My Minnesota garage has attic trusses, with living space above. I had blown fiberglass put in all the walls. The roof was sprayed with closed cell foam; it is vented from eave to peak. This work was done this summer and this fall I noticed that cracks in the foam have formed in several places. The cracks don’t seem to be getting longer, but might be a bit wider than when I first noticed them. The framing was dry when it was sprayed; the framing materials were not rained on during construction and the frame and it had been framed up and shingled over a year before it was insulated. The weather on the day it was sprayed was moderate, maybe 70s, with no extreme humidity. I noticed on the early days of fall, when there’d be a hard freeze overnight, frost would form on the shingles–except where the cracks are (the garage is heated to 60 degrees).
As the homeowner, I’m not impressed–the upper floor has been rocked, taped, and painted. If left as is, I expect that condensation will form where the cracks are and create a moisture/mold problem. To get at all the cracks will require ripping all the rock off the ceiling.
Has anybody else experienced this problem with foam? I’ve never heard of this before. My hunch is that it was applied wrong, but I’m not a foam expert. Is it reasonable to expect the foam guy to foot the bill for repairing the cracks and paying for new sheetrock to be hung and taped? I could post pictures if it helps any.
Brent
Replies
Brent,
Sorry to hear of your problem. I will follow up on any input others might have. I am interested in using closed cell foam so this will be most educational to me. The only input I have is, read the fine print on your warranty, and did you approach your installer about your problem? I think that your problem must be addressed soon as it could cause much condensation and rot in a short time frame.
Wishing you good luck in getting your problem resolved.
Virginbuild
Please post pictures, plus any details of the foam sprayed--manuf, density, thickness, etc.
The highest-profile house job in progress right now, in my town, a little $10 million package with a 2-car garage, has cracking issues with the foam in the roof, just like yours. Everything here from low end custom on up to the megacamps gets sprayfoam for insulation.
Problem is, it was discovered after all the inside ceiling finish was expensively done, and all roofing, some of it copper, was complete.
Shrinkage cracking can occur for numerous reasons, some of them temperature related, while some relate to mix ratio. In your case, it sounds like mix. Our local problem was likely temp related.
Here, they had test sections mounted on the roof for a while, displaying two different kinds of "structure and roof layovers." The idea was to strip all roofing, chop out most of the sheathing, do a new veneer of foam over the exposed foam, sealing all cracks, then do a roof-over using 2x6 sleepers on the structure, new sheathing, and all-new roofing and perimeter trim. Yuk.
How is it "vented from eave to peak" and insulated with foam at the same time? I am very interested, but can't picture your detailing.
Sounds like they sprayed against the baffles typically used with blown-in.
I'm dense today, I guess: How can you see cracks in the foam if it's all rocked over, taped, and painted ? Or are you saying you are assuming the foam has cracked because of the frost patterns on the shingles ?
I'm with you...the description didn't mesh with any image I could conjure up, so I asked for pix. We use foam constantly in our structures. I've seen it dry out under the sun, but I've never ever seen it crack, so I'm curious on what application could cause that.
Good questions. I don't have pics yet, but I'll attempt to provide more detail in text.I first installed cardboard chutes between the 24" on center trusses, leaving a 1" gap under the roof sheathing. The chutes vent air from the soffit area to the peak, where I have a ridge vent. The ridge vent runs the length of the garage; the soffits have vent holes the length of the garage. There are chutes in every truss space.The roof was sprayed to R40, I think. I don't offhand remember the brand of foam, but I've got it written down and I'll get it.As far as sheetrock goes, I have the upstairs (living area) walls & ceiling rocked; downstairs (garage) only the walls are sheetrocked so far. There is no sheetrock on the garage ceiling (I will be insulating and rocking this ceiling, but I don't have that done yet). So, standing near an outside wall in the garage and looking up, I can see the foam on the lower portion of the roof. I can see several foam cracks here, and they match up with frost-less areas on the roof when looking at it from outside. I suspect there's more cracks under the upstairs rock because there are other frost-less areas higher up on the roof. I haven't peeled off any of the rock to confirm this.I will try take some pics tonight, which should make this clear.Brent
>>first installed cardboard chutes between the 24" on center trusses, leaving a 1" gap under the roof sheathing.
In advance of seeing your photos, I want to wonder out loud whether those chutes are capable up supporting the foam. I know it doesn't weigh much, and maybe it even has enough rigidity to support the chutes and then some.... but the roof technique I have always read about involves spraying the sheathing directly.
