An improvement to frequency-domain regression method for calculating conduction transfer functions of building walls

An improvement is proposed for the frequency-domain regression (FDR) method to calculate CTF (conduction transfer function) coefficients of multilayer constructions. This improvement aims at providing complete CTF coefficients with a unique set of d values. In the improvement, the external and internal polynomial s-transfer functions of heat conduction of a wall are identified based on equivalent frequency response characteristics by constraining their denominators equal to that of the cross polynomial s-transfer function while this cross polynomial s-transfer function of this wall is identified using FDR method in advance. The complete CTF coefficients of this wall (i.e., external CTF values a, cross CTF values b, internal CTF values c and a unique set of heat flow rate history coefficients d) can be easily calculated from these identified polynomial s-transfer functions. Examples and comparisons show that this improvement of the frequency-domain regression method works well.