I am currently in the process of renovating a back room that would get
very cold in the winter (we live in Ontario, Canada). After gutting
the room I noticed that there was no house wrap under the siding. My
question is, can I apply house wrap from the inside, between the studs
before I insulate and apply a vapor barrier? Does the house wrap have
to sit on the exterior of the house between the siding and the wall or
can I go ahead and tack it up inside?
House wrap does two things. It provides a water repellent barrier and a
air resistant barrier, but not a vapor barrier.
Adding it inside the wall will not help with the water repellent barrier
at all. In the old days tar paper was the usual choice. You may already
have that need covered.
The air infiltration barrier can be anywhere. I would think it would
make it easier to make it part of the vapor barrier you are going to be
using anyway. Just seal up the breaks, like outlet boxes tighter than
usual. The reason they use the house wrap is because there are usually
fewer breaks for things like outlets and it can work as the water repellent
at the same time.
The purpose of house wrap is too slow air movement, specifically wind
loss of heat. To do that it needs to be continous and without breaks
(lots of house wraps are essentially useless because during
construction it is torn and damaged and never repaired correctly.
So the question is, "How are you going to seal it air tight from stud
to stud and floor plate to top plate?" You probably can't, so it
will probably be useless to some fraction of 100 percent. If you have
lots of time and want to work very precisely, go for it. Otherwise,
forget the house wrap.
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