Conclusions from ten years of Canadian attic research.

Canada Mortgage and Housing Corporation (CMHC) conducted a series of attic research projects from 1988to1997. Initially, there were few field test data to substantiate how attics dealt with air and moisture transfer. The CMHC research developed a test protocol for attic airtightness and air change testing and then proceeded to field testing of a variety of attics in different climatic areas. An attic model, ATTIX, was referenced against test hut data and used to simulate attic performance across Canada. The latest research project compared the performance of nominally identical attics, one of each pair with full, code-required venting and one with all intentional holes sealed. Results show that ventilation plays a relatively small part in the control of attic moisture and temperature but, conversely, rarely provokes major moisture problems. This suggests that there is no significant advantage in changing current Canadian attic code requirements, except perhaps by allowing more flexibility in venting design.