I just finished framing in a walk out basement and when the plumber showed up we removed the exsisting insulation from previously framed outside wall and noticed the inside of the sheathing coated in frost. The house is brand new, built by another contractor, the walls are 2 x6 with 1/2″ osb and vinyl siding. For some reason they used R-13 instead of R-19 and did a lousy job. The wall is about 16″ above the slab and sheathing is well above exterior ground level and the only current source of heat in basement is the furnace heating the rest of the house and keeping the basement somewhat warm. What is causing the frost? I have found what looks like a pisspoor siding job with several flashing problems, but the frost is everywhere and this is in Massachusettes where temps currently average about 15 degrees Any ideas welcome
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Warm moist air passing from the inside conditioned space, condensing and frosting on the sheeting?
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Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
Like Calvin said, there's nothing stopping the moisture from finding it's way to the outside cold sheathing. Once there, it condenses as frost.
Excellence is its own reward!
Then why is it that on the same day i was at a post &beam uninsulated room I built that is heated by a pellet stove and is almost all glass plus 4 skylights and I saw no frost
Those areas had solids exposed to the convection of warm air circulating so surfaces were warmer and the air more able to keep the moisture aloft in suspension but when the moisture drives through the insul;ation 'till it hits the cold surface of the sheathing, the insulation allows little air movement over that surface so it keeps building..
Excellence is its own reward!
Let me give you a test so you can prove it to your self.
take the insulation out of two bays and let the sheathing dry out. Now put it back in one bay and seal that bay off with plastic and duct tape. Just put the insulation back loosely in the other bay. Check and compare both after a week or so of cold weather. The frost will have returned to the bay with no vaporbar on the warm side.
You have to have moisture and cold surface to have condensation. You have a situation that allows both..
Excellence is its own reward!
So now any moisture that will get by a vapor barrier will remain inside the wall cavity until it eventually passes thru to the outside thru the sheathing, felt/typex, and siding.
Does a typical 70degree heat radiating from the inside of the house help pressure any moisture in the wall cavity to the outside, thus helping prevent an excessive moisture buildup in the cavity, as opposed to say an unheated or low heat source on the inside area?Half of good living is staying out of bad situations.
The other...proper application of risk.
When did you build the post and beam? Humidity levels are probably different. That and no air wash on the new one could be showing up as frost. Try the test and let us know.__________________________________________
Remodeling Contractor just outside the Glass City.
http://www.quittintime.com/
You didn't say, was there any kind of vapor barrier installed? It should have been on the inside (warm) side of the insulation. Was the frost already there as the insulation was removed?
Sheathing has Typar with vinyl and a 2x6 wall that had R-13 faced insulation just prpped in the bays. I TOOK OUT ALL THE INSULATION AND LET IT DRY FOR AWEEK THEN BLEACH WASHED IT DRIED IT AND SEALED IT WITH KILZ I THINK I AM ALL SET TO RE INSULATE WITH R-19 WITH KRAFT FACE AND FINISH BLUEBOARD