|Housewraps are products meant to be installed
under the siding of a building. They perform
three desirable functions. The first is to
provide a membrane that allows water vapor
to escape from framing lumber and insulation,
so that it does not cause damage to the structure.
Housewraps also create a weather barrier
beneath the siding, preventing rain driven
by the wind or other moisture from reaching
the sheathing. The third function is to serve
as an air barrier that helps to reduce heating
and cooling expenses.
If you are thinking installing a housewrap
on your structure, consider the following:
- Felt paper has been used for many decades
as a housewrap, but newer technology has
resulted in plastic based products. It is
important to choose the housewrap based on
the exterior siding being used. Vinyl, wood,
brick and stucco all have specific requirements
and need different types of housewraps.
- Permeance ratings (perms) are a measure of
the housewrap’s ability to
vapor. The higher the perm
number, the more
permeable the material is.
codes require a rating of at
least 5.0. Most
available housewraps have ratings
6.7 and 59.0.
- Housewraps should be installed from the bottom
up, with each layer overlapping
the one below
it. The seams should be sealed
made especially for the specific
housewrap. Any cuts in the
be carefully lapped and taped.
Any housewrap product is only as good as
the quality of its installation. Badly installed
housewraps can cause serious problems in
the future, so make sure you follow all directions
closely or hire a competent installer.