Effect of indoor mass on the time constant and thermal delay of buildings

A numerical procedure is presented for predicting the transient thermal behaviour of buildings and estimating time constant τ and thermal delay t_d. The proposed procedure is used to examine the effect of indoor mass on the above characteristics. The predicted effect of these is considerable; for example, the usual indoor mass in houses increases τ and t_d by up to 40 per cent, which is analysed to 25 per cent for interior partitions and 15 per cent for furnishings. Both τ and t_d are found to be linear functions of the mass of interior partitions M_p and furnishings M_f. These functions are given for typical buildings. A simple ‘time constant and thermal delay model’ is also proposed, which is in satisfactory agreement with the developed rigorous numerical solution. Components of τ and t_d are introduced, which express the contribution of any indoor construction element or piece of furniture to the ‘total’ time constant and thermal delay of buildings. The analysis in components, which are related to the corresponding ones of the ‘effective thermal capacitance’, provides useful information for the maximization of heat or cool storage in buildings. Copyright © 2000 John Wiley & Sons, Ltd.