Approximating dynamic thermal behaviour of the building envelope

Assessing the building energy performance through the simplified assumptions of the steady-state conditions can prove restrictive. The estimation of heat transfer through the envelope is based on the U-value of the building construction, neglecting the thermal mass effect. Several approaches have, therefore, been developed to approximate the dynamic behaviour of buildings when performing a standard steady-state analysis. According to Barnaby (1982), these methods can be generally divided into those analysing an isolated building element and those considering the context of whole building. The first category introduces some correction values that affect the main parameters of the steady-state heat transmission calculation (i.e. the U-value of the envelope elements and the temperature difference between the indoor and outdoor environments). This chapter investigates a set of correction values that try to represent the dynamic thermal envelope performance in a simplified manner, applying some of them to a set of case-study wall types.