ABSTRACT
In passive solar architecture, a wall is more than a wall, it may be part of an insulating envelope, a space divider, a solar collector, thermal mass, a light reflector or a director of breezes. A passive building must first be an energy conserving building. The above nominal insulation value is typically much higher than the actual value of the wall because of conduction through framing and less than perfect installation. Infiltration losses can be just as great as conductive losses and may easily account for half of the winter heat loss in a well insulated, but poorly weatherized building. Recent improvements in insulation and glazing techniques have made air infiltration the prime contributor to winter heat loss. Non-toxic materials, finishes and furnishings are preferable. As modern architecture matured most buildings became smooth seamless envelopes, sealed to allow thermal conditioning and lighting by mechanical and electrical equipment.
