LCA from cradle-to-cradle of energy-related building assemblies: Promoting eco-efficient materials

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1 LCA from cradle-to-cradle of energy-related building assemblies: Promoting eco-efficient materials José D. Silvestre Department of Civil Engineering, Architecture and Georesources (DECivil), Instituto Superior Técnico (IST), Universidade de Lisboa (UTL), Lisbon, Portugal Jorge de Brito DECivil, IST, UL, Lisbon, Portugal Manuel D. Pinheiro DECivil, IST, UL, Lisbon, Portugal ABSTRACT: This paper presents a methodology for the Life Cycle Assessment (LCA) of energy-related building assemblies that promotes solutions that use eco-efficient materials. This methodology allows the environmental, energy and economic (3E) LCA from cradle to cradle (3E-C2C) in accordance with European standards. 3E-C2C includes 3E cost-c2c, which enables the quantification of all aspects of performance in the same unit. 3E-C2C was applied to 60 external wall alternatives, considering its location in a building in Portugal and using mainly site-specific data for the 16 materials considered. It was found that 3E-C2C allows the characterisation of the benefits and loads of these materials in a clear and quantitative manner. These impacts are expressed in each dimension of performance and lifecycle stage (e.g. production, transportation to site, installation, use stage, and end-of-life), allowing eco-efficient materials to be identified and promoted due to their higher performance. 1. INTRODUCTION This paper presents a methodology for the Life Cycle Assessment (LCA) of energy-related building assemblies, which was applied to 60 alternatives for external walls of buildings. The results show that this methodology rewards the use of eco-efficient materials by characterising their benefits and loads in each dimension of performance and life-cycle stage. 2. METHOD - 3E-C2C ASSESSMENT The approach applied allows an assessment of the environmental, energy and economic (3E) life cycle performance from cradle to cradle (3E-C2C) in accordance with European standards (Silvestre 2012). 3E-C2C allows the appraisal, comparison and selection of energy-related building assemblies and was applied to 60 current solutions for external walls of buildings Scope - system boundaries The 3E-C2C approach is defined from cradle-to-cradle, including the life cycle stages of construction products already standardised (see Table 1 - including the extraction and processing of raw materials and the production, the transport, distribution and assembly, use, maintenance and final disposal (CEN 2011b, CEN 2012b). The 3E-C2C approach therefore includes the life cycle stages and/or processes affected by the external walls (i.e. material production and transport, heating and cooling, and maintenance operations), but does not include the 3E impacts of activities during the use stage that are not affected by the exterior wall solution. 837

2 Portugal SB13 - Contribution of Sustainable Building to Meet EU Targets 2.2. Scope - declared unit The declared unit was defined as a square meter of external wall for 50 years, taking into account the use and end of life stages and the reference service life of each alternative. A declared unit, instead of a functional equivalent (CEN 2012b), allows the designer to compare two or more assemblies with selection of the best one, even if they are not functionally equivalent (e.g. external walls with different heat transfer coefficients) Scope - case study The model building called Hexa has five residential floors and represents the most common constructive and architectural practices in Portugal. The subject of the study is the flat on the right from an intermediate floor with no building next to the east façade (Figure 1). The location chosen for Hexa was Lisbon, because it is the national metropolitan area with the highest building density. The external walls studied are on the north and south façades (the east façade is considered to be the same for all alternatives). The reference study period was set at 50 years (Silvestre 2012). Table 1 - Impacts and life-cycle stages in each module of the 3E-C2C approach Life cycle stages 3E-C2C Use stage End-of-life stage - transport, module - Product Transportation Installation in Energy use for Maintenance, repair and replace- C4), and reuse, recovery processing and disposal (C2- assembly stage to the building the building heating and performance (A1-A3) site (A4) (A5) cooling (B6) ment (B2-B4) and/or recycling potential (D) Environmental LCA Economic Market