The thermal performance of buildings can be significantly improved by the application of PCM. Used in a building’s envelope, the PCM controls the heat flux into and out of the building. Research has shown that the roof of the building provides the most efficient location for the PCM. In order to integrate the PCM into a roof structure, composite building materials have been developed consisting of a polymer with incorporated PCM applied as a coating to a textile carrier material. These composite materials can replace the underlay or the water vapor barrier currently used in roof structures, and can supplement the effects of the insulation during periods of peak demand. On the one hand, the application of these composite materials in place of the underlay in the roof of a building significantly reduces the temperature in the interior on hot days. Therefore, a substantial decrease in the air-conditioning demands of a building is obtained. On the other hand, when another layer of PCM roofing material is substituted for the water vapour barrier, its heat retention properties will reduce the annual heating demands of the building.
For other applications of PCM in building materials, please see architectural membranes.