. Then, we use a bottom-up approach to analyse the life cycle primary energy use of the retrofitted building elements, as well as the net primary energy benefit from material recovery. The life cycle analysis is developed according to ISO 14040 [51] and EN 15978 [52]. We assume that each retrofitted building element is assembled at the current time and disassembled after 50 years.

3.2 Energy scenarios We consider the effects from expected changes in production, use and disposal of building materials within the life cycle of the building being retrofitted. Therefore, we consider marginal changes, for example, for the marginal electricity, we assume the most likely marginal energy source of the electricity supply system instead of its historical average energy mix. Marginal electricity in the Nordic region is often produced by coal-based power plant [53, 54], but it is expected to be produced by fossil gas-based plants in future [54]. Several studies assume coal as marginal source for electricity production [33, 37, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64]. We consider electricity produced in fossil coal-based stand-alone plants. In a sensitivity analysis we show the impact of variation of marginal source for electricity production, assuming fossil gas-based plants.

3.3 Dynamic energy modelling We perform dynamic hourly energy balance calculations of the initial and retrofitted buildings using the VIPEnergy simulation software [65], which is validated by the International Energy Agency Building Energy

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Journal Pre-proof Simulation Test and diagnostic method (IEA BESTEST). The final energy use includes space and tap water heating, as well as electricity for ventilation. Energy for domestic purposes is not included. The following input data are used in the energy modelling: hourly weather data for Ronneby in 2013 [66]; indoor air temperatures of 22°C and 18° C for the living and common areas, respectively; internal heat gains from building occupants and electrical appliances of 2.16 and 3 W/m2, respectively, with a constant profile over the year; tap water heat consumption (kWh) based on standard equation from Boverket [67], calculated to be equal to 1800 × number of apartments + 18 × heated area [m2]. More details are given by Dodoo et al. [68], who analyse appropriate parameter values and assumptions for energy analysis of the studied building.

3.4 Life cycle inventory Energy and raw material inputs for the building products are based on the Ecoinvent database [69]. Process data include the allocated energy use from manufacturing of infrastructure, even though it is supposed to be marginal. Ecoinvent input of wood products includes the solar energy embodied in biomass during its growth, which is equal to the gross heating value of wood [70]. However, the present study does not inventory this input value, as it consists of renewable primary energy resource used as raw materials, as defined by EN 15804 [71] and EN 16485 [72], and has no impact on the production energy of the retrofitting measures.

3.5 System boundaries We analyse the complete life cycle of the retrofitted building elements with the different material alternatives, considering the production, operation, maintenance and end-of-life phases. We calculate the life cycle primary energy as in the equation (1). 𝐸𝑙𝑖𝑓𝑒 𝑐𝑦𝑐𝑙𝑒 = 𝐸𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛 + 𝐸𝑜𝑝𝑒𝑟𝑎𝑡𝑖𝑜𝑛 + 𝐸𝑚𝑎𝑖𝑛𝑡𝑒𝑛𝑎𝑛𝑐𝑒 + 𝐸𝑒𝑛𝑑 𝑜𝑓 𝑙𝑖𝑓𝑒

(1)

3.5.1 Production phase The production energy includes the primary energy used to manufacture, transport and assemble the building materials. The manufacture energy use is calculated based on a bottom up approach by Gustavsson et al. [60], as expressed in equation (2):

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Journal Pre-proof

{ [

𝐿𝑖

]}

𝐸𝑝𝑟𝑜𝑑𝑢𝑐𝑡𝑖𝑜𝑛 = ∑𝑖 ∑𝑘 𝐹𝑖,𝑘(1 + 𝛼𝑘) + 𝜂 + 𝐵𝑖

(2)

where Eproduction is the total primary energy use for material production (kWh); i are the individual types of materials in the building; F is the end-use fossil fuel energy used to extract, process and transport the materials (kWh); k is the type of fossil fuel; α is the fuel cycle energy requirement of the fossil fuel; L is the end-use electricity to extract, process, and transport the materials (kWhe); η is the conversion efficiency for electricity production; B is the heat content of the biomass recovered for energy purposes during material processing (kWh). The fossil fuel energy (F), the biomass (B) and electricity (L) consumption of the building materials are based on Ecoinvent data. But, the primary use of electricity consumption is based on adjusted Ecoinvent data by assuming that coal is used as marginal energy source for the electricity production. The conversion efficiency (η) of coal-fired condensing plants is assumed to be 34.9% [73], while distribution losses for high‐voltage electricity delivered to industrial facilities is assumed to be 2% [74, 75]. The calculation of the material production primary energy takes into account the wastage on the construction site, increasing the amount of materials through the application of the following percentage values from Björklund and Tillman [76]: 7% insulation waste, 10% wood waste, 5% for all other materials. The final quantities of materials are summarized in Figure 1. The primary energy used to transport and assemble building materials is calculated based on average data of 40 kWh/m2 and 80 kWh/m2, respectively, for multi-family buildings in Sweden [77], weighted by the relative primary energy for material production.

