Thermal parameter components of building envelope

Abstract

A procedure is presented for analyzing the effective thermal capacitance, the time constant and the thermal delay of buildings into components corresponding to discrete sections of the envelope (i.e. the roof or a whole wall of a specified orientation), to envelope parts of different compositions (i.e. the brickwork and the concrete parts of the envelope), or even to the layers of the exterior multilayer walls. Correlations are also developed, which express the dynamic thermal parameters of buildings in terms of the thickness of exterior wall layers and the surface percentage of envelope parts with different compositions. The effective layer thickness is introduced, the increase of which causes negligible increase in the building thermal capacitance. The developed procedure is based on finite-difference solution of a rigorous set of coupled differential equations describing the dynamic thermal behaviour of buildings. The analysis made quantifies the thermal contribution of every element of the envelope and may improve its thermal behaviour if the related conclusions are taken into consideration in the design of buildings.