In the past, builders rarely thought about ventilation for
the houses they built. Standard practice resulted in
houses that kept out big, uncomfortable drafts, but that still
allowed in plenty of fresh air. Today, builders are routinely
producing houses that are much tighter — often without
even realizing it (see illustration, next page). It is clear
from recent research that builders can no longer rely on air
leakage alone to provide enough ventilation.
Evidence of lower ventilation rates has been seen in
numerous studies done across the U.S. and Canada. A
study of 64 randomly selected new houses built in 1984
in Minnesota showed that 80% failed to meet recognized
minimum ventilation