Direct-gain mass

Passive solar buildings contain thermal storage materials to perform comfortably and efficiently. The requirement for thermal storage is especially demanding in direct-gain buildings in which the storage and release of heat occur at exposed room surfaces. The temperature changes that drive energy into and out of storage are roughly those experienced by the occupants. The storage materials need, therefore, to perform effectively within the limits of comfortable temperature changes. Furthermore, the thermal storage materials are the very materials that comprise the interior room surfaces. The materials are likely, therefore, to be standard interior finish materials. Specialized products might work better, but building professionals or owners are likely to reject them if they look or handle differently, or if they cost more, than standard materials. There are two approaches to improve the situation, both of which have stimulated active areas of research. One approach is to develop new, highly effective thermal storage materials that could become standard interior finish materials. The second, and conventional, approach is the intelligent use of standard building materials for thermal storage. This approach entails the use of existing, heavy materials such as concrete and brick, but requires detailed knowledge of how thermal storage works in buildingsmore » and how to estimate the performance of a given configuration of materials.« less