This paper reviews empirical data from evaluations of the influence of residential energy efficiency retrofits on indoor environmental quality conditions and self-reported thermal comfort and health. Data were extracted from 36 studies described in 44 papers plus two reports. Nearly all reviewed studies were performed in Europe or United States. Most studies evaluated retrofits of homes with low-income occupants. Indoor radon and formaldehyde concentrations tended to increase after retrofits that did not add whole-house mechanical ventilation.

Many recent major studies, including the IPCC’s Fourth Assessment Report, have attested that energy efficiency is humanity’s prime option to combat climate change in the short- to mid-term. The potential to avoid CO2 emissions cost-effectively has been reported to be significant through efficiency policies. However, the review of global research findings on the quantification of cost-effectiveness of opportunities through improved efficiency has highlighted that there is a major shortcoming in the vast majority of such calculations.

The building sector is not on track to lower total greenhouse gas emissions. Given that emissions from the sector represent nearly 40% of global energy-and process-related emissions, this represents a serious challenge to keeping global warming to 1.5oC. The Buildings sector must therefore decarbonize.To support this goal, this report focuses on policy drivers for decarbonisation, and the costs and benefits associated with their implementation.