A significant portion of the field of building science relates to the design and operation of the building enclosure. The building enclosure acts to define the space that it encloses. However, more than the building's outer dimension, the building enclosure is the barrier that separates the external climatic environment from the interior engineered climate. The properties of the building enclosure have a dramatic effect on the efficiency and functionality of the many systems that generate the interior climate.

The building enclosure is the building's skin, and like the skin of a living creature, building performance depends on the interrelationships between the building enclosure and the external environment.

Most notably, the building enclosure is subjected directly to the effects of the elements. In Canada, the seasonal climatic differences are significant. Additionally, the climatic differences vary dramatically from one side of the country to the other. The West Coast of Canada is characterized by a long rainy season with a short drying season, while the interior provinces are characterized by dramatic seasonal temperature fluctuations with limited yearly precipitation.

It is now recognized that the building enclosure must be designed specifically for the service considerations of each distinct climactic region. While this may seem logical, the "Condo Crisis" in the Lower Mainland of British Columbia represents some $2 billion dollars in damage specicially as a result of the enclosure design not being suited to the climate.

A better understanding of the building enclosure and the complex interrelationships with the external climatic environment will lead to improved efficiency and longevity of the many buildings that our society is dependent upon.