Removing Spray Foam Insulation
GrahamWilliamRyan
| Posted in General Questions on
Having installed foam spray insulation in the loft in Oct 2021 in order to conserve heat and energy, we now find it condemned for moisture retention affecting the roof beams. What is the best way of removing it that would satisfy a mortgage lender, as well as not producing any environmental damage: ice- blasting, which may also affect the timbers, or using hand tools (scraping) which could leave residues in crevices and hard to reach areas?
GBA Detail Library
A collection of one thousand construction details organized by climate and house part
Search and download construction details
Replies
Do you actually have a problem here? It would be far easier to just leave the spray foam in place unless it's actually causing some kind of problem. With insulation also on the attic floor, the roof insulation doesn't really "count" towards your building insulation, but that doesn't necassarily mean it's causing problems. You could even just vent the attic normally and leave the spray foam in place, which might be the easiest option. If the spray foam isn't actually causing a problem with moisture coming in from the exterior of the roof sheathing (which is a problem that would typically indicate a problem with the roof itself (shingles, etc.), then I'd try cutting in a ridge vent and soffit vents to create a vented attic and just leave the spray foam alone.
If you absolutely have to remove the spray foam, you have to do it mechanically. It will be adhered to the roof sheathing, which is the tricky part. If you are going to put on a new roof, you might be able to cut the majority of the spray foam out with a sawzall, but it will be slow going. Any kind of blasting is going to be a problem with the insulation on the attic floor. I've heard of dry ice blasting, which might be a good option. You'll still need some way to collect the removed insulation bits so that they don't get on the attic floor though, probably some big tarps would work for that.
Bill
Many thanks for those ideas, Bill. Not being a builder myself, we will get a foam removal company in to do the job. We do have air vents. I don't know if removing it mechanically would actually leave it absolutely clean, or if dry ice- blasting would be better. It may be decided by the mortgage lender!
I'm just curious why you or the mortgage lender wants to remove the spray foam. Assuming it was installed correctly, it shouldn't be a problem to just leave it there.
Bill
We don't want to remove the foam, having only installed it in October for heating and good energy reasons. But we want to sell the house, and the buyers' surveyor has indicated that there could be moisture in the roof timbers which the mortgage company has said would not be a good investment, so we risk not being able to sell, unless we take this expensive action. So the question is hand tools or dry ice blasting - which would be more effective and acceptable?
It sounds like you have moisture accumulating in the roof structure. Is there any actual damage? If not, it might make more sense to install a sufficiently thick layer of rigid foam on the exterior. This would require re-roofing, but maybe you need to do that anyway. You could further mitigate risk by installing a ventilating dehumidifier.
There is no visible sign of any damage, and we certainly don't need a new roof. The Surveyor is assuming that Spray Foam always traps moisture and leads to eventual timber beam rot. This frightens mortgage companies into refusing to lend in case of long-term damage. The roof was retiled years back and there is no evidence of any need for repair. The irony is that Spray Foam Installers are still operating, so more Spray Foam Removal companies are springing up!
Can you provide more information on geographic location/climate zone, and type of foam (open cell vs. closed cell)?
Just so I understand: there is no sign of moisture damage, correct?. This is all predicated on the "surveyor" (home inspector or similar) saying "spray foam causes roof damage and it has to come out" essentially? To be clear, a poorly done or improperly specified spray foam job can cause damage. But by no means does spray foam mean rotten roof. BSC did a survey project for the Department of Energy covering this topic back in 2013. Spray foam roofs have been part of the building code since 2007, and there are many thousands of them out there.
BA-1312: Application of Spray Foam Insulation Under Plywood and OSB Roof Sheathing
https://www.buildingscience.com/documents/bareports/ba-1312-application-of-spray-foam-insulation-under-plywood-and-osb-roof-sheathing/view
I guess I'm not understanding this either. Should be fine there unless the roof is leaking. I'm assuming you have asphalt shingles? If so I dunno how you'd remove it without a new roof since you'd have nails through all over. Maybe some kinds walnut blasting or something similar. If there are no fasteners sticking through and it's some kinda rolled adhered roofing then maybe one of these at the right length.
https://www.sprayfoamsys.com/product/turbocutz-foam-cutting-tool-foam-saw-for-open-closed-cell-sfsturbo/
Logic Foam 205 Open Cell. An approved installer; Energy Saving Trust approved; Pre-install timber moisture 6%; dry roof checked; no repairs required.
We are not in America, but in the UK, so not as advanced, but maybe more cautious(?), Thank for all the information. The report shows that roof damage can be caused (presumably by any installation process, if due care is not taken. But there is no evidence of that in our case.
