I am residing my 1978 house following some hail damage. I will be using vinyl siding. The house is sheathed with a layer of 1″ styrofoam, which is covered with roofing felt. I was planning on installing Dow-wrap before installing the new vinyl. My question is, is this necessary, a good idea, bad idea, or just belt and suspenders? I don’t mind the extra cost. My real cocern is will the house pass moisture to the outside effectively with the extra layer? I should mention that I live in Wisconsin, home of the Super Bowl Champs!
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If you have felt, I can't imagine any reason to put house wrap over the top of it.
If you live in Wisconsin I can't imagine NOT putting housewrap on. When we redid the siding on our 1976 house (southern MN) I installed Tyvek and carefully taped around windows and doors. Made a world of difference in the comfort of the house -- no longer does cold air blow through the electrical outlets in the winter time. The dining room (on the NW corner of the house) went from being uncomfortably cold in the winter to being our regular gathering spot year-round.
Good quality housewrap does not prevent moisture from passing through from the inside.
(However, since your house is sheathed in foam, it may be that if that were carefully taped it would be as effective as housewrap, provided there aren't too many holes in it.)
Normally, the foam would be taped on the outside and would make a GREAT air barrier... but it won't now that it has all those nailholes in it - as does the existing felt.
Since you are taking the siding off, you can take this opportunity and REALLY insulate the house on the exterior plane. Yes, it's a bigger project but it's not like energy is going to get cheaper. You could add another 2" of foam to the exterior, reset your windows to this new exterior plane, then really do the exterior sealing details right, with the correct flashing details and all seams foamed and taped.
How much will you spend on heating/cooling before you next have the exterior exposed again?