3.5.1.1 Bioenergy recovery We assume forest and processing residues to be recovered for energy purposes during the production phase of wood products. The total tree biomass is assumed to be composed of 59% roundwood under bark, 6% bark and 35% branches and tops, excluding stumps and coarse roots, based on Ecoinvent flow data [70]. The amount of roundwood under bark needed to produce sawn timber is calculated based on a breakdown between the end product and processing residue of 51% and 49%, respectively [70]. The manufacturing of boards is based on industrial residual wood and does not produce any biomass residues as co-product. The lower heating values of the processing residues are based on Frischknecht and Jungbluth [78] but adjusted for the Swedish context

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Journal Pre-proof based on [60], resulting in: 3.09 kWh/kg for forest residues, 4.17 kWh/kg for sawing residues and 5.39 kWh/kg for planing residues. The biomass recovery rate is assumed to be 75% for forest residues and 100% for the processing residues. The energy used for recovery and transport of biomass residues is diesel, corresponding to 5% and 1% of the heat value of forest and processing residues, respectively [60]. The relative end-use conversion efficiency between biomass and coal, when biomass replaces fossil coal, is assumed to be 0.98.

3.5.2 Operation phase The operation primary energy includes the full chain to supply the final energy of the building. The heat is provided by the local DHS, which is composed of various heat-only boilers (HOBs), including two wood chip boilers with flue gas condensers, three wood pellet boilers and three oil boilers. The 2013 heat supply was 107 GWh [79]. Oil HOBs are used as a peak-load unit, while wood pellets HOBs as a medium-load unit and wood chips HOBs as base-load unit. The conversion efficiency of the DHS production is assumed to be 90% [79], 108% [79] and 85% [80] for fuel oil, wood chips and wood pellets units, respectively. The distribution network heat loss is assumed to be 10.7% of the overall district heat delivered to the building, based on average value of Swedish district heating systems [81]. Electricity is produced in fossil coal-based marginal power plant and distribution loss is assumed to be 7.7% as the average value for the Swedish electricity network between 2004 and 2013 [81]. The fuel cycle energy inputs of the energy carriers is assumed to be 11% for oil, 3% for wood chips and 11% for wood pellets [82].

3.5.3 Maintenance phase The maintenance primary energy includes the energy use to manufacture, transport and assemble the materials used to replace or renovate worn-out elements throughout their life cycle. The bioenergy recovery from materials’ manufacture is included. The number of times the materials are replaced or the elements are renovated (maintenance cycles) is based on standard service lives for the Swedish residential building stock [83]. Building materials to be maintained and their service lives are: painted aluminium sheet, 50 years; clay tiles, 30 years; painted impregnated sawn timber; 50 years; paint of aluminium parts, 10 years; paint of wood parts, 9 years. The maintenance primary energy is calculated by multiplying the number of maintenance cycles and the production primary energy of each of the materials. In a sensitivity analysis, we repeat the calculation

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Journal Pre-proof reducing the service life of both painted aluminium sheet and painted impregnated sawn timber from 50 to 30 years.

3.5.4 End-of-life phase The net end-of-life energy is calculated as the primary energy used to sort and transport construction and demolition waste (CDW), minus the energy saving from recycling the CDW. The primary energy use for demolition is assumed to be negligible based on [84]. The energy use from landfilling is neglected. The following key factors are taken into account: materials’ end-of-life option, CDW recovery rate and CDW recycling efficiency. The most common recycling options of CDW are considered in order to analyse the potential primary energy benefit.

3.5.4.1 Sorting phase The sorting primary energy use is based on adjusted Ecoinvent data accounting for coal as source of marginal electricity. The energy use for CDW transport in the Ecoinvent data is excluded and instead Swedish haul distances are accounted. Recovery rates of CDW from sorting activities are expected to increase in future, due to technology development and the European waste policies. This study identifies recovery rates based on current and future scenarios. In the current scenario, the overall CDW recovery is about 50%, based on 2012 Swedish statistics [85]. In the future scenario, CDW recovery is assumed to be 95%, an average of the following values in literature: 90% [20], 93% [86], 95% [87] and 100% [Quack, 2001 in 87].

3.5.4.2 Transport phase The recovered waste is delivered to the recycling site, while the remaining and non-recoverable waste is delivered to landfill. Backfill material (i.e. brick waste) is assumed to be crushed at the waste processing site. The transport primary energy use is calculated based on specific haul distances to the nearest recovery/disposal site, assuming the Swedish waste management and production systems, as shown in Table 3. We assumed that transportation occurs by middle-sized truck of 26 tons, travelling full to the plant with a capacity of 70%, consuming 32 l/100 km of diesel fuel, based on NTM Road [2008, in 90]. However, fuel consumption of heavy-duty vehicles is expected to decrease between 41 and 52% by 2030, thanks to

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Journal Pre-proof technology advancements in engine, lightweighting, driver assistance, etc. Therefore, we assume diesel fuel consumption to be 15 l/100km at the time of the building’s demolition. The heating value and the fuel-cycle energy use of diesel are taken to be equal to 35.3 MJ/litre and 9% [82], respectively.