acquisition cost - Energy - Costs in the study period Costs (in the study period for B2-B4, and in year 50 for C2-C4 and D) - Figure 1 - Hexa design drawing of a middle floor: the subject of the study is the flat on the right, with no building next to the east façade 2.4. Environmental performance of each wall The environmental performance quantification of the 3E-C2C method follows the LCA standard method (ISO 2006c, ISO 2006d) and most principles included in standards EN :2011 (CEN 2011a) and FprEN 15978:2011 (CEN 2011b), and includes eight impact categories (using CML 2001 baseline - version 2.05) and the life cycles stages described in Table Product stage (A1-A3) The LCA of the production of the majority of the construction materials (cradle-to-gate approach) resulted from studies completed in national plants (12 out of 16 (Silvestre 2012)) and was performed using SimaPro software. In the remaining analyses the NativeLCA methodology was applied in the selection of LCA data sets to be used as generic in the Portuguese context Construction process stage (A4-A5) The construction stage includes (CEN 2012b): the transportation from the production gate to the construction site (A4); the on-site storage of products, the waste of construction products and the processing of product packaging and product waste (A4-A5); and the installation of the product in the building (A5). The 3E-C2C method considers the environmental impacts of all 838

3 these activities, except any energy or water required for installation or operation of the construction site due to their variable and unpredictable nature Use stage - maintenance, repair and replacement (B2-B4) This stage concerns the quantification of the environmental impacts of the materials used in maintenance, repair and replacement operations over the life cycle of the assembly (in the year that they occur) and the frequency of the maintenance work considered in the environmental and economic module is identical. The default value for the reference study period was the required service life of the building, and the estimated service life of each materials took into account the rules and guidance of ISO ,-2,-7 and -8 (ISO 2006a, ISO 2000, ISO 2001, ISO 2006b) Use stage - energy performance (B6) The needs of energy for heating and cooling during a building s operation were calculated according to the national regulations for Energy and indoor air quality certification in buildings (RCCTE 2006), which transposes the EPBD (EC 2002), and are the only operational impacts and cost that are meaningful for the assessment of an external wall alternative. To estimate the environmental impacts of the consumption of energy for heating and cooling, the energy needs of the flat (in kwh; see a detailed description of this calculation procedure in section 2.6.3) by year of the study period were divided by the area of the external wall under evaluation (40.27 m 2 ) to yield a value related to the declared unit used. This value (in kwh), times the number of years of the study period, was then inputted in SimaPro and the environmental impacts were calculated considering a process to model the domestic consumption for heating/cooling at the use stage that represents an updated Portuguese electricity mix (data from 2011) End of life stage (C) and Benefits and loads beyond the system boundary (D) At this stage deconstruction was considered to estimate the environmental and economic impacts of transporting and disposing of Construction and Demolition Wastes (CDW) in suitable sites. The cost and the environmental impacts of transporting and disposing of the CDW generated were based on Portuguese case studies that used waste operators and market prices data E cost-c2c assessment The 3E cost-c2c method includes an environmental impact assessment method (EIAM) with a weighting step that converts the results of all LCA impact categories into an economic unit. This enables the cost of the environmental impacts to be added to the economic and energy whole-life cost, resulting in an overall single score. This EIAM - Eco-costs is a prevention based single indicator for environmental burdens, whose economic unit is the euro (TUDelft 2011). Cev corresponds to the application of the EIAM Eco-costs to the LCA results for each life cycle stage Economic performance of each assembly The whole-life cost (WLC) method (ISO 2008) and most of the principles of EN :2012 (CEN 2012a) were followed, in order to apply the net present value (NPV) method for each alternative. NPV corresponds to the WLC converted to its present