another house wrap question

[rookie]

I have been talking to a builder about the house my wife and I are preparing to build. He told me that he insulated the walls with blown in cellulose insulation and on the outside he wraps the house with a 1" tongue and groove foam board. He didn't think house wrap was neccessary with a brick veneer. I dont know anything about the foam board he spoke of but wondered if it had some kind of vapor barrier on the face of it. If it doesnt have a vapor barrier should I insist on a house wrap (assuming I hire him as the GC)?

[Cole]

Does he put this over the plywood, or is it just straight to the outside studs?

I know what he is talking about, and personally I think it is a waste of money.

[grumpydasmurf]

If it's brick I can't comment with 100% accuracy. Personally I won't install insulation without the house wrap, but I only install siding... not brick.

Also I have very little faith in the insulations that have the house wrap "built in" or actually adhered to one side of the insulation board. What I mean is, I don't think the vapor barrier is worth a damn when it's glued to the insulation.

[rookie]

the foam board goes over the sheathing on the house and he never said whether or not the stuff had a vapor barrier glued to the surface or not. It seems to me that the foam board would give extra wall thickness and extra R value my only concern was a vapor barrier. Tyvek is fairly cheap to buy and install isn't it? Even if the foam board has a vapor barrier should I go ahead and pay for the wrap?

[grumpydasmurf]

I install tyvek at the rate of $25 a square, which is $2.50 per square foot. I charge the same for 1/2" foam board.

if it were my house I would want the wrap... It's cheap insurance.

[rexmaster]

FYI

http://www.dow.com/styrofoam/na/res-us/index.htm

[JCA]

I believe brick exterior really, really, really, needs housewrap.

[danh]

Too many people are interchanging house wrap & vapor barrier, and I'm getting confused.

I thought housewrap was a high-perm material used as a dranage plane for rainwater that penetrates the exterior cladding in order to keep the exterior sheathing dry, with secondary uses as an air barrier system.

I thought vapor barriers were low-perm materials designed to prevent moisture transport via diffusion, installed on the warm side of the wall, with a secondary function to control air leakage when installed against batt insulations.

Exterior rigid board is installed in extreme cold climates to prevent heat loss through studs. It can be used to keep water off the OSB as well, but failure points for this dranage plane are at the joints. Cold climate details I've seen behind brick show rigid foam board & housewrap (eg building paper or tyvek).

I'd rather have a high perm rating on my exterior rigid. During the winter, when moisture is diffusing outward, the rigid is on the cold side of the wall - the perfect place to put a vapor barrier if you like condensation.

[Sweep]

These sites may help:

http://hem.dis.anl.gov/eehem/01/010902.html

http://www.buildingscience.com/whatsnew.htm