How do I install vapor barrier over the ceiling?  We took a heat gun up and tested for hot spots and didn't find any. Can't get to much of the roof to use spray foam, any other suggestions? Seems like the more ventilation we got the worse it condensed but maybe it's just the winter setting in that has done this. It is frosted up on the sheeting now which it never did until this last freeze.

I agree that too much ventilation, if it short circuits the preferred air flow along the bottom side of the roof, can increase condensation.

It sounds like adding a vapor barrier in the attic is not possible.

You could add polyethylene sheeting on top of your current ceilings and then another layer of drywall. I am not sure how feasible that would be.

There are also paints which you can buy that do not allow vapor transmission. I assume they are oil-based.  You'd need to paint your ceilings and walls with these.

Have you call in the roofing manufacturer to look at things?  Have you checked with a ventilation / insulation company for their input?

There certainly do not appear to be any easy answers to what is going on.


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Todd E. Miller


I am available to answer any questions pertaining to residential (or other sloped) metal roofing. I have knowledge of most available products but I like to approach projects from a "needs" basis and analyze them individually. Additionally, I can answer most questions about building ventilation.


I have worked for a manufacturer of residential metal roofing since 1980. I currently serve as President and have been involved with a wide variety of projects of all types across the world.

I am a board member for Metal Construction Association, Metal Roofing Alliance, the local United Way, our church, and our son's school.

Over the years, I have had articles appear in several trade journals including RSI, Remodeling, and Qualified Remodeler.

I have a B.A. in Communications and have also completed three years of training with the E-Myth Academy.

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