Let me offer you a potential alternative here that should satisfy a mortgage lender: get a wood moisture meter (here is one option: https://www.amazon.com/Klein-Tools-ET140-Non-Destructive-Detection/dp/B07SZX8QXH/ref=mp_s_a_1_4?crid=13AEFW1NPZALZ&keywords=wood+moisture+meter&qid=1657320817&sprefix=wood+moist%2Caps%2C144&sr=8-4), and MEASURE the moisture content in the wood. If the meter says it’s within acceptable limits, I would think that would satisfy the lender’s concerns.
I don’t know why a lender would ask about this. Spray foam under roof sheathing is fairly common in unvented roof assemblies, and it’s not known to increase risk of failure.
You mentioned you have a tile roof. Those are pretty good about air movement, which would mean your sheathing could dry outwards and the inward side could be sealed without worry. That might be something else to point out. As long as one side can dry, you don’t have a moisture trap.
Bill
Excellent points, Bill. Thank you.
Here's a YouTube video that fully presents the context of what the UK located OP is talking about: https://www.youtube.com/watch?v=jYNufQVIFfA
Especially interesting are the comments associated with the video.
Very interesting, thank you, but it doesn't seem to address the problem of long-term moisture retention by the foam leading to damage to beams and roof which scares the mortgage lenders.
I included the link to explain to United States readers the difference in the attitudes of mortgage companies in the UK and USA regarding spray foam.
There are some issues with open cell spray foam and moisture retention when used in attics. This has been documented, and is the reason that closed cell spray foam is generally recommended as the safer spray foam for these spaces. If the UK lenders are not making a distinction between the two types of spray foam, then that's a problem.
Closed cell spray foam itself isn't really a moisture issue, but it can conceal roof leaks. My attitude on that one is that you should be taking care of your roof anyway, so it shouldn't be a problem :-)
BTW, some of those comments in the video Eric posted mention how spray foam makes things so much stronger. While it does tend to act to glue things together, I would not rely on it as a structural material. If you have a structurally deficient roof, you should not use spray foam as a "fix" here -- the structure needs to be reinforced using real framing in this case, not spray foam.
I think there is a lot of bad info out there with spray foam. This "bad info" goes both ways too: some claim spray foam has nearly magical insulating abilities, but it really doesn't -- in practice, it's similar in R value to polyiso. Pretty good, but not some kind of amazing breakthrough as is sometimes claimed. It's not the only way to air seal, either. I would not recommend an "upgrade" to spray foam (from any kind of traditional batt insulation) for a new home, for example -- you'd be better off paying more attention to air sealing details and using mineral wool or high density fiberglass batts if you want good performance. You'd certainly get more performance for your money using batts and attention to detail with your air sealing.
I think risks are often exaggerated too. That doesn't mean there are none -- bad installs do happen, and open cell spray foam can be a problem with moisture if it's used improperly. Everything has pros and cons, and everything needs to be used appropriately for best performance.
In the OP's case though, the spray foam is already there, so the best option is likely to find a way to leave it alone if it's not part of an immedaite problem. Spray foam is NOT easy to remove, and I really think the only way to really completely remove it is probably to replace the structure to which it's been applied.
Bill
Bill, just to clarify re open cell -- even open cell is generally not a problem in many climate zones as long as the attic space is dehumidified and/or conditioned, correct?
Yes, a conditioned attic is much less likely to have problems. Open cell has been shown to hold on to moisture in some cases, and that's where the problem has come from. Think of a big, damp sponge acting to keep humidity levels excessively high for extended periods of time. That's why closed cell spray foam is usually recommend in attics -- it's safer because it doesn't hold on to moisture the way that open cell spray foam can. As long as the spray foam never sees high moisture levels to begin with though, it won't have anything to "hang on" to and it will be fine.
Note alse that open cell spray foam has to be in a thicker layer compared to closed cell spray foam before it works well as an air barrier too, but I don't think that really applies to your pariticular situation.
Bill
Aun Safe,
Here is an article on the damp sheathing issue: https://www.greenbuildingadvisor.com/article/open-cell-spray-foam-and-damp-roof-sheathing.
The way I read it is that the risk is higher in colder climates, but everyone who has open cell in the attic should add conditioned air and monitor humidity levels.
In the US typically goes down like this:
- Appraiser or home inspector makes note of water damage.
- Lender inquires about a cost to cure along with a roof inspection by a roofing company. The roofing company will give an estimate for needed repairs along with an estimate of the remaining life of the roof (5 yrs usually the min).
- Lender then requires that in order to proceed repairs if any must be completed as recommended by the roof inspection.
- In the US appraisers and home inspectors are in almost all cases not certified to be making more the cursory judgments with regards to the condition of a roof. In fact they usually add a disclaimer that they are not roofing professionals.