Net climatic impact of solid foam insulation produced with halocarbon and non-halocarbon blowing agents

The net climatic effect of increasing the amount of insulation in buildings through the use of halocarbon-blown foam insulation involves three factors: the greenhouse gas emissions associated with the energy used to make the insulation; the climatic impact of leakage of the halocarbon blowing agent from the insulation during its manufacture, use, and at the time of disposal; and the reduction in heating and/or cooling energy use and associated greenhouse gas emissions. Recent studies and assessments leave the impression that the use of halocarbon-blown foam insulation has a strong net positive impact on climate, with the reduction in heating-related emissions being 20-100 times greater than the CO2-equivalent halocarbon emissions. This result applies only to the overall impact of rather modest levels of insulation applied to a pre-existing roof or wall with negligible thermal resistance. It is appropriate to consider the time required for heating-related emission savings to offset halocarbon and manufacturing emissions for the addition of successive increments of insulation-the marginal payback time. For typical blowing agent leakage rates and for insulation levels found in high-performance houses, marginal payback times can be in excess of 100 years using halocarbon blowing agents, but are only 10-50 years using non-halocarbon blowing agents. With a fixed thickness of insulation, the difference in heating energy savings using insulation with different blowing agents is generally only a few per cent, in spite of differences in thermal conductivity of up to 66%. The net savings in CO2-equivalent emissions is larger using non-halocarbon blowing agents, with the relative benefit of using non-halocarbon blowing agents greater the greater the thermal resistance of the envelope element prior to adding foam insulation. (c) 2006 Elsevier Ltd. All rights reserved.