Will closed cell spray foam prevent condensation issues?

[Hobby_Man22]

Okay, so long story short, the warm interior air hits the cold underside of my metal building roof and causes condensation to rain down inside in a few areas anytime the outside air temp matches the dewpoint. Typically this only happens maybe 10 days a year in the winter time only. It's usually the worst when temps are around 32 degrees. It starts to thaw when the sun comes out. SO with that being said, will closed cell foam still get cold like the metal roof panel, or will that still get cold also? I'd also like to replace my rockwool batts back over the closed cell foam for additional sound protection as closed cell foam is horrible at blocking noise so I've been told. I don't want to hear the roof everytime it rains

 

[JBranstetter]

Okay, so long story short, the warm interior air hits the cold underside of my metal building roof and causes condensation to rain down inside in a few areas anytime the outside air temp matches the dewpoint. Typically this only happens maybe 10 days a year in the winter time only. It's usually the worst when temps are around 32 degrees. It starts to thaw when the sun comes out. SO with that being said, will closed cell foam still get cold like the metal roof panel, or will that still get cold also? I'd also like to replace my rockwool batts back over the closed cell foam for additional sound protection as closed cell foam is horrible at blocking noise so I've been told. I don't want to hear the roof everytime it rains

I believe it will stop condensation issues by acting as both an air barrier and a moisture/vapor barrier. Obviously you need to stop the warm moist air from contacting the cold underside of the metal. If you were to do it, I'd wait on installing your sound insulation and see how the spray foam does as a sound deadener. Just like expensive cars that have sound deadening material glued to the inside of the panels, the spray foam will act in a similar manner. I'm no expert, so others might have better ideas on it.

 

[dscheidt]

To stop condensation, you need to have enough foam so that the dew point is inside the foam. Consider the case where the shop is heated to 65 with ~30% humidity, which puts the dew point at about 32F. One side of the insulation assembly is 65, and as you move through it to the other side, the temperature drops, with the outside surface being the ambient temperature. the pont where the temperature is the dewpoint of the interior air has to be in the foam, otherwise there will be condensation. (even with other insulation over it, because you will have air leaks that hit the foam, and even rockwool has air infiltration. ) Depending on what temperatures you're dealing with, this is probably only a couple inches of foam, but it's more than the flash seal spray that is sometimes done.

 

[Hobby_Man22]

To stop condensation, you need to have enough foam so that the dew point is inside the foam. Consider the case where the shop is heated to 65 with ~30% humidity, which puts the dew point at about 32F. One side of the insulation assembly is 65, and as you move through it to the other side, the temperature drops, with the outside surface being the ambient temperature. the pont where the temperature is the dewpoint of the interior air has to be in the foam, otherwise there will be condensation. (even with other insulation over it, because you will have air leaks that hit the foam, and even rockwool has air infiltration. ) Depending on what temperatures you're dealing with, this is probably only a couple inches of foam, but it's more than the flash seal spray that is sometimes done.

That's my question. Is will the spray foam keep the cold outside panel from transferring to the inside where the heater is on? That's the current problem. Is my warm interior air gets passed the rockwool batts and hit that cold roof panel. Then it acts like a sweaty coke can. I do question if I reinstall the rockwool batts over the foam, will I have the same issue? I think if the spray foam blocks out half of the cold air, then I bet it will be fine. For example, it's 30 degrees outside and the interior foam is like 50 degrees. I would think that's okay.

 

[dcg9381]

That's my question. Is will the spray foam keep the cold outside panel from transferring to the inside where the heater is on?

I'll slow the surface transition to ambient, yes. Likely if you put a laser on an uninsulated metal panel, it'll be at ambient.
If you get this done, make sure they coat everything in foam, don't leave exposed beams or purlins.

I do question if I reinstall the rockwool batts over the foam, will I have the same issue? I think if the spray foam blocks out half of the cold air, then I bet it will be fine. For example, it's 30 degrees outside and the interior foam is like 50 degrees. I would think that's okay.

We just finished a garage that's Zip-R, then spray foam, then traditional bat. It works great.

Are we talking about TX? Generally we don't HRV or ERV here, but if you were up north, the foam and insulation would be a colder surface and if you're in a moist climate, you also need a device to remove the moisture.

In TX I had an uninsulated pole barn and it would definitely "sweat" during the right conditions. Subsequent shop (open cell foam) - no sweating, but it is heated/cooled (sometimes). In TX, 98% of the time we are cooling, which removes the moisture. My two mini-splits will produce a steady stream of water, quite a bit in fact...

 

[Hobby_Man22]

I'll slow the surface transition to ambient, yes. Likely if you put a laser on an uninsulated metal panel, it'll be at ambient.
If you get this done, make sure they coat everything in foam, don't leave exposed beams or purlins.


We just finished a garage that's Zip-R, then spray foam, then traditional bat. It works great.

Are we talking about TX? Generally we don't HRV or ERV here, but if you were up north, the foam and insulation would be a colder surface and if you're in a moist climate, you also need a device to remove the moisture.

In TX I had an uninsulated pole barn and it would definitely "sweat" during the right conditions. Subsequent shop (open cell foam) - no sweating, but it is heated/cooled (sometimes). In TX, 98% of the time we are cooling, which removes the moisture. My two mini-splits will produce a steady stream of water, quite a bit in fact...

My heat pump removes moisture too. i've seen the humidity at 28 percent inside. The heat pump dumps water on the ground where the outside unit is in the winter time.

 

[Hobby_Man22]

Also, everytime I get condensation on a cold day is shortly after the sun comes up. So about 8am is when the water starts dripping. I think the water is freezing up there even though it's not quite 32 degrees. Usually it's 38 and lower that it will do it and no other time. I recently had a second shop built and they complained about ice on the columns and perlins a few times even though it wasn't that cold.

 

[Hobby_Man22]

Basically this is only a December through Feb problem. The rest of the year isn't a problem.

 

[locomotiveman]

Hate to tell you, BUT our Warehouse Condo LLC of 15 (40x60’s) had the builder’s crew lay down a TyPar-like condensation membrane ATOP the purlins before the metal ProPanel steel panels were screwed down. It works fantastic compared to bare exposed steel. No drips. None. Whyso?? I dunno. Retro-fit sounds damn near impossible…