Interesting direction to look. Foam is hot. It expands. If they're at R40, then they're doing 6".
Would you expect 2lb foam to sag is applied to a 24" cardboard chute? I have no sense of how rigid sprayed foam is... all I've worked with are the typical XPS panels up to 4" thick. I suppose the telling point would be cracks more or less centered between the rafters, and parallel to them.
It will probably turn out to be something else.
Think we can get the OP to open the bays and cut us a cross-section of one so we can see what happened to the foam and chute? :)Some will depend on how the foam was applied. We use successive half-inch-to-one-inch layers to get to 3" or 4". And even that gets hot. Spray enough for 6" in one shot and I don't know the effect of the heat and weight, but I don't imagine it's helpful.
My foam guy (closed cell polyureathene) tells me that it will crack if it is applied too thick and allowed to cool too rapidly. He will apply thinner layers with appropriate cooling time between layers to achieve the desired R value. I have seen him spray rafter bays (in a retro fit-roof sheathing torn off due to rot) right on vaulted ceiling drywall and he (280lb)jumped on the foam 9 about a 2 in lift) right as it cured to show its strength. It takes time to do it right But call backs take more time and money.
>tells me that it will crack if it is applied too thick and allowed to cool too rapidlyThere ya go. That fits with my notion of layering vs spraying in one shot. It's easy for the OP to tell the diff. Take a core sample and look for the striations. If it was layered, you should be able to tell.
After reading this thread I went up and carefully checked the Corbond job that was shot into the 5 1/2 rafter cavity in my attic two weeks ago. I found only one place where the foam has pulled away from the rafter and that is where the end bay was filled with one pass. Guess it's a good thing we were not sure if there was enough foam to do the job so I had them shoot the whole thing with 2" first and then go back and add another 2 1/2 until the barrels ran out. I'll fix the gap with Great Stuff.Steve.
Here are some pics of the cracks, all taken while standing on the garage floor near an outside wall, looking up at the roof. Since the garage ceiling isn't rocked, I can see the foam on the lower part of the roof, before it disappears behind the sheetrocked walls and ceiling upstairs.I think these are the only ones that can be seen directly. One of these appears to extend to the sheetrocked area and like I said before, I suspect there are others that are up higher on the roof.If you look closely at some of the pics, you can see the roof plywood--the foam has apparently adhered tightly to the cardboard vent chute and pulled it away from the truss as it separated. I had stapled the chutes on the side of each truss when I installed them.I don't know a lot about foam; is it safe to say that if any cracking was going to happen, it would've cracked by now? I mean, if these cracks are fixed, is it likely that others will develop elsewhere in the future?Brent
Edited 12/7/2006 12:33 pm ET by Brent
I believe the brand of the foam used in this case is called Demilec.
I went to their web site and looked at the brochure for rigid foam. It says, in part, "Spraying HEATLOK rigid polyurethane foams with thick sections over two inches requires careful control and considerations, in order to avoid splitting, loss of adhesion and even fire. The heat produce by the exothermic reaction of the reacting materials could cause a build up of heat within the insulation. This problem could be aggravated in cold weather. DEMILEC recommends that the foams be applied not more than two inches in a single pass and adequate time be allowed, a minimum of 20 minutes, for the heat within the foam to escape. In applications requiring multiple passes the time required between the passes should be even extended beyond the 20 minutes. In the event that the heat is not allowed to escape the temperature within the foam shall increase resulting in reduced mechanical properties and scorching. In extreme cases, a rapid application of the rigid polyurethane foam with thick sections could lead to a possible fire conditions."
Your problem appears to be splitting, and this seems to caution about a cause of that. That's consistent with everything I've seen of the foam. If that's the case--if the installer sprayed to full thickness in one pass--then it would seem to be the responsibility of the installer to remedy. The foam in the pix looks normal to me...don't see evidence of bad chemistry or mix.
Call the installer back and get their explanation and, if appropriate, remedy.
Thanks for your input.The foam guy came over and looked at it. He appears to be ready to stand behind the repairs, but we'll see. To figure out the extent of the repair needs, he wants to bring in a guy with an infrared camera to get an idea of what is going on in the sheetrocked areas.Brent
Infrared camera sounds like an excellent move. Please keep us posted on the results and resolution.
Do you think this applies to closed cell only? Or can open cell have the same problem?
