Conduction in the fabric of the building is treated dynamically using a method derived from the ASHRAE Response Factor technique. This efficient computational procedure calculates conductive heat flows at the surfaces of walls and other building elements as functions of the temperature histories at those surfaces. Constructions of any number of layers may be treated, where each layer may be composed of an opaque material (e.g. brick), a transparent material (e.g. glass) or a gas (e.g. air). Databases of materials and constructions are available.