value (using a discount rate), and is comparable to all solutions in the year 0, corresponding to the design phase (Silvestre 2012). The NPV of the declared unit of each alternative was calculated for the study period using equation (1) (Table 2), assuming constant prices (ISO 2008) Product and construction process stages (A1-A5) The economic cost in year n per square meter of external wall - Cec n - includes, before the use stage, the market acquisition cost in year 0, which was mostly provided by companies, but obtained also through market surveys, construction firms and building materials suppliers, and based on reference national documents (Silvestre 2012) Use stage - maintenance, repair and replacement cost (B2-B4 The economic cost in year n per square meter of external wall - Cecn - includes the 839

4 Portugal SB13 - Contribution of Sustainable Building to Meet EU Targets maintenance, repair and replacement operation costs incurred in that year, which were provided and obtained similarly to market acquisition costs Use stage - energy cost (B6) The energy cost in year n per square meter of external wall - Ceg n - corresponds to the energy use expenditure on heating and cooling, calculated by the method described in the national regulations (RCCTE 2006) and in equation (2) (Table 2) End-of-life stage (C and D) The economic costs in year 50, i.e. end-of-life costs, include only transportation and disposal costs (gate cost or tipping fee) of the building assemblies and expenses and/or revenues from reuse, recycling, and energy recovery, using the approach described in section Table 2 - Equations (1) and (2) Equation Unit List of abbreviations 50 Cn (1) NPV = n n= 0 (1 + d) (3%). Nic Nvc Aap ( /year*m 2 (2) Cegn = 0.1 T ( + ) of external ηi ηv Aew wall) ( /m 2 ) - C n : cost in year n ( /m 2 ); - d: real discount rate (without considering risk) applied T: cost of 1 kwh of electricity in Portugal for household consumers, without VAT or standing charges ( /kwh) (0.139 /kwh considering an installation of more than 2.3 kva ); Nic: nominal annual heating needs per square meter of net floor area of the flat (kwh/m 2 *year); η i : nominal efficiency of the heating equipment (1, considering the reference value (RCCTE 2006)); Nvc: nominal annual cooling needs per square meter of net floor area of the flat (kwh/m 2 *year); η v : nominal efficiency of the cooling equipment (3, considering the reference value (RCCTE 2006)); Aap: net floor area of the flat under assessment ( m 2 ); Aew: total area of the external wall being assessed (40.27 m 2 ). 3. RESULTS AND DISCUSSION 3E-C2C was applied to 60 common solutions for external walls of buildings, considering single-leaf walls with internal or external insulation and cavity walls, and including 16 components (six thermal insulation materials, two elements of the wall structure, five external claddings and three types of internal coatings). A summarised characterisation of the outer wall alternatives is shown in Table Environmental performance and NPV of the environmental cost (Cev) C2C of the 60 alternatives Table 3 shows the extreme results: C2C (stages A1-A5; B2-B4; C2-C4 and D) in environmental category GWP (Global Warming potential, chosen from the eight impact categories considered in the 3E-C2C method); of the potential environmental cost (Cev, referenced as environmental cost hereafter). Figure 2 presents the potential environmental cost (Cev, by the differences in percentage for W1) of single-leaf walls for stages A1-A3, A4 and B2-B Economic performance C2C and energy performance The extreme results of the NPV of the economic (Cec) and energy (Ceg) costs (with no weighting or aggregation) are characterised in Table 5. Figure 3 shows the Environmental cost (Cev) C2C (stages A1-A5; B2-B4; B6; C2-C4 and D), Economic cost (Cec) C2C (stages A1-A5; B2-B4; C2- C4 and D) and Energy cost (Ceg) of cavity walls (by the differences in for W1) Discussion of results Table 3 shows that the solution with the lowest environmental impacts at product stage (W29 - Figure 2; and W43 on its group of walls) and with the lowest GWP C2C reflects the improved 840

