Looking for rigid foam without flame retardant…Help!
Carfar96
| Posted in Green Products and Materials on
I have decided to completely insulate our basement (slab and walls) with rigid foam insulation (preferably XPS). Does anyone have any recommendations of any products without flame retardants? I am trying find products that are less toxic and have less off gassing of potentially harmful chemicals. Also, any spray foam products (for sealing the cracks and joints) that you recommend that are less toxic? Thank you!!!!
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All foam insulation sold in the US has flame retardent.
XPS outgasses it's blowing agents (a mix of HFCs, predominantly HFC134a) over time, and loses performance in the process. EPS is blown with a much more environmentally benign blowing agent (pentane) most of which outgasses at the manufacturing facility, and even the residual amount left is essentially gone by the time it arrives at the distributor's warehouse. For sub-slab and exterior foundation insulation it's the least damaging foam solution.
Such a shame we don't have the mineral insulation panels available in the USA that they have in Europe. The closest equivalent would be foamglas panels, but the increased cost and labor compared to rigid foam would be high.
Thank you! How do XPS and EPS compare when used for the interior of concrete walls and on the slab? Would all spray foam insulation be a "less toxic" option?
When searching this was the only one I could find that might not have flame retardants (not XPS or EPS though and I don't know if it would be suitable for my purposes): http://www.jm.com/en/building-materials/building-insulation/commercial-residentialbuildinginsulation/ap-foil/
Caroline,
The product you linked to (Johns Manville AP foil) is polyisocyanurate. It's perfectly OK to use polyisocyanurate on the interior side of your basement walls. However, polyisocyanurate is not recommended below or above a concrete slab. Here is a link to an article with more information: Choosing Rigid Foam.
Neither XPS nor EPS is toxic, although the blowing agent used to manufacture XPS has a high global warming potential. That's why green builders prefer EPS to XPS.
Most green builders look forward to the day when flame retardants are no longer added to EPS or XPS. In the meantime, I would put this worry near the bottom of my worry list, especially since you probably aren't planning to leave the rigid foam exposed. I imagine that you are planning to cover the rigid foam with some type of finish materials.
Thank you, Martin! One other product I found was Roxul Comfortboard IS. What are your thoughts about this product? Can it be used on below grade concrete walls (interior side) or on top of the concrete slab? Also, any thoughts about Dricore instead of XPS under laminate flooring? Thank you!
Carolyn,
Many of your questions can be answered by reading articles on the GBA web site, or by using the GBA search box. Here are links to two articles you should read:
How to Insulate a Basement Wall
Fixing a Wet Basement
In the first of these two articles, I wrote, "Fiberglass batts, mineral wool batts [like Roxul Comfortboard], and cellulose are air-permeable. When this type of insulation is installed in contact with concrete, the moisture in the interior air condenses against the cold concrete surface, leading to mold and rot. That’s why I advise builders that fiberglass batts, mineral wool insulation, and cellulose should never be installed against [the interior side of] a basement wall. The risk of moisture problems is reduced if the concrete is first covered with a continuous layer of rigid foam or closed-cell spray foam. If that is done, some builders then install a 2x4 wall on the interior side of the foam insulation and fill the stud bays with fiberglass batts. This approach is less risky than installing fiberglass directly against the concrete."
In the second of these two articles, I wrote, "If you don’t want to lose the height required for rigid foam, you could try installing a dimpled subfloor product like Delta-FL. (Note that some similar products, notably DRIcore, have mixed reviews from some builders. For more information on this topic, see comment #6 from Mike Guertin, below.) While Delta-FL is worth considering, especially when the basement ceiling is already low, it's not the preferred solution. If you plan to install finish flooring in your basement, it's always better to install rigid foam insulation on the slab than to proceed without any floor insulation."
In Comment #6 on that page, Mike Guertin wrote, "When DRIcore first came out I thought it was a great idea and used it on several basement projects until the problems started - some big, some small. Panel edges swelled and the required 1/4 in. perimeter space was not enough to prevent buckling. My guess is that because the dimple mat backing on each DRIcore panel doesn't seal to the adjacent 4 panels, there can be enough moisture absorbed by the wood over time for irreversible expansion to occur. Delta-FL is a separate sheet that gets taped at joints and sealed at the perimeter. No problems in basements with Delta or other full-coverage dimple mat systems."
