metal roof might have the advantage of avoiding dripping,
from the fact that it would interpose a barrier between
the moist air and the cold surface of the underside
of the roof....To accomplish this it will be necessary
to put the paper on very carefully, making tight joints
along the rafters.
—from Carpentry & Building, March 1887
(courtesy G.E. Hahns, USDA forest Products Lab)
by Bill Rose
Three separate studies, along with reports
in the press about them, have raised serious
questions about vapor barriers, sparking controversy
and confusion among people in the
A look at the facts, however, quickly puts
the matter to rest. Vapor barriers are just as
important as ever.