5 environmental performance of ICB boards in comparison with alternative insulations. The low environmental cost of production and the recycling potential of these boards (namely of on-site ICB wastage) also benefits W3, the solution with the lowest C2C environmental cost. Nevertheless, the high weight of ICB boards sent to landfill, and corresponding transport and disposal, when applied on a VRF system, defines W13 as the solution with the highest end-of-life environmental costs (and W29 on its group of walls). The potential reuse on-site of LWA, and the lower weight of claddings that are transported and disposed of into landfill, places W40 at the other extreme at the same stage (and also in terms of economic cost - Table 5). Local materials influence the environmental performance of the walls at A4 stage, making W2 the best solution due to the shorter distance of the production plant of stabilized mortar used as render (Table 3 and Figure 2; and also due to the lower weight of EPS boards in comparison with the remaining insulation materials). The production of one-coat mortar and gypsum plasterboard in a farther place makes, on the other hand, W26 the solution with the highest environmental costs at this stage (Table 3 and Figure 2). Due to the lower waste production on installation (by using only one block and dispensing insulation boards) W23 and W24 present the lowest environmental costs at this stage (Table 3). Table 3 Lowest/best and highest/worst (shaded) results per group and overall (*): of the potential environmental cost (Cev); and C2C (stages A1-A5; B2-B4; C2-C4 and D) in GWP (in italic) Group of Life cycle stages (see Table 1) walls A1-A3 A4 A5 B2-B4 C2-C4, and D W3* C2C W2* (shorter distance to W6, W7 and W9 (lower construction site from the W3 (low environmental W21* environmental impacts of the place of production of cost of production and high and disposal in landfill - and/or W3 stabilised mortar used as environmental benefits of W22* lower weight - of SW, EPS render; shorter distance to the disposal - wood recycling - (GFRC and PUR boards and gypsum construction site and lower of on-site ICB wastage) panels) plasterboard as internal weight of EPS boards) cladding) Single leaf walls with external insulation Single leaf walls with internal, and without (W23- W26), insulation Cavity walls W22* C2C W22* (GFRC panels) W21 and W22 (high weight of GFRC panels) W29 C2C; W29* C2C W29* (ICB board) W21* and W22* (manufacture and transportation of ancillary materials, i.e. EPS boards, adhesive mortar, metallic accessories and sealants) W28 and W30 (lower weight W23* and W24* (lower and shorter transportation quantity of construction distances of the insulations wastes) products) W26 C2C (production and transport of claddings from a farther place) W26* (production and W32 (high weight of SW transport of claddings - one- mortar and gypsum wastage that has to be W23-W26coat transported to landfill and plasterboard - that are disposal impacts) produced in a farther place) W48 C2C; W37 C2C W37 and W38 (recycling W43 W42 to W45 (shorter of stabilised mortar (ICB distance to construction site wastage, inexistence of board in from the place of production packaging from this the of internal and external product to be processed cavity) cladding) and reuse on-site of LWA) (W11 to W20)* W13* (weight of the woodplastic extruded boards with (woodplastic ICB boards sent to landfill, extruded and corresponding transport boards in and disposal) the VRF system) W56 at A1-A3 (high environmental impacts of the production of SW boards), and C2C W40 (higher weight and/or W51 (high weight of SW longer transportation wastage that has to be distances of the transported to landfill and corresponding claddings and to the corresponding insulation) disposal impacts) W24 and W26 (lower weight of the gypsum plasterboard that is sent to landfill) W29 (high weight of ICB boards that are sent to landfill, and corresponding environmental impacts in transportation and disposal) W40* (reuse on-site of LWA and lower weight of claddings that are transported and disposed of into landfill) W41, W42, W44, W45 and W51 (high weight of claddings - and of SW board in W41 and W51 - that are transported and disposed of into landfill) 841

6 Portugal SB13 - Contribution of Sustainable Building to Meet EU Targets Table 4 - Outer walls: W1-W22 (Single-leaf walls - External insulation), W23-W26 (Single-leaf walls, no insulation), W27-W36 (Single-leaf walls - Internal insulation), W37-W40 (Cavity walls - Thermal insulation completely filling the cavity); W41-W60 (Cavity walls - Thermal insulation partially filling the cavity) Mats. External wall W W1 W2 W3 W4 W5 W ECS1 x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x ECS2 x x x x x x x x x x x x x x x x x x x ECS3 x x x x x x x x x x ECS4 ECS5 ICS1 x x x x x x x x x x x x x x x x x x x x ICS2 x x x x x x x x x x x x x x x x x x x x x x x x x ICS3 x SW EPS ICB PUR XPS LWA 8 CHB 15 x x CHB 22 CHB LCB 38 x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x