Spray Foam Mystery - Insulation - Contractor Talk

Spray Foam Mystery

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Old 09-28-2015, 09:47 PM   #1
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Spray Foam Mystery

Hi all,

I built a house a year ago for a customer that we spray foamed the walls and the vaulted ceiling in the living room. We have run into a real odd situation where there is a spot on the roof where we spray foamed that the frost melts. I'll try to attach a picture to show you what I mean. We installed cardboard insulation stops up the heel and along the top chord for the spray foam guy to spray against and from there on up to the underside of the roof sheathing. It is a parallel chord truss in this area. There is approximately a 1" air space above the insulation stop to the underside of the roof sheathing. Any ideas would be greatly appreciated, we are banging our heads to try to figureout why it's doing this. We are getting the spray foam guy to come back and blow that air space full and see if that fixes it. We do have a picture from the inside that proves there is no missing spray foam. The spray foam operator is a certified BASF foam installer.

Daniel Spray foam mystery-uploadfromtaptalk1443494855732.png

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Last edited by vff9; 09-28-2015 at 10:43 PM.
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Old 09-28-2015, 10:13 PM   #2
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Re: Spray Foam Mystery

Sorry i can't help. Good idea to spray the 1" air space, though?


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Old 09-28-2015, 11:12 PM   #3
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Re: Spray Foam Mystery

spot like that is heat escaping from somewhere. I think your airspace is the least of your worries there. There is something else going on that is conducting interior heat outward. Could be the lack of airspace higher up the slope actually, not enough venting..? my quess???
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Old 09-28-2015, 11:17 PM   #4
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Re: Spray Foam Mystery

What is the r value for the insulation? What type is it? Closed or open cell. How deep are the trusses? I agree you are getting heat loss up there in that bay. You also show signs of thermal bridging in the roof. I would not close off the air space until you figure out what the is going on.
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Old 09-28-2015, 11:18 PM   #5
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Re: Spray Foam Mystery

Any possibility you have air leakage around that door allowing the warmer air to get drawn in through the soffit? There is also the possibility the foam peeled back off that rafter slightly, with the of frost peeling back enough to break the pressure boundary. That would explain why that rafter is giving more of a thermal break then any of the others as well
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Old 09-29-2015, 01:23 AM   #6
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Re: Spray Foam Mystery

Maybe foam blew through the baffle joint, mostly closing off air flow in that section ??

And maybe some sort of mini channel in the foam somehow got created by the baffle flange, or wire cluster or something ?? Maybe mini channel next to that hot rafter is now heated by the blocked section ??

What is the dark thing at the bottom of the valley? Is it just a water diverter flashing? I cant tell. Gotta just be a flashing eh.

I wouldn't foam it full as a hail mary with out knowing why either. Try scope cam up from the soffit venting to see what you can see. They are not too terrible expensive nowadays.
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Old 09-29-2015, 03:26 AM   #7
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Re: Spray Foam Mystery

Get your drywall guy and open up a 4x4 area in ceiling and see what's going on.

Good luck.
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Old 09-29-2015, 06:16 AM   #8
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Re: Spray Foam Mystery

I also think you will have to open it up. Peel out the foam and re-do it.

Off the wall idea: What if the foam wasn't given enough time to expand before they added another layer. The first layer can stay gooey. If you had a layer of gooey foam, somewhere in the middle, you would have a much lower R-value in that area.

I assume there isn't anything in the ceiling, right there. A light?

Although the guy is certified, sometimes things just happen.

Last edited by builditguy; 09-29-2015 at 06:17 AM. Reason: Thought about an opening the in the ceiling.
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Old 09-29-2015, 06:57 AM   #9
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Re: Spray Foam Mystery

A pinhole in sprayfoam can cause a patch of snow to melt on a roof. It doesn't take much.
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Old 09-29-2015, 07:06 AM   #10
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Re: Spray Foam Mystery

Leak right there or the foam pulled away from the deck.

You could pull the shingles, drill some small holes and inject foam from the top side if you want. Probably easier that pulling the drywall and repainting.
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Old 09-29-2015, 12:47 PM   #11
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Re: Spray Foam Mystery

Thanks for all the replies. We are going to try to check up that air space abit. We used purple closed cell BASF foam at an R-value of approximately R-30. Just to clarify it, we only used one insulation stop and the rest of the space is a hot roof with foam applied directly to the sheathing. So the area that's melted is the exact size of the insulation stop. The ghost line that goes up the left side is a double truss. Yes that is a water diverter flashing on the eavestrough. Initially the door was an issue with heat loss going up into the soffit but we got that adjusted too. In the middle of winter the roof is all frozen over and covered in snow, it's just late fall early winter when light frosting on the roof that it thaws like that.

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Old 09-29-2015, 07:36 PM   #12
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Re: Spray Foam Mystery

I would look at the header above that door, is it spray foamed?

Is heat and moisture going up that wall and into the truss cavity?

Are there electrical wires going up through the top plates there?

Just my experience.
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Old 10-09-2015, 09:34 PM   #13
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Re: Spray Foam Mystery

Just for a follow up, we spray foamed the air space I had referred to and touched up a couple other spots. Now the only bit of frost melting is where the double truss is creating a ghost line. I'm satisfied with the outcome and atleast the homeowner is too now.

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Old 10-10-2015, 07:48 PM   #14
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Re: Spray Foam Mystery

r-30 with closed cell is going to be about 5''.

you should not be able to see the rafter lines like the picture shows, specially with 5" of closed cell. ceiling material?


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