An estimate of the technological and economic potential of energy efficiency measures was recently prepared for the IPCC (Acosta Moreno et al., 1996).¹¹ This analysis provides an estimate of energy efficiency potential for buildings on a global basis. Using the B2 Message marker scenario (Nakicenovic et al., 2000) as the base case,¹² the analysis indicates an overall technical and economic potential for reducing energy-related CO₂ emissions in the buildings sector of 715MtC/yr in 2010 for a base case with carbon emissions of 2,600MtC/yr (27%), of 950MtC/yr in 2020 for a base case with carbon emissions of 3,000MtC/yr (31%), and of 2,025MtC/yr in 2050 for a base case with carbon emissions of 3,900MtC/yr (52%) (see Table 3.5).¹³ It is important to note that the availability of technologies to achieve such savings cost-effectively depends critically on significant R&D efforts.

Table 3.5: Technical and economic potential for reducing energy-related carbon dioxide emissions from the buildings sector (Acosta Moreno et al., 1996).
	Projected emissions reductions (MtC)				Share of projected total emissions
	2010	2020	2050		2010	2020	2050
Developed Countries + EIT Region
Residential	325	420	660		30%	35%	54%
Commercial	185	245	450		32%	38%	68%
Total	510	665	1110		31%	36%	59%
Developing Countries
Residential	125	170	515		20%	21%	39%
Commercial	80	115	400		24%	26%	57%
Total	205	285	915		21%	23%	45%
World	715	950	2025		27%	31%	52%
Note: Projected total emissions based on B2 Message marker scenario (standardized) (Nakicenovic et al., 2000).

Estimates of the ranges of costs of carbon reductions are based on a synthesis of recent studies of costs (Brown et al., 1998); these estimates are similar to those provided in an International Energy Agency Workshop on Technologies to Reduce Greenhouse Gas Emissions (IEA, 1999a). The qualitative rankings for the reductions in carbon emissions follow the results of the IPCC Technical Paper (Acosta Moreno et al., 1996). In general, it is assumed that costs are initially somewhat higher in developing countries because of the reduced availability of advanced technology and the lack of a sufficient delivery infrastructure. However, depending upon conditions in the country or region, these high costs could be offset by the fact that there are many more low-cost opportunities to improve energy efficiency in most developing countries.

These studies show that with aggressive implementation of energy-efficient technologies and measures, CO₂ emissions from residential buildings in 2010 can be reduced by 325MtC in developed countries and the EIT region at costs ranging from –US$250 to –US$150/tC saved and by 125MtC in developing countries at costs of –US$200 to US$50/tC saved. Similarly, CO₂ emissions from commercial buildings in 2010 can be reduced by 185MtC in developed countries and the EIT region at costs ranging from –US$400 to –US$250/tC saved and by 80MtC in developing countries at costs ranging from -US$400 to US$0/tC saved.

Energy demand in buildings worldwide grew almost 3% per year from 1971 to 1990, dropping slightly after that as a consequence of the significant decrease in energy use in the EIT region. Growth in buildings energy use in all other regions of the world continued at an average rate of 2.5% per year since 1990. This growth has been driven by a wide variety of social, economic, and demographic factors. Although there is no assurance that these factors will continue as they have in the past, there is also no apparent means to modify most of the fundamental drivers of energy demand in residential and commercial buildings. However, there is considerable promise for improving the energy efficiency of appliances and equipment used in buildings, improving building thermal integrity, reducing the carbon intensity of fuels used in buildings, reducing the emissions of HFCs, and limiting the use of HFCs to those areas where appropriate. There are many cost-effective technologies and measures that have the potential to significantly reduce the growth in GHG emissions from buildings in both developing and developed countries by improving the energy performance of whole buildings, as well as reducing GHG emissions from appliances and equipment within the buildings.

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