I was told 2" is good, but if you wanted a vapor barrier it had to be 3" minimum. The additional cost was more than I could afford, not to mention, I skipped the house wrap once I knew I was going with spray foam......and they said with the open cell, I could replace a panel if I needed to......but with closed cell, its not coming off!!
I don't think you can go wrong either way......nothing seals like foam, open or closed. Closed has its advantages, but at a cost. If its not in your budget, I think open cell is the next best option.
The thickness has to do with condensation .. .not VB with closed.
Open needs 5" for full air sealing --- since air sealing is important in any climate -- you need 5" to get the job done.
At 2" in a cold climate the closed may still be under the dew point on a cold day ... if this is the case water can condense in the wall.
Non of the above has anything to due with the house wrap .... house wrap of some nature needs to be done to protect the sheeting from moisture from the outside.
Simple quality felt paper works great .... unfortunately the stuff from the bog box stores is not traditional felt and is junk. Tyvek was introduced to also act as a wind barrier ... this was especially needed in old houses with board sheathing. House wrap is often not done correctly ... this is why many builders are moving to Zip ... Zip has it's own issues IMO
Closed cell is a superior product IMO ---- the open cell guys try everything to make the open seem like it has some advantage. It's cheaper ... that's the advantage In a warm climate with new construction the case for going open and saving some money can be made when doing a huge building ...like a big garage.
When rehabbing w/ 2x4 walls or a new house .... the savings IMO do not add up
in a cold climate
