Experience with foam sheathing?
I’m working with a customer who wants to use exterior foam sheathing as recommended by Building Science Corporation. The builder is a bit nervous about some of the practical aspects, exposure time, ladder damage etc. and I was wondering if any of you folks had actually built houses using that system and if you would like to share any tips. I’m in the central NH area and if there is anybody with something in progress I’d like to check it out.
Thanks, Bill S.
Replies
Depending upon your neighborhood, don't think that you can "lock up" the house until the inside is drywalled. Easy pickin's to kick through the foam.
Also, Piffin has pointed out that foam sheathing on the exterior (potentially) puts a VB on the outside. Depending upon your climate, that may be a bad idea. I live in a heating climate (WI) and that makes sense to me.
If there is a gap between interior insulation and the sheathing and moisture makes it into the wall, it will condense on the inside of that sheathing surface.
However, if you are in a cooling climate, maybe that's the bee's knees?
Edited 5/27/2005 9:38 pm ET by Jim
My first house had foam sheathing. It didn't feel solid. If you closed a door even a little hard the whole house shook. It didn't seem to help a great deal with heat bills either, they were a little high per sq. ft.
I built one along with a Habitat for Humanity crew. 3 bedroom ranch. Our chapter was not impressed and decided we would not use it again even though Dow was willing to donate the sheathing foam ( we used donated foam for the first one ). Think about it -- we won't use it again even if it's free.
We used the 1/2" Dow foam sheathing ( which cost almost as much as 7/16" OSB ). The finished house did not feel solid at all.
By the time we braced all the corners with structural sheathing and surrounded all of the openings for windows and doors with OSB ( required by our local inspection authority) about 30% of the house was sheathed conventionally anyhow.
Foam has 2 major advantages - it is very light and it is very easy to cut - that's about all of the advantages I can see. Disadvantages - ever try to get a volunteer to consistantly hit studs with siding nails? How to attach Tyvek ( answer - long staples and hang the Tyvek just before you hang siding -- good luck on a Habitat project!) Make sure you keep the pile ballasted or you will be chasing foam sheets into the next county, makes an excellent sail.
Ladder damage was not an issue although I could see how it could be, especially on a two story model.
The R value of 1/2" foam is practically insignificant. It does form a moisture barrier which could cause problems as mentioned.
Jim
Never underestimate the value of a sharp pencil or good light.
Foam sheathing:
1) You will still have to use somethig to provide structural suppot in the house corners: OSB, diagional bracing, or whatever...
2) Will you end up with a double vapor barrier?
3) zero nail base... I hope the project doesn't specify any sidewall shingles...
4) well, it was popular in the 80s anyway...
5) BSC: has some good info/recomdations....
6) it is a great combination with vinyl siding - only thing is that break-ins can occur via theaves armed with a steak knife... :-)
7) well, it's cheap anyway,
So what is the benefit?... R2.5 max. Better to invest in some good insulatuon.