I think you meant "Dricore instead of either EPS or previously used XPS" ;) Again, environmentally conscious builders prefer EPS to XPS, unless you can find a source of used XPS that would have even less environmental impact. If you're looking for a source of used foam, used the Search function on this site (there are numerous threads that mention various companies supplying used rigid foam).
If you use the search terms "insulate basement walls", you'll find several links to articles on the topic, and that will give you the in-depth explanation for why you don't want to use open, fibrous insulation (e.g., fiberglass batts, mineral wool) directly against basement walls.
Good luck with your project, you will love a well insulated basement.
Thank you, Martin! It looks like we stick with rigid foam :)
...again, Martin is a faster typist...
Thank you, Andrew! We are torn between the XPS and EPS. I am just worried that the EPS won't be as durable and provide as good of an R-Value. Also, I can't find any green guard certified EPS and it still seems to have fire retardants :(
Also, any suggestions about a nontoxic canned spray foam? We will need to use the spray foam before taping to make sure all of the the joints are sealed. We will also use it above the rigid foam. Everything thing I have found looks super nasty air quality wise :(
Healthy, safe building practices are paramount but in this less than perfect world it comes down to priorities. Basement remodels in particular have their risks. If you haven't done so yet, I suggest that you develop a ranked list of concerns as you plan your basement remodel. For example:
1. Egress and fire protection; reduce fire risk and ensure occupants can flee from fire, gas leaks etc.
2. Radon; test, retest and mitigate if needed.
3. Carbon Monoxide; ensure proper operation and venting of combustion appliances in basement, install an alarm.
4. Mold; ensure moisture and water is completely controlled.
5. Ventilation; provide adequate air exchanges and introduction of fresh, filtered air.
6. VOCs; Select low emitting products (look carefully at your paints, laminated flooring, paneling etc)
7. Other material properties and concerns.
The list goes on and certainly others may propose a different order. I'm not suggesting that your concerns with foam insulation are not valid, just reminding you of the big picture and where it may fit in. Even products that are inherently low risk can cause a health or safety problem if misapplied.
Roxul has some great qualities for certain applications in your project. Formaldehyde emissions have been a concern with the product historically. Not sure if it is today. It is not a substitute for rigid foam under your flooring as it lacks compressive strength. Also, to avoid wicking it should be protected from direct contact with concrete surfaces.
Pre-made rigid foam is undoubtedly superior for air quality concerns that site-sprayed foam, but the canned foam is not exactly nasty stuff compared to two-pard sprayed polyurethane. I wouldn't worry about it, and you can always cover the spray-foamed joints with a high-quality tape after it's dry. If you're planning to cover up the foam with drywall or cementboard after it's in place, it's all largely moot anyway since these materials will separate the foam from the interior climate of the basement. Highly recommend cementboard instead of drywall at least for the first few feet since drywall is moisture-sensitive and basements can flood. And if you ever finish the basement, don't use moisture-sensitive materials like wood flooring and baseboards. Those are much bigger factors in your basement's indoor air quality than the type of foam you encapsulate behind the finished wall surface you're going to cover it with.
For many applications where you might used canned foam, another option is caulk or a non-foaming flexible sealant. Many caulks are at least as bad as canned foam from an emissions/toxicity standpoint, but there's one awesome option you can choose instead, that is excellent in both regards: Contega HF sealant imported by 475 building products. It's solvent is ethanol, so it you are OK with being in the same rooms as people consuming alcohol, this is no worse than that when it's being installed, and the odor is completely gone very quickly. I still use canned foam in many places, but where Contega works, that's my first choice.
As far as XPS vs. EPS, an EPA report I read said that EPS typically uses fire retardant at 0.5%, and XPS at 0.5 to 1%. So you probably get less of it in EPS, as well as getting less greenhouse gas emissions. And they use the same fire retardant. I think the reason you see more certifications on XPS is that XPS is made by a few large factories, whereas EPS is made by a two-step process chain. One of a few large companies makes beads in compressed form. Then more widely distributed "expanding" operations expand the beads and mold the result into various shapes including insulation boards. This two-step process reduces transportation costs, but it also means there are many small companies selling it, and they are less likely to bother with certifications.
