Chapter 4: Research Methodology
4.3.1 Process-LCA methodology
The methodology has been carried out in accordance with: ISO 14040 (2006) - Environmental Management- life cycle assessment-Principles and framework; and ISO 14044 (2006) - Environmental Management- life cycle assessment- Requirements and Guidelines. It should be noted that the ISO 14040, 41, 42 and 43 were ‘rolled up’ into the above two standards. This section now discusses the process LCA methodology used in study.
136 Functional unit
On the basis of the literature review of studies on functional unit in Chapter 2, two functional units are proposed in this study: the functional unit ‘1 m2 total heated floor area’ is chosen as the most adequate functional unit to compare the results of the LCA because it makes comparison with the results of other studies possible, and in particular it is the functional unit used in most studies. The functional unit of study represents the use of 1 m2 of the building’s living and bedrooms space over the period of one year. A second functional unit, ‘per dwelling is also chosen as the most favourable to policy making, especially as it will be useful in prioritizing residential upgrade projects within any available limited funding.
Environmental impact categories
In this study, global warming potential (GWP) and primary energy (PE) as environmental impact categories are assessed for the different archetype representative dwellings. They are chosen on the basis of literature; international agreements;
feasibility; the most significant impact category attributed to the building sector; and regional and national policies, and in particular as most environmental indicators published by Irish government agencies focus on greenhouse gas emissions and primary energy. In addition, primary energy is regarded as comprehensible measure for typifying the life cycle of a building system, and in particular as it represents a significant indicator for a variety of environmental impacts.
Characterisation
As a detailed discussion of characterisation has been previously carried out in Chapter two, in this study, the characterisation of the environmental impact, global warming, an operational Guide to the ISO Standards 2001 (CML2001) also referred to as the
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classical impact characterisation method of CML (Centre for Environmental Science, Leiden University) is used. Once all relevant life cycle inventories are generated and used as inputs into GaBi software tools, the quantitative estimation of life cycle impact indicators or the evaluation of the impact assessment results are automatically generated.
Building system
The building system represents the total system of processes required for the building (Blengini, 2009), together with its linked material and energy flows. In this study, the building system comprised unit processes, each of which indicates one or several activities, such as extraction/mining of raw materials, refinement, processing and manufacturing of materials, operation, retrofit, maintenance, and disassembly of the building including all associated transportation. Across the continuum of processes, data are recorded on the inputs of natural resources, the emissions, waste flows, and other environmental exchanges. These environmental exchanges to and from the building system are directly linked to one of the building flows of the unit process. Furthermore, all unit processes are linked through intermediate building flows. Figure 4.8 illustrates study house system boundary (life cycle diagram). While the main oval solid shaped represents house system boundary, dashed dot arrows represent relationship between several life cycle phases, such as waste management of materials of disassembly. It should be noted that these links are outside the scope of this study but represents potential negative and positive values of recycling. Similarly, Figure 4.9 represents an example of a unit process within a building system.
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windows , doors, insulation, concrete, screed, appliances, fans,
Figure 4.8: Study house system boundary
Figure 4.9: Example of a unit process within a building system
Life Cycle Inventory (LCI)
Life cycle inventory analysis (LCI) is the second stage of an LCA (ISO 14040:2006).
Life cycle analysis is composed of inputs and outputs in the form of environmental exchanges to and from the building with regard to the building being studied. It involves data collection and calculation procedures to quantify relevant inputs and outputs of a building product system.
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A generic parameterized building model was developed in the software GaBi 4.4 (LBP
& PE, 2007) in order to simplify the handling of the extended quantity of data and maintain consistency during the assessment of all representative archetype houses. The use of generic models in GaBi 4.4 software tool permits the efficient adaptation of the model to contrasting representative archetype houses by parameterising key variables, such as mass or energy fluxes (Nemry et al, 2010). In this respect and based on mass, all representative archetype houses to be evaluated shared a common arrangement within the GaBi 4.4 scenario parameter explorer. Further details are provided in Section 2.4.1 of Chapter 2 on the application of GaBi software tool.
Service life of products and of complete buildings
Like complete buildings, service life assumptions for building materials are required in order to evaluate the energy and environmental impacts of the buildings. The service lives of manufactured materials, products and equipment have been assumed based on manufacturers’ information, literature and examples from previous renovation projects- many of such examples are in Energy Saving Trust (EST, 2007, 2010). Table 4.1 illustrates life expectancy of the construction materials and components used in the study. Similarly, Table 4.2 illustrates house material component replacement rates for maximum service life. The data have been considered appropriate as most of them are based on past practical projects and previous studies on upgrade projects.
