Polyurethane / Condensation

Quinn

I have a customer that I shingled his 2 level garage roof. My problem is the HO had a company come in and blow in polyurethane insulation and then cover that with fiberglass batts. HO called me yesterday and said roof is leaking. Turns out that when I checked behind the insulation the entire ceiling is wet. Condensation??? Has anyone else ran into a problem like this? By the way. The garage is heated with an oil furnace.

tcleve4911

Did the fiberglass batts have a vapor barrier?
Where is the water collecting?
My guess is the moisture is going through the fiberglass & collecting on the foam surface. Correct?

Why on earth would ANYONE put fiberglass over the foam?

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Quinn

Yes Fiberglass batts have paper installed towards the inside of the room. I would guess the polyurethane is 3/4" thick.

rustyjames

3/4" of the blown in is probably the reason why. From what I've been reading you need at least a couple inches if it's open cell foam. You might want to post this question at the JLC website in the building science link if you don't get a lot of responses.

Quinn

It is closed cell polyurethane.Sorry about that.

Quinn

From top down: shingles,30# felt paper,5/8 T&G osb,3/4" closed cell polyurethane, R19 papered fiberglass insulation(paper towards heated room. Condensation is between fiberglass and polyurethane foam

rustyjames

Still might not be enough foam even though it's CC. Any car's dripping wet in the garage? That would aggravate the problem.

house bldr

Is the foam sprayed directly to the roof sheathing then batts (no ventilation) is it rocked and taped,need a little more info but it sounds like a double vapor barrior issue.

jaros bros.

It's called a "flash and spray" I believe. Don't quote me on that. Contractors do it to seal a place and get away from the high cost of using only foam insulation.
The application I've heard of is only for the walls. It sounds like you have a problem with moisture building up with no place to escape. I'm not sure this is because you don't have enough insulation, but rather from the fact that the humidity is too high. The two reasons could only be hot air condensing on a cold surface or too much humidity. They are essentially the same but from a different angle. Get a tester and check it out.
At any rate, even though it might be from high humidity, there should be more insulation. Am I right about that? You are in PA and I am unaware of what the recommended insulation is for the roof.

Josh Jaros

house bldr

Flash and batt is what they call it around here

Quinn

Yes sprayed directly to sheathing then batts are applied directly underneath. No drywall has been installed yet. Would it help anything to install house wrap to the underside of the rafters even though the batts already have the paper barrier? Or should I try eliminating the paper to take care of the double vapor barrier? Hopefully the company that did the insulating will correct the problem, but I thought I would do a little research to stay ahead of the game......................Jaros> R39 is the usual recommendation here. And by the way ,we did just go through some really cold weather (-6 degrees)

Tom Struble

house wrap on the bottom

sounds like moist warm air getting around the insulations vapor barriedr try air sealing better,why would you put house wrap on the bottom of the rafters?

Leo G

Sounds to me like he has two moisture barriers, the paper and the closed cell insulation. It is getting trapped between the two with no where to escape.

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Quinn

So what are you saying Leo ? Should the paper be eliminated? My customer is checking with the company that installed it so hopefully They will have a solution tomorrow. I'll let you know what they say.

Leo G

All I know is that you should never have two vapour barriers on any one wall. Just asking for trouble. I would think that removing the paper should solve the problem. But their is a basic flaw in the way this was designed. There should be airflow allowed under the roof to keep it cool in the summer so the shingles don't bake. And in the winter to keep it cool so you don't get ice dams. But you really shouldn't be listening to me. I am a carpenter/cabinetmaker by trade. I have done my share of buiding before I settled on my current trade. I don't think the way things work have changed that much though.

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Custom Cabinets in Hartford County Connecticut

house bldr

With the ceiling not being rocked and taped and sealed with a coat of paint to much moisture is being allowed to migrate behind the insulaion where it becomes trapped between the two vapor barriors(one being the poly foam and the other being the paper on the batts)A garage is a high humidity area which doesn't help matters any.I know some people flash and batt with the paper on and don't have problems after it is finished but it seems to me it would be better to use unfaced batts.But I'm no expert on it as it is not widely used around here and opinions on it vary.

Quinn

I just talked to the HO. The Company Rep got back with him and said installing Rock should fix the problem, but he didnt say anything about taking off the paper on the batts. And he did say, They have been getting lots of calls on this.

Quinn

Thanks to all. Its nice to have an online crew to discuss things with.

Vrooman

3 major problems are no ventilation space, double vapour barrier, and insulation on the warm side of the vapour barrier (the foam). Taking off the paper may fix the problem, but you will still have insulation on the warm side of the envelope and that could still cause vapour to condensate on the foam.

Drywall will not fix this, but it will cover it up so you cant see it.

I would think the insulating contractor should know this? only fix i could see for it is spraying more foam and eliminating the fibreglass entirely.

Not your problem though if you were just the roofer!

Quinn

[quote=Vrooman;588916]3 major problems are no ventilation space, double vapour barrier, and insulation on the warm side of the vapour barrier (the foam). Taking off the paper may fix the problem, but you will still have insulation on the warm side of the envelope and that could still cause vapour to condensate on the foam.

Drywall will not fix this, but it will cover it up so you cant see it.

I would think the insulating contractor should know this? only fix i could see for it is spraying more foam and eliminating the fibreglass entirely.

Not your problem though if you were just the roofer! =quote]
I talked to the insulating company personally today and they said installing drywall will definitely fix the problem. For there sake I hope they know what they are talking about.