IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group III: Mitigation of Climate Change

6.2 Trends in buildings sector emissions

In 2004, direct emissions from the buildings sector (excluding the emissions from electricity use) were about 3 GtCO2, 0.4 GtCO2-eq CH4, 0.1 GtCO2-eq N2O and 1.5 GtCO2-eq halocarbons (including CFCs and HCFCs). As mitigation in this sector includes a lot of measures aimed at electricity saving it is useful to compare the mitigation potential with carbon dioxide emissions, including those through the use of electricity. When including the emissions from electricity use, energy-related carbon dioxide emissions were 8.6 Gt/yr (Price et al., 2006), or almost a quarter of the global total carbon dioxide emissions as reported in Chapter 1. IEA estimates a somewhat higher fraction of carbon dioxide emissions due to buildings.

Figure 6.1 shows the estimated emissions of CO2 from energy use in buildings from two different perspectives. The bar at the left represents emissions of CO2 from all energy end-uses in buildings. The bar at the right represents only those emissions from direct combustion of fossil fuels. Because the electricity can be derived from fuels with lower carbon content than current fuels, CO2 emissions from electricity use in buildings can also be altered on the supply side.

Figure 6.1

Figure 6.1: Carbon dioxide emissions from energy, 2004

Sources: IEA, 2006e and Price et al. 2006.

Carbon dioxide emissions, including through the use of electricity in buildings, grew from 1971 to 2004 at an annual rate of 2%, – about equal to the overall growth rate of CO2 emissions from all uses of energy. CO2 emissions for commercial buildings grew at 2.5% per year and at 1.7% per year for residential buildings during this period. The largest regional increases in CO2 emissions (including through the use of electricity) for commercial buildings were from developing Asia (30%), North America (29%) and OECD Pacific (18%). The largest regional increase in CO2 emissions for residential buildings was from Developing Asia accounting for 42% and Middle East/North Africa with 19%.

During the past seven years since the IPCC Third Assessment Report (TAR, IPCC, 2001), CO2 emissions (including through the use of electricity) in residential buildings have increased at a much slower rate than the 30-year trend (annual rate of 0.1% versus trend of 1.4%) and emissions associated with commercial buildings have grown at a faster rate (3.0% per year in last five years) than the 30-year trend (2.2%) (Price et al., 2006).

Non-CO2 emissions (largely halocarbons, CFCs, and HCFCs, covered under the Montreal Protocol and HFCs) from cooling and refrigeration contribute more than 15% of the 8.6 GtCO2 emissions associated with buildings. About 1.5 GtCO2-eq of halocarbon (HFCs, CFCs and HCFCs) emissions, or 60% of the total halocarbon emissions was due to refrigerants and blowing agents for use in buildings (refrigerators, air conditioners and insulation) in 2002. Emissions due to these uses are projected to remain about constant until 2015 and decline if effective policies are pursued (IPCC/TEAP, 2005).