3.5.4.3 Recycling phase We calculate energy benefits from recycling (backfilling included) and energy recovery of waste, as the production primary energy of the substituted primary materials and marginal fossil fuels, respectively. We identify materials’ end-of-life options based on the most common practices and regulations on waste management in Sweden (Table 3). The recycling efficiency rate of aluminium scrap and brick rubble is 96% [96] and 15% [84], respectively, based on average used technology. The recycling efficiency rate of glass and mineral wool waste is 120% [92] and about 9% based on [97], respectively, based on best available technology. We assume glass and mineral wool waste to be recycled only in the future scenario.Wood and XPS waste have a lower heating value of 5.17 [60] and 9.65 kWh/kg [43], respectively. The calculation of energy recovery of wood waste is as described in section 3.5.1.1. XPS waste is assumed to be incinerated in a municipal incineration plant producing electricity with conversion efficiency of 30% [98].

4. Results 4.1 Operation energy saving The operation annual final energy use of the initial building is 271 MWh (136 kWh/m2), including space and tap water heating, and ventilation, and decreases by 171 MWh (86 kWh/m2 or 63%) and 211 MWh (106 kWh/m2 or 78%) in the PH50 and PH30 buildings, respectively, to achieve the passive house standards of 50 kWh/m2 and 30 kWh/m2 final energy use (Table 4). The annual heat saving from the VHR units and improved water taps are 35 and 10 kWh/m2, respectively, together accounting for 52% and 42% of the overall final energy saving in the PH50 and PH30 buildings, respectively. The remaining heat saving is from improved thermal building envelope. Figure 2 shows the profiles of the annual final space heating demands of the initial and retrofitted buildings. The peak space heat demands of the PH50 and PH30 retrofits are 71 and 90% lower compared to the initial building, respectively. The annual primary energy use of the initial building is 399 MWh (199 kWh/m2) and

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Journal Pre-proof decreases by 244 MWh (122 kWh/m2 or 61%) and 303 MWh (152 kWh/m2 or 76%) after the PH50 and PH30 retrofits, respectively, with trends similar to the final energy savings.

4.2 PH50 retrofitting options Table 5 shows the primary energy use of the PH50 retrofitted building parts for the non-operation life cycle phases. The basement and attic floor account for the highest share of the non-operation primary energy, together ranging from 56 to 80%. The lowest share correspond to the retrofitting options with wood fibre insulation and wood-framed windows and the highest share with glass wool insulation and aluminium-framed windows (Figure 3). The non-operation primary energy varies significantly for different insulation materials, with the wood fibre insulation giving 97% lower primary energy use than the glass wool insulation. Different window frame materials give a more moderate variation, as the wood-framed windows has 31% lower nonoperation primary energy use than aluminium-framed windows. The production phase dominates the non-operation energy of the building parts. Notwithstanding, end-of-life primary energy benefit is significant for the burnable materials. End-of-life benefits of XPS and wood fibre account for 7% and 87% of the non-operation energy, respectively. In the windows, primary energy benefits are mainly from the energy recovery of wood waste and the recycling of aluminium. The end-of-life primary energy benefits of windows are 90% and 86% from the wood and aluminium frames, alternatively, while the remaining is from glass recycling. The energy recovery of biomass residues in the production and maintenance phases increases the primary energy benefits of wood-framed windows by up to 48%. The total non-operation primary energy of the retrofitting options ranges between 629 and 1191 MWh, where the low-energy option has wood fibre insulation and wood-framed windows and the high-energy option has glass wool insulation and aluminium-framed windows (Figure 4). Retrofitting options using rock wool insulation result in intermediate non-operation energy values. The total non-operation primary energy follows the trend of the production energy, accounting for between 80 and 92%. The maintenance phase is not significant, ranging from 3 to 4% in the retrofitting options with wood-framed windows and from 5 to 6% in retrofitting options with aluminium-framed windows. The end-of-life primary energy ranges between 3 and 14%, depending on the primary energy benefits from the waste recovery. The end-of-life primary energy is between 0 and -80 MWh, where the highest benefits are from the bioenergy recovery of wood fibre insulation. Bioenergy recovery in production and maintenance phases is significant in wood-framed windows.

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Journal Pre-proof The non-operation primary energy use of total operation primary energy saving ranges between 5 and 10%. The annual net primary energy saving, which is the operation primary energy saving minus the non-operation primary energy use calculated on an annual basis assuming a life span of 50 years, ranges between 222 and 233 MWh (-23 and -12 MWh compared to the total operation energy saving, respectively), depending on the retrofitting options.