x Notes: - External cladding systems (ECS): ECS1 - Adherent (0.02 m render and water-based paint); ECS2 - One-coat mortar; ECS3 - Adherent [0.02 m render, adhesive, (insulation), glass fibre mesh, 0.01 m render and water-based paint] within an ETICS (External Thermal Insulation Composite System); ECS4 - Fastened to a supporting structure - VRF (Ventilated Rainscreen Façades m render in the outer surface of the CHB, and WPC (Wood-plastic composite) structure and boards creating a ventilated cavity); ECS5 - GFRC (Glass Fibre Reinforced Concrete) precast panels with 12 cm EPS boards as void formers; - Internal cladding systems (ICS): ICS1 - see ECS1; ICS2 - Adherent to the wall structure (adhesive, gypsum plasterboards and water-based paint); ICS3 - Adherent to the insulation material [adhesive, (insulation), gypsum plasterboards and water-based paint]; - Insulation materials (the number is the thickness in cm) - EPS (Expanded Polystyrene), ICB (Insulation Cork Board), LWA (Light Expanded Clay Aggregate), PUR (Polyurethane), SW (Stone wool) and XPS (Extruded Polystyrene); - Elements of the wall structure (plus stabilised masonry mortar; the number is the thickness in cm) - CHB (Hollow fired-clay bricks, horizontally perforated), LCB (Lightweight - with LWA - concrete blocks, vertically perforated), and CHB (cavity wall, plus internal 0.02 m render). 842

7 The improved thermal resistance of GFRC panels explains W21 and W22 s lower energy cost (Table 5). The lower thermal resistance of LWA makes W37 the worst solution at this stage (Table 5 and Figure 3). The use of insulating GFRC panels leads to extreme benefits or loads depending on the life cycle stage: their high environmental production cost makes W22 the worst solution at this stage (Table 3 and Figure 2) and C2C; their high weight influence the bad performance of W21 and W22 on the environmental cost of transportation to site (Table 3 and Figure 2); their high need of ancillary materials makes W21 and W22 the worst solutions on the environmental cost of installation (Table 3; and also in terms of economic cost - Table 5); and the high cost of transportation and disposal in landfill of these panels defines W21 as the solution with the highest economic cost at this stage (Table 5). Nevertheless, the lower maintenance needs of these panels provide W21 and W22 with the lowest environmental cost at this stage (Figure 2; and also in terms of economic cost - Table 5). Conversely, the lower durability of wood-plastic extruded boards in the VRF system used in W11 to W20 causes their higher environmental cost at this stage (Figure 2; and also in terms of economic cost - Table 5). The high market acquisition cost of these boards leads to the worst position of W15 at this stage and in terms of economic cost C2C (Table 5). The lower cost of EPS boards places W33 at the other extreme in these two classifications (Table 5). W2 W3 W4 W5 W6 W7 W8 W9 W10 W11 W12 W13 W14 W15 W16 W17 W18 W19 W20 W21 W22 W23 W24 W25 W26 W27 W28 W29 W30-65% -15% 35% 85% 135% A1-A3 - Production environmental impacts A4 - Transport to site environmental impacts B2-B4 - Costs of maintenance, repair and replacement in the study period Figure 2 - Potential environmental cost (Cev) of single-leaf walls for stages A1-A3, A4 and B2-B4 (differences in percentage for W1) W37 W38 W39 W40 W41 W42 W43 W44 W45 W46 W47 W48 W49 W50 W51 W52 W53 W54 W55 W56 W57 W58 W59 W Environmental cost - Total 2.Economic cost - Total 3.Energetic cost Figure 3 - Environmental cost (Cev) C2C (stages A1- A5; B2-B4; B6; C2-C4 and D), Economic cost (Cec) C2C (stages A1-A5; B2-B4; C2-C4 and D) and Energy cost (Ceg) of cavity walls (differences in for W1) 843

8 Portugal SB13 - Contribution of Sustainable Building to Meet EU Targets Table 5 - Lowest/best and highest/worst (shaded) results per group and overall (*): NPV of the economic (Cec) and energy (Ceg; at B6 stage) costs Group of walls Life cycle stages (see Table 1) B2-B4 (economic costs) B6 (energy costs) C2-C4, and D (economic costs) W7 at A1-A5 (Market acquisition cost in year 0) and C2C Single leaf W21* and W22* W19 (lower volume of insulation material that is W21* and W22* (GFRC panels) walls with (GFRC panels) transported to landfill) external W15* at A1-A5 (wood-plastic extruded boards in the corresponding VRF system) and C2C insulation (W11 to W20)* (wood-plastic (cost of transportation and disposal in W1 to W3, W6 to W8W21* extruded boards in the VRF system) landfill of its heavy claddings) Single leaf W33* at A1-A5 and C2C (lower cost of EPS) walls with