Solar Engineering of Thermal Processes, 4th Edition

Chapter 14

Building Heating: Passive and Hybrid Methods

The active systems described in the previous chapter are based on collectors and storage systems that are not necessarily integrated into a building structure. Passive systems can be distinguished from active systems on either of two bases. The first distinction lies in the degree to which the functions of collection and storage are integrated into the structure of the building; windows and the rooms behind them can serve as collectors, with storage provided as sensible heat of the building structure and contents as they change temperature. Second, many passive systems require no mechanical energy for moving fluids for their operation; fluids and energy move by virtue of the temperature gradients established by adsorption of radiation (and hence the term passive). (Mechanical energy may be used to move insulation for loss control or to move fluids to distribute absorbed energy from one part of a building to another.)

By nature, passive heating is intimately concerned with architecture, as the building itself functions as collector and storage unit and as the enclosure in which people live, work, and are protected from an often-harsh exterior environment. In this chapter we discuss in a largely qualitative way the factors that affect the thermal performance of a passive building (i.e., its ability to provide an acceptable level of human comfort). The engineering basis for thermal performance calculations is (as for active systems) ...