4.3 PH30 retrofitting options Table 6 shows the primary energy use of the PH30 retrofitted building parts for the non-operation life cycle phases. The external walls account for the highest share of non-operation primary energy, ranging between 64% and 80%. The breakdown between thermal insulation and cladding depends on the materials. Cladding account for about 90%, 92% and 99.8% of the non-operation energy of the external walls when thermal insulation is glass wool, rock wool and wood fibre, respectively (Figure 5). Windows account for the second highest share of non-operation primary energy, ranging between 9% and 19%, followed by basement walls and attic floor. Thermal insulation in basement walls (i.e. XPS insulation) accounts for 32%, 41% and 96% of the nonoperation primary energy when glass wool, rock wool or wood fibre, respectively, are used. Consistent with the PH50 retrofitting options, the non-operation primary energy linked to the thermal insulation varies significantly, depending on the material, while windows and cladding show moderate variations. The production phase usually dominates the non-operation energy of the building elements, with the exception of cladding. The maintenance primary energy is normally negligible, since minor maintenance interventions are expected, but it accounts for 5%, 12% and 18% of the production energy for wood, brick and aluminium claddings, respectively. The end-of-life primary energy benefits are up to 14%, 7% and 6% of the production primary energy for the wood, aluminium and brick claddings, respectively. These primary energy benefits are from energy recovery of wood, recycling of aluminium and backfilling with brick. The end-of-life primary energy benefit of wood cladding is roughly three and two times greater compared to brick and aluminium claddings, respectively. Although specific primary energy benefit from aluminium recycling (16.5 kWh/kg) is higher compared to energy recovery of wood waste (5.3 kWh/kg), total primary energy benefit from wood cladding is higher compared to aluminium cladding due to the materials quantity.

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Journal Pre-proof In the cladding category, the low-energy option is wood. Bioenergy recovery in the production phase increases the primary energy benefits in wood claddings by up to 80%. Figure 6 shows the total non-operation primary energy of the PH30 retrofitting options. The values range between 1861 and 3129 MWh, where the low-energy option has wood fibre insulation, wood cladding and wood-framed windows and the high-energy option has glass wool insulation, aluminium cladding and aluminium-framed windows. Retrofitting options using rock wool insulation result in intermediate nonoperation energy values with variations depending on the cladding and window frame materials. The total production primary energy ranges between 2231 and 2898 MWh, where the low- and high-energy retrofitting options are consistent with the non-operation primary energy results. The total production primary energy account for between 86% and 95% of the non-operation primary energy use. The total maintenance primary energy is between 119 and 384 MWh, accounting for 5-7%, 9-11% and 12-15% of the net non-operation energy use for the retrofitting options with wood, brick and aluminium cladding, respectively. The total endof-life energy is between -308 and -135 MWh, accounting for 4-8%, 5-9% and 10-17% of the non-operation energy in the retrofitting options with brick, aluminium and wood cladding, respectively. Bioenergy recovery in the production phase gives 10% of the non-operation energy in the wood-maximised option. The non-operation primary energy use of the total operation primary energy saving for the PH30 retrofitting options is between 12% and 21%. The annual net primary energy saving ranges between 241 and 267 MWh (-63 and -37 MWh compared to the total operation energy saving, respectively), depending on the retrofitting options.

5. Sensitivity analysis 5.1 Maintenance cycle of building claddings Our reference building is situated in a normal condition and the service life of the aluminium and wood claddings is expected to be 50 years as the assumed remaining lifetime of the building. However, in exposed conditions, the service life of aluminium and wood claddings might be reduced significantly, resulting in the substitution of worn-out claddings once in the life span of the PH30 retrofitted building. Tables 7 and 8 show the non-operation primary energy use when the building claddings are in exposed condition with a service life of 30 years.

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Journal Pre-proof The maintenance primary energy of aluminium and wood claddings increases by 33% and 40%, respectively, because of the need to produce, transport and assemble new claddings substituting worn-out ones. The changes in maintenance primary energy increase the total non-operation primary energy use of the aluminium- and wood-cladded retrofitting options by 21-27% and 22-29%, respectively. This results in higher non-operation primary energy use of the wood-cladded retrofitting options compared to brick-cladded ones. The non-operation primary energy use of total operation primary energy saving for the PH30 retrofitting options increases by about 21% and 29% for aluminium- and wood-cladded options, respectively.

5.2 Energy supply for retrofitted buildings The effects of changed electricity production from fossil coal to gas in stand-alone plants on the primary energy for non-operation life cycle phases are shown in Tables 9 and 10 for the PH50 retrofitting options and Tables 11 and 12 for the PH30 retrofitting options, respectively. Using fossil gas instead of coal reduces the production and maintenance primary energy use for the building materials, due to the higher conversion efficiency of gasfired plants, assumed to be 44.3% [73]. The estimated primary energy benefits from waste (i.e. XPS) and biomass recovery decrease as these products are assumed to replace fossil gas instead of coal. In the PH50 retrofitting options, the primary energy trend is unchanged. However, the net primary energy use reduces by 3%, 5% and 7% for the retrofitting options with wood fibre, rock wool and glass wool insulation in the attic floor, respectively (Figure 7). In the PH30 retrofitting options, the net primary energy use is reduced by about 8%, 9% and 13% for the aluminium, brick and wood claddings, respectively, when using fossil gas instead of coal based electricity. Claddings account for an average of 80% of the primary energy variation due to the material quantities. Net primary energy use is lower for aluminium and wood claddings than for brick cladding per material quantity, due to the lower energy benefits from the waste recovery when using fossil gas instead of coal electricity. However, the reduction of net primary energy use of the wood cladding is 30% higher if compared to the brick cladding, because of the material quantity (Figure 8).

