O BJETIVOS E STRATÉGICOS

In the recent Fifth Assessment Report of the Intergovernmental Panel on Climate Change it was noted that 117 Exajoules (EJ) or 32% of global final energy consumption and 19% of energy-related CO2 emissions were generated from buildings. This equated

to 51% of global electricity consumption being associated with buildings (IPCC, 2014). The direct emissions of CO2 from the building sector (excluding the emissions from

electricity use) has been estimated globally at about 3 GtCO2, 0.4 GtCO2-eq CH4, 0.1

GtCO2-eq N2O and 1.5 GtCO2-eq halocarbons (including CFCs and HCFCs) (Levine et al.,

2007). The greatest use of energy in buildings is during their in-use phase, with Levine et al. (2007) estimating this to be around 80% of total life cycle energy whilst the construction operation itself consumes 15-20% of energy. As an EIO-LCA of the US construction sector noted, less than 40% of the total energy footprint could be attributed to direct or on-site construction activities. Furthermore, when assessing CO2

37 reporting (WRI, WBCSD, 2004), they identified that key scope 3 supply chain emissions were generated by electric power generation, transmission, and distribution, cement manufacturing, truck transportation, petroleum refineries, iron and steel mills and ferro alloy manufacturing, and oil and gas extraction (Kucukvar, Tatari, 2013).

Identifying the emissions from the different life stages for UK built assets continues to be difficult and highly specific to building type, use and life span selected. A report by the UK Government (BIS, 2010a) suggested that 80% of emissions were from the in-use phase, 15% embodied in the materials used and only 1% derived from the construction of the building. These figures were based on ONS Environmental Accounts, National Inventory or CRF, DECC data and industry sources. Acquaye and Duffy (2010) in their review of the Irish construction sector identified just 1% of CO2 emissions were

generated during construction, and of these sub sector: structural works emitted the highest proportion of CO2. A further UK publication by the UK Innovation and Growth

Team expanded this data and estimated 0.4% of CO2 emissions were derived from the

design phase, 15.1% from manufacturing, 0.9% transport of construction material, just 0.9% construction whilst 82.3% was from the operational or in-use phase, and only 0.4% are related to demolition (BIS, 2010b). A report by The Green Construction Board in 2013 produced similar findings with 18% CO2 attributable to capital or embodied carbon of

direct process emissions and indirect emissions from the manufacture and production of UK and imported construction materials and products, emissions from the transport of materials, emissions associated with professional services in support of construction, and all C&D work on site (Ove Arup and Partners Ltd, The Climate Centre & WRAP, 2013).

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Figure 5: The percentage of carbon in UK built environment by lifecycle stage, 2010 (Diagram, to scale, from data provided by Green Construction Board ‘Routemap’, (Ove Arup and Partners Ltd, The Climate Centre & WRAP, 2013))

39 The analysis also identified that domestic and industrial operational activity generated 79.6% of CO2 and the balance of 21.4% was derived from operational infrastructure. The

latter included emissions from water/wastewater, outdoor lighting and construction and demolition (C&D) waste treatment but excluded emissions from use of infrastructure by vehicles. The baseline was developed from UK emissions data 1990- 2010 (Arup, The Climate Centre and WRAP 2013) and is represented visually in Figure 5.

Whilst information at a sector level provides a general indication of emissions, industry is increasingly looking to understand this by building type. Studies using Life Cycle Analysis (LCA) and hybrid EIO-LCA are available but comparisons prove complex as there is not only variation in where boundaries are set, or the type of emissions measured, e.g. energy or CO2, the quality of the data sets used, but also in the length of life

attributed to buildings and the effect of country/site conditions. In his review of embodied carbon research, Ibn Mohammed noted that building life span ranged from 25-100 years, and that results showed significant variation between countries (Ibn- Mohammed et al., 2013). The difficulties this variation presents can be seen for example even where one type of building, an office block, is selected. Based on academic research a large office block in Thailand demonstrated 19% of energy was embodied (Kofoworola, Gheewala, 2009), another office block in Canada identified 14% (Cole, Kernan, 1996), whilst a smaller office unit in the UK had 25% embodied carbon (Eaton, Amato, 1998). More recent work by the Royal Institute of Chartered Surveyors (RICS) (Figure 6), using building regulation requirements, suggests that embodied carbon will continue to play an increasingly significant role in the whole life of the building. Whilst this may vary considerably by building type, they identify at least 50% of the carbon associated with buildings over a 30 year lifespan, is embodied (RICS, 2014).

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Figure 6: Relative Impact of the consequent life cycle stages on the overall carbon footprint for different types of buildings, calculated over 30 years (the energy results have been based on the building regulations) (RICS, 2014).

Further granularity of emissions has been mapped by Aitkins, a global design, engineering and project management consultancy, by considering over 50 different building types. This has provided a benchmark which suggests the majority of major buildings constructed have between 500-1500 kg CO2e/m2 (RICS, 2014). This work,

although associated with a high degree of uncertainty, has been derived from their commercial emissions database. Assumptions relating to different phases continue to be challenged as exemplified in a recent report by Innovate UK which notes that in a sample of 100 UK buildings CO2 emissions were underestimated during the in-use phase

by a magnitude of 3.6 (Innovate UK, 2015, Palmer, Armitage, 2014).

Due to climate change concerns most literature relating to the lifecycle impacts of buildings tends to focus on the main greenhouse gas emission: carbon dioxide. However, other embodied gases have also been assessed using an LCA approach, including studies which consider their impact on air quality. Of the three emissions most associated with air quality issues, PM10, SO2 and NOx, the latter two were primarily emitted at the

operational phase of building (approximately 70-80%), whilst around 80% of PM10 was

embodied in the built asset. However, the results for embodied PM10 may be lower as

emissions during use phase were not included in the research (Bilec, Ries & Matthews, 2010). It was estimated that approximately 5kg of PM10 was emitted per m2 of building

41 accurate data and benchmarks and could support more effective targeting of air quality policies.