The material of which a building (and especially its envelope) is constructed determine the relationship between the outdoor temperature and solar radiation conditions, and the indoor temperatures in non-air-conditioned buildings. In the case of building heated or cooled by a mechanical system the envelope’s materials determine the energy consumed by the system to maintain the indoor temperatures within the comfort limits, as specified by the thermostat setting.
Outdoor temperature and solar radiation follow diurnal cyclic patterns. The outdoor temperature has its minimum about sunrise, rises and reaches its maximum at an early afternoon hour, and then drops down. Quantitatively it is characterized by an average (the range between the maximum and the minimum) and a given swing around that average. Solar energy, striking and absorbed at the walls and roof surfaces during the daytime hours, causes an elevation of the indoor average temperature above the outdoor average.
While both the outdoor temperature and the solar radiation patterns are climatological factors beyond the control of the architect, there is a major difference between them for the aspect of the controllability of their effect on the indoor temperature and the energy consumption by mechanical thermal control systems. Using design details, it is much easier to control the effect of solar radiation than that of the outdoor temperature conditions.
Source : Racomplex.com