In theory, it should be possible to buy EPS without fire retardants. Supposedly, EPS packaging material used inside cardboard boxes to protect TVs and other products, and to subsequently fill landfills, is made without fire retardants, because there is no need to meet building code requirements. Many of the same companies that make EPS insulation also make EPS packaging. If they did a run of EPS boards using the beads they usually use for packaging, they would make what you want. Given that there are many small manufacturers, you might find one willing to do that. But you might have to tell them you are using it for something other than building insulation because they might be afraid of liability if they sold it to you for building insulation.
Thank you, Charlie! That was incredibly informative and I really appreciate the sealant recommendation! Has anyone ever had any experience with EcoCell cellulose blanket insulation? Our insulation contractor recommended it today and I can't find very much in the way of real world experiences online. He suggested using the XPS/OSB for the floor, but using EcoCell on the unfinished walls without studs. He said you just put it directly on the concrete and leave it exposed. He said we could also stud it and cover it with drywall.
Carolyn,
No, you can't use cellulose insulation (like EcoCell) on the interior side of a basement wall, because cellulose insulation is air-permeable. If you read one of my previous answers (Comment #6), you'll realize that the issue has already been discussed.
EPS is the same polymer as XPS. EPS has a more durable R-value than XPS. As XPS loses it's HFC blowing agent over time, it's performance drops to that of EPS of similar density, whereas the performance of EPS is constant over time.
EPS is also cheaper per R than XPS. At any labeled R-value, 1.5lb density EPS is 20% thicker than 1.5lb density XPS. Under a slab the thickness doesn't really matter. On the exterior or interior of foundation walls it might become an issue at high-R.
But on the interior side the interior side of the foundation walls it's somewhat safer to use polyiso- it's kindling temperature is higher than EPS/XPS, and even when burning it chars in place rather than melting into a puddle of flowing burning goo. At any given R-value it's ~25-30% thinner than EPS (and thinner than XPS). Foil faced polyiso keeps any fire retardents trapped, and is a barrier against water vapor and radon as well. But you can't put polyiso on the exterior of the foundation below grade, nor under slab. If in direct contact with damp soil it will wick moisture and lose some performance.
In Europe XPS is blown with CO2, and it has the same thermal performance as EPS (both short and long term), but somewhat different moisture handling characteristics (which isn't relevant in this application.)
Using cellulose below grade is a water-logging mold farm waiting to happen, no matter how high they dose it with borates to inhibit mold.
Other ways of insulating a foundation wall would be to build the foundation itself out of aerated autoclaved concrete block, but that's going to be both more expensive to build and difficult to source in the US. A foot thick AAC block has the thermal performance of about 2-2.5" of polyiso or 3" of EPS. It would still need an inch of foam (interior or exterior) to hit code-min for basement walls in climate zone 5 or higher.
I will be using EPS or XPS below grade. But I am leaning toward the the polyiso on the walls. If there is moisture or condensation, how does the foil face polyiso react? Does it still slightly permeable like the EPS and XPS so that moisture can dry? Any issues with shrinking over time with the polyiso?
And, I am sorry for missing that point, Martin. I was told the EcoCell blankets are different than other cellulose and are made to be put on bare concrete walls.
Foil facers are impervious to water vapor or liquid water. It is not at all permeable to water vapor, and that's just fine. Concrete does not need to dry.
Since concrete can and will wick moisture, you need a good capillary break between concrete and any wood that's in direct contact with it (such as the foundation sill.) An EPDM sill gasket is the right solution for that capillary break.
Without a capillary break between the EcoCell blankets and the concrete the cellulose would wick moisture out of the foundation. The amount of moisture in the concrete can be controlled only to an extent- perfection is impossible. Also if there is even a remote chance of even minor flooding, the blankets would become saturated for several feet above the water line (probably all the way to the top) due the superior wicking properties of the material. This wicking is useful for protecting the structural wood in above grade walls, but it's a liability in basements.