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Table 4.1: The life expectancy of construction materials and components
Material and component Life
expectancy in years
Reference Comment
1 Windows and doors 40+ EST, (2005)
2 Roof coverings 60+ EST, (2005) Contingent upon installation this element is expected to last the life of the building
6 Brown goods 3 Assumption is based on experience
and products brochure 7 Insulation, joist, internal
walls
50 SABO, (1992) Internal wall was assumed for plasterboard
10 Water pipes and electric wires
50 SABO, (1992) Element is expected to last the life of the building
11 Manufactured fireplace 50 Medgar L. et al., (2008)
Element is expected to last the life of the building
12 Boiler 16 SABO, (1992)
13 Wood-fuelled heating appliance
20 EST, (2007)
14 Photovoltaic panel 30 Manufacturers’ brochure
15 Solar thermal system 25 EST, (2005), replacements is determined as follows (Adalberth, 1997):
material 1
Where, -1 in the formula represents first installation at construction of the building.
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Table 4.2: House material component replacement rates for maximum service life
Replacement
4 Conventional/condensing boiler 2*
5 PV system 1
6 Solar plate 1 (n/a)
7 Water pump 2
8 GSHP and ashp compressors 1
9 Solar thermal system 1
Parenthesis indicates material/product is not part of the package for the no-intervention option; *indicates material/product is not part of the package for the passive house standard option.
Several sources of data
In this section several data sources used in performing the analysis are discussed. It involves compilation of both process analysis and input-output analysis data. Table 4.3 illustrates the combination of several data sources used in this study. Similarly, Table 4.4 illustrates Sources of additional data.
Process analysis data
Overall, process analysis data incorporates data on the physical flows of all processes that are related to the production, consumption and disassembly phases of the house in question. The Energy Performance Survey of Irish Housing (EPSIH) provides the life cycle inventories of construction materials and energy as well as of transportation processes. Similarly, Background datasets are European averages as provided within the GaBi 4.4 software tool including other databases such the European Life Cycle Database, and Plastics Europe.
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Table 4.3: Combination of different sources of data according to life cycle phases Sources of data
life cycle phase
Unit process Process analysis Input-output analysis Maintenance Production of
• Cost of transportation from a previous study
Other process analysis data were taken from a previous study (Acquaye, 2010). These include percentage shares of national arising embodied CO2-eq intensity and international arising embodied CO2-eq intensity of Irish construction, representing 12%
and 84%, respectively. The author derived these intensities by applying national emission factors to convert embodied energy intensities of Irish construction to embodied CO2-eq intensities. The source of energy for crane lifting is further discussed in the section next sections under life cycle inventories.
143 Table 4.4: Sources of additional data
Building product Reference
1 Copper Deutsches Kupferinstitut, Life Cycle Centre
2 Steel http://www.worldsteel.org
3 Radiators http://www.inspiredheating.co.uk/acatalog/Heatrae_Meg aflo_Direct_Unvented_Hot_Water_Cylinder.html 4 Boiler-Potterton Promax FSB 30
HE
http://www.energysavingtrust.org.uk/Compare-and-buy- products/Heating/Gas-boilers/Potterton-Promax-FSB-30-HE
5 Solar hot water system www.csgsolar.com 6 Air Source Heat Pump www.altherma.co.uk 7 Biomass boilers, burners and
stoves
http://www.treco.co.uk/tatano/
8 DHW pump Combi-Cat Model CC-1
9 DHW cylinder Ariston. www.centralheating.co.uk 10 VENTOS 50 DC Stand-alone
comfort ventilation (MVHR) unit
www.paul-lueftung.net
11 Photovoltaic Cells 1) http://www.solartubecompany.co.uk/photovoltaic-cells/
2) Solar Module:
http://www.gzrichsum.com/webs/solar-module-01.htm
12 DHW Solar cylinder Kingspan cylinder - Technical specifications Indirect solar Applications using Tribune HE Solar Units
Data gaps: The international impacts induced by the provision of workman’s clothing, transportation vehicle and insurance were not calculated due to a lack of data. Such omitted inputs include costs, and energy and emissions intensities of the processes involved in their provision. Even in cases when these inputs are known, it is likely to become intractable to quantify the proportion of those that are attributable to this study as some of the materials and products are expected to be reused on several other sites that are not related to the building in question. However, these data gaps are not expected to lead to any significant error in the analysis.
144 Energy and LCA tools used in the study
The annual house operational energy use for heating, lighting, ventilation and appliances was modelled using EDEM/HEM energy modelling tool (See Section 2.4.1 of Chapter 2 – review of literature). Similarly, the impacts attributable to the representative archetypes’ across life cycle phases (including the outputs of EDEM/HEM for the operation of the building) were evaluated using the GaBi 4.4 LCA tool (See also Section 2.4.1 of Chapter 2 – review of literature).