W35 (lower volume of insulation material that is W23 to W26 W23 to W26 internal, and transported to landfill) without W31 at A1-A5 and C2C (W23-W26), W27 to W29, W32 to W23 (cost of transport and disposal in landfill of W27 to W36 insulation W34 its heavier claddings) Cavity walls W57 at A1-A5 and C2C W44, W49, W54 and W41-W60 W59 W44 at A1-A5 and C2C; W45 C2C W37* (LWA filling W41-W60 the whole cavity) W40* (reuse on-site of LWA and sending less demolition waste from claddings to landfill) W41 (SW boards were the only insulation material that was considered to be sent to landfill) 4. CONCLUSION This paper presents a methodology - 3E-C2C - that rewards the use of eco-efficient materials in energy-related building assemblies by highlighting their environmental benefits and loads in each dimension of performance (3E - environmental, energy and economic) and life-cycle stage. The result of the application of 3E-C2C to 60 external wall solutions showed that the ecoefficient (3E) performance of materials can derive from their: low production environmental impacts, cost or maintenance needs; high durability or thermal insulation; recyclability; local production. These conclusions were based on the individual analysis of the contribution of six thermal insulation materials, two elements of the wall structure, five external claddings and three internal coatings, mostly using site-specific data. In conclusion, from the extensive sample analysed it was possible to confirm the benefits of using 3E-C2C in the design of energy-related building assemblies to reward solutions with eco-efficient materials. 5. ACKNOWLEDGEMENTS The authors thankfully acknowledge the scholarship of FCT (Foundation for Science and Technology) to support the PhD study of the first author and the support of the ICIST Research Institute from IST, Technical University of Lisbon. Special thanks are due to the Portuguese manufacturers for providing the necessary data to complete this research work. REFERENCES CEN 2011a. Sustainability of construction works - Assessment of buildings - Part 2: Framework for the assessment of environmental performance. EN Brussels, Belgium: Comité Européen de Normalisation. CEN 2011b. Sustainability of construction works - Assessment of environmental performance of buildings - Calculation method. FprEN Brussels, Belgium: Comité Européen de Normalisation. CEN 2012a. Sustainability of construction works - Assessment of buildings - Part 4: Framework for the assessment of economic performance. EN Brussels, Belgium: Comité Européen de Normalisation. 844

9 CEN 2012b. Sustainability of construction works - Environmental product declarations - Core rules for the product category of construction products. EN Brussels, Belgium: Comité Européen de Normalisation. EC Directive 2002/91/EC of the European Parliament and of the Council of 16 December 2002 on the energy performance of buildings (EPBD). European Commission. ISO Buildings and constructed assets - Service life planning - Part 1: General principles. ISO :2000. International Organization for Standardization. ISO Building and construction assets - Service life planning - Part 2: Service life prediction procedures. ISO :2001. International Organization for Standardization. ISO 2006a. Buildings and constructed assets - Service life planning - Part 7: Performance evaluation for feedback of service life data from practice. ISO :2006. International Organization for Standardization. ISO 2006b. Buildings and constructed assets - Service life planning - Part 8: Reference service life and service-life estimation. ISO/DIS :2006. International Organization for Standardization. ISO 2006c. Environmental management - Life cycle assessment - Principles and framework. ISO 14040:2006(E). International Organization for Standardization. ISO 2006d. Environmental management - Life cycle assessment - Requirements and guidelines. ISO 14044:2006(E). International Organization for Standardization. ISO Buildings and constructed assets - Service life planning - Part 5: Life-cycle costing. ISO :2008. International Organization for Standardization. RCCTE Regulation of the characteristics of thermal behaviour of buildings (in Portuguese). Silvestre, J. D Life Cycle Assessment from cradle to cradle of Building Assemblies - application to external walls. Ph.D. thesis in Civil Engineering, Instituto Superior Técnico, Technical University of Lisbon. TUDelft The Model of the Eco-costs / Value Ratio (EVR): An LCA based decision support tool for the de-linking of economy and ecology [Online]. Available: [Accessed ]. 845