6. Discussion

15

Journal Pre-proof The results of this study show that the thermal improvement of the building envelope is indispensable to achieve high-energy efficiency standard in retrofitted buildings. Although the operation energy still significantly contributes to the life cycle energy use of both the PH50 and PH30 buildings, the non-operation energy used to retrofit the PH50 and PH30 buildings accounts for 5-10% (8%, on average) and 12-21% (17%, on average) of the operation primary energy saving over a life span of 50 years, respectively. Based on material choice given the highest net primary energy savings, the net primary energy saving of the PH50 and PH30 retrofitting options are 11606 and 13325 MWh, respectively. Using rock or glass wool for insulation instead of wood fibre reduces the net savings by 3 and 4%, respectively for the PH50 option. The corresponding numbers for the PH30 option are 2 and 4%. Based on material choice given the lowest net primary energy savings, the net primary energy saving of the PH50 and PH30 retrofitting options are 11109 and 12070 MWh, respectively. This supports the initial assumption that retrofitting options for existing buildings need to be analysed in a life cycle perspective. Furthermore, the electricity supply system can affect the impact of energyefficient envelope measures significantly. When using electricity from gas-fired, power plant, the net primary energy savings decrease somewhat for the PH30 retrofitting options but are still between 6 and 22% higher compared to the PH50 retrofitting options. The PH30 retrofitting options use up to 2524 MWh more energy in the production and maintenance phases and recover up to 267 MWh more of energy in the end-of-life phase than the PH50 retrofitting options. This is because the PH30 building includes additional retrofitting measures increasing the material quantities for thermal insulation, cladding and windows. In the PH50 retrofitting options, the choice of the attic insulation materials influence the primary energy balances by up to 73%. In the PH30 retrofitting options, cladding materials affect the primary energy balances more than insulation materials, accounting for between 55 and 80% of the non-operation energy. The highest share correspond to the use of aluminium cladding together with wood fibre insulation and wood-framed windows. The production phase accounts for the highest share of life cycle non-operation primary energy use for both the PH50 and PH30 building retrofitting options. In the PH50 options the production energy for insulation materials give the largest net primary energy use, while in the PH30 options the results are variable due to the use of a larger number of materials. In both PH50 and PH30 retrofitting options, a maximum use of wood

16

Journal Pre-proof materials give the lowest net primary energy use. This is due to the low production energy of wood and to the energy recovery of woody biomass from manufacture, construction and demolition activities. The maintenance primary energy is negligible in the PH50 retrofitting options but not for PH30 retrofitting options. Maintenance primary energy mainly depends on the service lives of building elements, especially for cladding materials. For buildings in exposed conditions, the expected service life of aluminium and wood claddings may be shorter than the expected remaining lifetime of the building in contrast to brick cladding. This results in higher primary energy balance also for the wood-cladded options, compared to the brick-cladded options, as shown in the sensitivity analysis. Finally, maximising CDW recovery for recycling or energy purposes gives primary energy benefits. The use of wood-based materials results in wood waste that can be recovered for energy purposes in the production, maintenance and end-of-life-phases. The non-wood materials can be incinerated for energy purposes (e.g. XPS) or recycled. Assuming the most common waste disposal practices for the building materials, the recycling usually gives primary energy benefits, especially for metal scraps. The primary energy benefits from the recovery of inert materials is minor, since the primary energy used to recover clay elements is typically higher than the benefits from the avoided production of primary aggregates. This is mainly because of the energy use for crushing operations and the losses of crushed material [58]. The variations in primary energy use and recovery between the PH50 and PH30 buildings are also dependent on the area of the overall extra-insulation layer and on the surface area to volume ratio. This could be explored by studying different building types. The ratio between non-operation primary energy use and total operation primary energy saving for the PH30 is higher than for the PH50 retrofitting options. However, when comparing the annual net primary energy saving of the PH30 and PH50 retrofitting options, the low-energy PH30 retrofitting option results in 20% higher net primary energy savings than the high-energy PH50 retrofitting option, but the high-energy PH30 retrofitting option has only 3% higher net primary energy savings than the low-energy PH50 retrofitting option.

7. Conclusions Energy retrofit of existing buildings is important for a transition to low energy built environment. Here, the operating primary energy use of the analysed building could be reduced by 12235 and 15186 MWh for the PH50 and PH30 options, respectively, during the expected remaining lifetime of the building of 50 years.

17

Journal Pre-proof Building materials are mostly responsible for the non-operation primary energy use when the thermal envelope is improved. This is consistent with the mentioned Refs [17, 18, 19]. Our results show that the non-operation primary energy use can vary significantly, between 629 and 1191 MWh in PH50 building and between 1861 and 3129 MWh in PH30 building, depending on the choice of materials for thermal insulation, cladding systems and energy-efficient windows. Consequently, the net primary energy savings from building retrofitting can vary significantly, especially in the retrofitted buildings with high energy performance levels, due to the larger amount of materials used for building retrofitting. The estimated net primary energy saving is between 5 and 21%, which is similar to the results of previous studies [16, 17, 18]. Using wood can be decisive to achieve low non-operation primary energy use, especially if biomass residues from wood production are recovered for energy purposes. Furthermore, the impact on the non-operation energy use of retrofitted buildings is largest when wood materials is used in those building parts with the highest material quantity, as building cladding and thermal insulation. Design strategies should pay attention to the durability of building materials to reduce maintenance need. Finally, both the energy recovery of burnable materials and the recycling of non-burnable materials in the end-of-life phase save primary energy and raw material resources. However, the amount of savings from energy recovery and recycling of CDW depends on the technology development and waste policies. The primary energy benefits from the recovery of inert materials is usually minor, since the primary energy used to recover the post-use concrete or clay elements is typically higher than the benefits from the avoided production of primary aggregates. Design for disassembly is a promising approach to improve the recovery rate of CDW. The non-operation primary energy saving due to both energy recovery and recycling of building materials in the end-of-life phase is up to 17%. In summary, a life cycle perspective and good design practices could help select suitable building materials, which are compatible with architectural and technical requirements while minimising non-operation primary energy use.

