Heat transmission through building structures is a major contributor to cooling or heating loads in most instances. Traditional methods of evaluating these heat transmissions have shown to be tedious, inaccurate, very costly, or a combination of both. As a consequence, considerable effort has been made to develop dynamic thermal calculation methods that can meet accuracy requirements and be economically attractive.

The purpose of this paper is to present a more efficient way whereby equivalent thermophysical properties of completely hollow elements can be found in a straight forward manner. The properties so found belong to a fictitious homogeneous slab. The thermal behavior of this fictitious slab, is supposedly identical to that of the hollow element.