Open-cell is more flexible than closed, which is rigid. (It's half the R-Value, too.) The passes are to be limited to 4"-6", but that's because of heat buildup, exothermic reaction, and the potential for substrate deformation from the heat. Haven't seen a mention of splitting, so I'll say, "I don't know, but it appears the problems from too-thick passes are primarily from the heat, rather than splitting/separating."
Interesting thread, I wonder what the outcome is/was
Still pending. I'll update when something happens.Brent
http://forums.taunton.com/n/mb/message.asp?webtag=tp-breaktime&msg=83001.1 seems similar. I wonder about the frequency of installers over-filling bays in one pass. That could taint the reputation of a good product.
Here are some pics of the similar foam cracking situation that exists in my town. We had a fresh 1-incher this morning, and the heat leaks are all quite visible. Not my job.
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Oh man that's fugly. Naturally all of the interior ceilings are vaulted and done with 1x6 t&g clear cedar.
Cedar is probably the least expensive species of the ceiling planking being used inside, if any cedar is being used at all.
Update--the foam guy stopped by last night. After the holidays, they're going to tear down the sheetrock and inspect the entire roof. If there are numerous cracks found under the rock, they'll tear out all the insulation and spray it again. If no new cracks are found, they'll repair the exsisting ones. The same closed cell foam will be used. Either way, when finished, they'll pay for the foam repair/respray, new sheetrock, hanging and taping.So why is it cracking? I was told that sometime in the last year, foam companies started using closed cell foam that had a different chemical makeup than the same foam used to have. Supposedly, this affected the spraying characteristics of the foam, in increasing the amount of heat generated in the chemical reaction of the A and B components. This is consistent with what CloudHidden mentioned earlier in this thread. I think I'm going to discuss this further with the foamer, and see if he can layer it better and allow more cooling time between layers.I'm happy to see that it looks like the foam guy is going to stand for a proper repair job. I have a few questions at this point, though. I had personally installed cardboard chutes in this roof, fully venting the entire roof deck. The chutes spanned from one truss to the other, with a 1" air gap under the sheathing. Now, with the repair, the foam guy doesn't want to spray on cardboard chutes anymore. He wants to either 1) spray directly onto the roof deck, creating a so-called "hot" roof, or 2)(if I insist on a vented roof) install relatively narrow (12-16"?) styrofoam chutes that are stapled to the roof deck in the middle of the truss space (24" O.C.). This latter option leaves exposed a few inches of roof deck on either side of the chute for the foam to adhere securely to. The styrofoam chutes seem kind of kludgy; I guess I'm not wild about either option. I had thought that the fully vented solution I had (have) was the best option, short of making vents out of 1x strips and plywood. Your thoughts?Brent
>I was told that sometime in the last year, foam companies started using closed cell foam that had a different chemical makeup than the same foam used to have.Yes, the blowing agent was changed for environmental reasons. That has not made the chemistry easier. Regardless, they should foam in layers--at least 2, better 3. Glad they're standing behind the installation.No advice on the chutes. Not my area of experience. Others will have better advice.
Most codes do not allow a hot roof without an ICC report based on a large scale test. If it is allowed It could be ok, I personally do not like hard foam against roof decks. They can trap water in the sheathing allowing roof failure without any signs on the interior.Additional framing could be added within the roof system for the foam to bond to. Cardboard can pull away and allow the foam to move as it cures. The hard foam we spray(rarely) is a 2" build per layer max, second coat after cool. Any heat trapped will over blow the foam and it will eventually shrink and crack. Good luck,Garettps- I'm glad to hear the "foam guy" is standing behind his work.
Just an update--due to the cold weather, the rework got rescheduled to April, when the weather's warm. The foam guy was concerned about frost forming on the roof deck once the old foam was torn out. He didn't want to have any frost there when spraying. So, we'll see what happens in April.Brent
Are the frostless areas on the outside of the roof lining up with the cracks in the foam or with the rafters? With a light frost, it is common to see where every rafter is if the attic is heated or has heat leaking into it from below, because of thermal conduction of the wood. With the R value of wood at something like 1.2/inch and closed cell foam at 6.5 (aged), and with a 5.5 inch width of the rafter (24" OC) less the 1 inch vent gap, the R of the roof, averaged over the loss through foam and the wood calculates to be 24.1, plus whatever little the sheathing, shingles, and drywall provide.