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Abbreviations PH50

Reference building retrofitted to 50 kWh/m2

PH30

Reference building retrofitted to 30 kWh/m2

CDW

Construction and Demolition Waste

Figures

26

Journal Pre-proof

Basement walls XPS Attic floor Glass wool Rock wool Wood fibre Windows Aluminium Wood External walls Glass wool Rock wool Wood fibre Aluminium Brick Wood 0

5

10

15

20

25

30

35

PH50 building

40

45

50

55

60

65

PH30 building

Figure 1. Quantities (tons) of building materials used in PH50 and PH30 buildings.

SPACE HEAT DEMAND (kW)

70 initial building

60

PH50 building

50

PH30 building

40 30 20 10 0 1 30 59 88 117 146 175 204 233 262 291 320 349 DAY

Figure 2. Annual profiles of final space heat demand of the initial and retrofitted buildings, arranged in descending order.

27

70

Journal Pre-proof 1500 windows attic floor 1000

MWh

basement walls

500

0

Alum. Wood Alum. Wood frame frame frame frame Glass Rockw wool ool

Alum. Wood frame frame Wood fibre

Figure 3. Non-operation primary energy use (MWh) of the PH50 retrofitting options by building part. 1500

maintenance 1191

1000

production 1090

1047

bioenergy recovery 946

end of life

MWh

730

629

total

500

0

-500

Alum. Wood Alum. Wood frame frame frame frame Glass Rockw wool ool

Alum. Wood frame frame Wood fibre

Figure 4. Primary energy use (MWh) of the PH50 retrofitting options by non-operation life cycle phase.

28

Journal Pre-proof external walls - cladding external walls - insulation windows attic floor basement walls

3500 3000

MWh

2500 2000 1500 1000 500 0

Alum. Wood Alum. Wood Alum. Wood Alum. Wood Alum. Wood Alum. Wood Alum. Wood Alum. Wood Alum. Wood frame frame frame frame frame frame frame frame frame frame frame frame frame frame frame frame frame frame Alum. Brick Wood Alum. Brick Wood Alum. Brick Wood claddin claddin claddin claddin claddin claddin claddin claddin claddin g g g g g g g g g Glass Rockw Wood wool ool fibre

Figure 5. Non-operation primary energy use (MWh) of the PH30 retrofitting options by building part.

maintenance production bioenergy recovery end of life total

3500 3000 2500

3129 3026

3000

2915

2897 2465

2812 2785

2362

2682

2604 2256

2000

2501

2474

2371

2153 1964 1861

MWh

1500 1000 500 0 -500 -1000

Alum. Wood Alum. Wood Alum. Wood Alum. Wood Alum. Wood Alum. Wood Alum. Wood Alum. Wood Alum. Wood frame frame frame frame frame frame frame frame frame frame frame frame frame frame frame frame frame frame Alum. Brick Wood Alum. Brick Wood Alum. Brick Wood claddin claddin claddin claddin claddin claddin claddin claddin claddin g g g g g g g g g Glass Rockw Wood wool ool fibre

29

Journal Pre-proof Figure 6. Primary energy use (MWh) of the PH30 retrofitting options by non-operation life cycle phase. 1400

coal fossil gas

1200 1000

MWh

800 600 400 200 0

Alum. frame Glass wool

Wood frame

Alum. Wood frame frame Rockwo ol

Alum. frame Wood fibre

Wood frame

Figure 7. Total non-operation primary energy use (MWh) of the PH50 retrofitting options when using fossil coal or gas electricity.

3500

coal fossil gas

3000 2500

MWh

2000 1500 1000 500 0

Alum. Wood Alum. Wood Alum. Wood Alum. Wood Alum. Wood Alum. Wood Alum. Wood Alum. Wood Alum. Wood frame frame frame frame frame frame frame frame frame frame frame frame frame frame frame frame frame frame Alum. Brick Wood Alum. Brick Wood Alum. Brick Wood claddi claddi claddi claddi claddi claddi claddi claddi claddi ng ng ng ng ng ng ng ng ng Glass Rock Wood wool wool fibre

Figure 8. Total non-operation primary energy use (MWh) of the PH30 retrofitting options when using fossil coal or gas electricity.