Life cycle inventories (process analysis)
Using the detailed technical descriptions for each archetype, and other life cycle inventory data from the EPSIH, life cycle inventories for the refurbishment work were generated. Residual building service lives and the life expectancy of the products/materials were also used in this process. The rate of replacement yields the number of replacements of products (e.g. replacing PV system every 30 years) and number of upgrade actions (e.g. internal and external redecorations every 7 and 10 years, respectively) for each construction detail over the residual life of the building.
However, for the purposes of generating mass of materials quantities to be transported to recyclers (as pre-use phase of the building is outside the scope of this study) at disassembly, a list of materials quantities was generated for archetype one for the BaseCase scenario. This resulted in the total mass of materials for transportation at disassembly. Since envelope construction (i.e. concrete roof, solid floor and masonry wall) is similar for all archetypes and represents the bulk of the mass for transportation, the mass of materials for transportation for each of the remaining archetypes was then calculated based on the mass per m2 derived from archetype one. The procedure was also repeated for all retrofit options. Tables of mass of house materials list for archetype
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1 across all house options are presented in Appendix 3. The weights (kg) of these materials are then weighted to obtain those of the remaining archetypes.
On the basis of the study house system boundary, four life cycle phases were considered. These include operation, retrofitting, maintenance and disassembly phases.
The construction phase burdens were not considered as the emissions from the phase are considered ‘sunk’ emissions as these have already been incurred and cannot be recovered. The impacts induced by fixing of retrofitting materials and products during renovation and maintenance was also excluded from this present section but accounted for in the section under input-output analysis as these represent processes for which only I-O data are available.
The life cycle inventories for each life cycle phase considered are described below.
a) Maintenance phase
On the basis of the study house system boundary, the maintenance phase in the building’s life cycle encompasses all activities required to produce all materials, products and components required for replacement at the end of their service lives. A complete list of maintenance materials is included in the bill of materials quantities prepared for this study.
Material production for the maintenance phase includes burdens (embodied primary energy and related emissions) from material extraction, refinement, processing and manufacture of materials, products and components including all associated transportation to site (see Table 4.7 above).
146 b) Retrofit phase
The retrofit phase in the building’s life cycle encompasses all activities required in the application of energy saving components to the building. A complete list of materials due to retrofit of the building is included in the bill of materials quantities prepared for this study.
Material production for retrofit phase includes burdens from material extraction, refinement, processing and manufacture of materials, products and components including all associated transportation to site.
c) Operation phase
Operation phase of the building includes energy and burdens from households’ use of heat energy and electricity for space and water heating, lighting and appliances. It also includes energy and burdens from transportation of purchased thermal heat (e.g. oil) from suppliers to the building site. The impacts of the operation phase have been calculated as a function of fuel use. The energy requirements during the operational phase were calculated using the HEM energy modelling software tool. It calculates annual energy requirements for space heating, water heating, ventilation and electricity.
Factors taken into consideration include: fabric inputs (U-values of the construction details, thermal bridges, air leakage, window size, exposure, shape, floor area, capacity, and capacity position); system inputs(system fuel, heating system type, hot water system type, controls, lights, ventilation/cooling and renewables); and demand-related inputs (climate, heating demand, hot water demand, appliances and grid CO2 intensity).
147 d) Demolition of the building
Demolition of the building includes energy and burdens from the conversion of energy used for removing recyclable materials and their transportation as well as the actual demolition of the buildings. This energy is mainly energy use due to crane lifting, excavation, the removal of ground floor slabs, and leveling the site. The energy used for these processes was calculated using data collected by the Danish Research Institute (Andersen et al, 1993). The authors found this energy to be 2kWh/m2 for crane lifting;
3kWh/m3 for excavation and removal of ground floor concrete slab; and 3kWh/ton for smoothing of soil, respectively. The phase also includes burdens from the production and consumption of fuels used for transporting all waste.
Transportation assumptions
This present study assumes there is a recycler nearby the building at approximately 50km. It should be noted that the supplier of the new products during maintenance are expected to transport all waste materials to a recyclers where they will be sorted and sent for reuse or recycling or energy recovery or landfill. The transport dataset from GaBi 4.4 already accounts for the transportation of fuels from the point of extraction/mining to the manufacturing centre of the required finished products.
However, transportation burdens from the mainstream and downstream sectors are also based on the transportation dataset from GaBi 4.4 and are modelled based on an assumed distance of 50 km from suppliers to the building site, and of waste from building site to recycler.
Other omitted processes
Inventories of some processes and features were excluded from the house system boundary due to insignificant application. These include white and brown goods,
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especially since these can be separated from the building and are not fixed. This study was therefore limited to the building elements, heating system, and electrical system.
Energy sources
In the calculation of environmental impacts, it is assumed that the energy supply system will be constant during the entire lifetime of the building. The current Irish electricity grid mix has been used to evaluate the environmental impact induced by electricity production for all buildings. Similarly, environmental impacts from heat production were calculated using Irish fuel parameters for natural gas and oil and based on GaBi energy and emissions intensities.