I have been a General Contrator for 35 years. We just built a new home for a customer and we have frost on the drywall. The home is fully insulated. Our company, my insulator, my HVAC people cannot figure out the problem. Any idea's on the cause and/or fix.
Tom

To get frost, you need two things:
a) a really cold wall; and
b) extra humidity inside the house

Humidity can come from a number of sources: paint or plaster drying, cooking, showers, humidifiers. The frost would go away once you remove the source of humidity.

However that will still leave you with a cold wall - which is the real problem here. There is just no denying the physics. Somehow the surface of the drywall is getting down below freezing. That's difficult to do. Our first house was not insulated at all, and on days where is was -40, we'd still not have frost.

Is the frost over the whole wall, or just one small spot? It must be a combination of lack of insulation or some breeze from somewhere.

Did the homeowner have anything stored up againist that wall like a box or pile of blankets? I have seen frost form when the wall became insulated from the room heat by a large object. It could be that or its time to drill some test holes to see how thick that insulation really is.

You will have to remove the drywall and you may want to spray foam the wall this might help

Do not do any repair until we discuss this further. Try to answer my question, above all do not remove the drywall yet.

My stab at this was a vapor barrier was forgotten or put on the wrong side of the wall cavity. Or the insul contractor somehow forgot to insul a stud cavity.
Can you more specific as to where the wall is located and is the frost at the bottom of the wall? The whole wall top to bottom? In the inside corners of the room outer walls?
At this point looking at the wall won't fix a thing. I would check for cold air around the outlets on that wall and other boxes that are in that wall. Then I would pop the baseboard and get above the bottom plate and reach inside the wall to feel for a vapor barrier and check all wall cavities on that wall and that guessing is over. Did your men use sill plate insulation when it was built? What the whole details in the actual wall construction since you are a builder that should be . Is there a house wrap under the siding at all and did that cover the whole outside band of the floor joist ?
So if these questions could be answered that would help a lot.
Personally as one builder to another I would bite the bullet and pop the baseboard on that wall and then know for sure what's actually behind there. Also that will show your customers that you don't mess around and are physically attacking the problem. I just know as a builder if you jerk this around it will create a friction from the home owner and they will eagle Eye ALL the other work and maybe start to nit pick on much minor things of any finish work done. So friend This is what we call on our job after all the thinking is done "When in doubt Tear it out" and solve many questions in the variables

Signed 21 Boat

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