30

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Tables Table 1. Comparison of different passive house standards applicable in Sweden. Description

Unit

FEBY12 (2012)

Wahlström et al. (2008)

kWh/m2, year

≤ 50

≤ 45

≤ 25

-

Evv* =Vvv**55

Evv* =Vvv**55

30

-

PHI (2016)

Final energy use Energy use for heating Energy use for hot water (included in

≤ 30

kWh/m2, year ‘Energy use for heating’) kWh/m2, year

Household electricity

-

* Standardised annual energy use for hot water. ** Annual volume of used hot water.

Table 2. Adopted thermal envelope improvements for different passive house levels. Thermal improvement

Unit

Initial building

PH50 building

PH30 building

Insulation - attic

mm

0

+540/600*

+280/360*

Insulation - walls

mm

0

0

+160/170*

Insulation – basement

mm

0

+290

+190/200*

W/m2K

2.9

0.8

0.6

Energy-efficient windows

* The insulation thickness varies within the range depending on the insulation material.

Table 3. Haul distances and end-of-life options assumed for each construction and demolition waste. Construction and demolition waste

Transport phase

Recycling phase

Haul distance [km]

References

End-of-life option

References

Aluminium

100

[88]

recycle

[88]

Brick

10

[89]

backfill

[91]

Glass*

1000

Based on European production sites.

landfill, recycle

[91]; [92]

Mineral wool*

200

Based on Swedish production sites.

landfill, recycle

[91]; [93]

Wood

90

[89]

energy recovery

[91]; [94]

XPS

90

[89]

energy recovery

[95]

* Materials expected to be recycled in the future scenario.

31

Journal Pre-proof Table 4. Final and primary operation energy use in MWh per year (in brackets kWh per m2 heated floor area and year) of the initial building and final and primary operation energy saving in MWh per year (in brackets kWh per m2 heated floor area and year) of the PH50 and PH30 buildings. Initial building

Description

PH50 building

PH30 building

Final energy

Primary energy

Final energy

Primary energy

Final energy

Primary energy

use

use

saving

saving

saving

saving

Space heat

216 (108)

314 (157)

-153 (-77)

-221 (-111)

-193 (-97)

-280 (-140)

Tap water

50 (25)

70 (35)

-20 (-10)

-28 (-14)

- 20 (-10)

-28 (-14)

Ventilation

6 (3)

15 (7)

2 (1)

5 (2)

2 (1)

5 (2)

271 (136)

399 (199)

-171 (-86)

244 (-123)

-211 (-106)

303 (-152)

Total

Table 5. Primary energy use (MWh) of the PH50 building parts by non-operation life cycle phase. Production

Maintenance

End of life

Bioenergy recovery

Total

398

25

-27

0

396

Glass wool

473

0

0

0

473

Rock wool

329

0

0

0

329

Wood fibre

92

0

-80

0

12

Aluminium

306

30

-15

0

321

Wood

256

8

-20

-23

220

Basement walls XPS Attic floor

Windows

Table 6. Primary energy use (MWh) of the PH30 building parts by non-operation life cycle phase. Production

Maintenance

End of life

Bioenergy recovery

Total

XPS (with glass wool)*

225

25

-14

0

236

XPS (with rock wool)*

213

25

-13

0

225

XPS (with wood fibre)*

213

25

-13

0

225

Basement walls

Attic floor

32

Journal Pre-proof Glass wool

283

0

0

0

283

Rock wool

170

0

0

0

170

Wood fibre

49

0

-43

0

6

Aluminium

352

30

-15

0

368

Wood

300

8

-20

-23

265

Glass wool

218

0

0

0

218

Rock wool

157

0

0

0

157

Wood fibre

41

0

-37

0

4

Aluminium (with glass wool)*

1819

328

-123

0

2024

Aluminium (with rock wool)*

1793

328

-126

0

1995

Aluminium (with wood fibre)*

1794

328

-121

0

2001

Brick (with glass wool)*

1785

216

-106

0

1895

Brick (with rock wool)*

1757

216

-108

0

1865

Brick (with wood fibre)*

1759

216

-104

0

1871

Wood (with glass wool)*

1660

86

-225

-161

1360

Wood (with rock wool)*

1627

86

-220

-157

1336

Wood (with wood fibre)*

1628

86

-196

-157

1361

Windows

External walls Insulation

Cladding

* The selected insulation materials in the external walls and their corresponding thermal performance influence the quantity, as well as the primary energy use, of the materials in the basement walls and the cladding.

Table 7. Non-operation primary energy use (MWh) of the PH30 building claddings with a service live of 30 years for aluminium and wood claddings. Production

Maintenance

End of life

Bioenergy recovery

Total

Aluminium (with glass wool)

1819

1046

-173

0

2693

Aluminium (with rock wool)

1793

1045

-178

0

2660

Aluminium (with wood fibre)

1794

1045

-171

0

2669

Wood (with glass wool)

1660

823

-335

-250

1898

Wood (with rock wool)

1627

822

-330

-246

1874

Cladding

33

Journal Pre-proof Wood (with wood fibre)

1628

822

-305

-246

1900

Table 8. Total non-operation primary energy use (MWh) of the PH30 retrofitting options with a service live of 30 years for aluminium and wood claddings. Basement walls

Attic floor

Windows

External walls

Total

Insulation

Insulation

Window frame

Insulation

Cladding

XPS

Glass wool

Aluminium

Glass wool

Aluminium

3797

XPS

Glass wool

Aluminium

Glass wool

Wood

3002

XPS

Glass wool

Wood

Glass wool

Aluminium

3694

XPS

Glass wool

Wood

Glass wool

Wood

2899

XPS

Rock wool

Aluminium

Rock wool

Aluminium

3580

XPS

Rock wool

Aluminium

Rock wool

Wood

2794

XPS

Rock wool

Wood

Rock wool

Aluminium

3477

XPS

Rock wool

Wood

Rock wool

Wood

2691

XPS

Wood fibre

Aluminium

Wood fibre

Aluminium

3272

XPS

Wood fibre

Aluminium

Wood fibre

Wood

2503

XPS

Wood fibre

Wood

Wood fibre

Aluminium

3169

XPS

Wood fibre

Wood

Wood fibre

Wood

2400

Table 9. Primary energy changes (MWh) of the PH50 building parts when changing from fossil coal to gas electricity, by non-operation life cycle phase. Production

Maintenance

End of life

Bioenergy recovery

Total

-11

-3

6

0

-9

Glass wool

-48

0

0

0

-49

Rock wool

-16

0

0

0

-16

Wood fibre

-8

0

16

0

8

Aluminium

-21

-1

0

0

-23

Wood

-28

-1

4

5

-20

Basement walls XPS Attic floor

Windows

34

Journal Pre-proof Table 10. Total non-operation primary energy changes (MWh) of the PH50 retrofitting options when changing from fossil coal to gas electricity. Basement walls

Attic floor

Windows

Total PE

Insulation

Insulation

Window frame

XPS

Glass wool

Aluminium

-81

XPS

Glass wool

Wood

-78

XPS

Rock wool

Aluminium

-48

XPS

Rock wool

Wood

-45

XPS

Wood fibre

Aluminium

-24

XPS

Wood fibre

Wood

-21

Table 11. Primary energy changes (MWh) of the PH30 building parts when changing from fossil coal to gas electricity, by non-operation life cycle phase. Production

Maintenance

End of life

Bioenergy recovery

Total

XPS (with glass wool)

-7

-3

3

0

-7

XPS (with rock wool)

-7

-3

3

0

-7

XPS (with wood fibre)

-7

-3

3

0

-7

Glass wool

-29

0

0

0

-29

Rock wool

-9

0

0

0

-9

Wood fibre

-5

0

9

0

4

Aluminium

-27

-1

1

0

-27

Wood

-33

-1

4

5

-25

Glass wool

-22

0

0

0

-22

Rock wool

-8

0

0

0

-8

Wood fibre

-4

0

8

0

4

Aluminium (with glass wool)

-180

-14

3

0

-191

Aluminium (with rock wool)

-178

-14

3

0

-189

Basement walls

Attic floor

Windows

External walls Insulation

Cladding

35

Journal Pre-proof Aluminium (with wood fibre)

-178

-14

3

0

-189

Brick (with glass wool)

-174

-13

2

0

-185

Brick (with rock wool)

-171

-13

2

0

-182

Brick (with wood fibre)

-171

-13

2

0

-182

Wood (with glass wool)

-316

-4

46

33

-241

Wood (with rock wool)

-310

-4

45

32

-237

Wood (with wood fibre)

-310

-4

40

32

-242

Table 12. Total non-operation primary energy changes (MWh) of the PH30 retrofitting options when changing from fossil coal to gas electricity. Basement walls

Attic floor

Windows

External walls

Insulation

Insulation

Window frame

Insulation

Cladding

XPS

Glass wool

Aluminium

Glass wool

Aluminium

-276

XPS

Glass wool

Aluminium

Glass wool

Brick

-270

XPS

Glass wool

Aluminium

Glass wool

Wood

-326

XPS

Glass wool

Wood

Glass wool

Aluminium

-274

XPS

Glass wool

Wood

Glass wool

Brick

-268

XPS

Glass wool

Wood

Glass wool

Wood

-324

XPS

Rock wool

Aluminium

Rock wool

Aluminium

-240

XPS

Rock wool

Aluminium

Rock wool

Brick

-233

XPS

Rock wool

Aluminium

Rock wool

Wood

-288

XPS

Rock wool

Wood

Rock wool

Aluminium

-238

XPS

Rock wool

Wood

Rock wool

Brick

-231

XPS

Rock wool

Wood

Rock wool

Wood

-286

XPS

Wood fibre

Aluminium

Wood fibre

Aluminium

-215

XPS

Wood fibre

Aluminium

Wood fibre

Brick

-208

XPS

Wood fibre

Aluminium

Wood fibre

Wood

-268

XPS

Wood fibre

Wood

Wood fibre

Aluminium

-213

XPS

Wood fibre

Wood

Wood fibre

Brick

-206

XPS

Wood fibre

Wood

Wood fibre

Wood

-266

36

Total

Journal Pre-proof Highlights  Life-cycle primary energy use when retrofitting an existing building is analysed.  Life-cycle primary energy use depends on the passive house standard to achieve.  Materials used in energy-retrofitted buildings affect net primary energy savings.

1