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Community and Q&A

Where can I buy EPS foam board insulation?

BrianM72 | Posted in General Questions on

I’d like to insulate my walk-out basement this summer (one wall below grade, one above, one halfway), thinking of using foam board glued to the cinder block walls, with a framed wall and fiberglass or rock wool batts up against it.  

Do I have a good alternative to XPS for this application? EPS sounds great — cheaper, and much less GWP — but I can’t find unfaced EPS foam board. Seems like only XPS and polyiso are readily available. (except for faced, garage door insulation kits)

Any tips or advice much appreciated. Thanks!

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  1. Expert Member
    NICK KEENAN | | #1

    Oddly, Craigslist seems to be the most reliable option. Here's an example:

  2. Expert Member
    BILL WICHERS | | #2

    Call around to building supply houses that stock insulation, or specialty insulation suppliers. If those places don’t have stock, they’ll be able to order it for you.


  3. Expert Member
    Michael Maines | | #3

    You could also check with this manufacturer and ask them for distributors in your area:

  4. BrianM72 | | #4

    Thanks all! I’ll check those out. Also curious if you know the status of current manufacturing of XPS, I believe new lower GWP processes should be coming into play around now.

  5. Expert Member
    Michael Maines | | #5

    I have not heard any progress on revised blowing agents for XPS in the US. In Europe they have been using a low-GWP blowing agent for a while, and US manufacturers are cagey about their chemistry, but I'm sure we'll hear about it when one of them start using a less-bad blowing agent. (The change had been mandated for 1/1/2020 but the rule was struck down by an appellate court.)

  6. BrianM72 | | #6

    Thanks Michael - disappointing but not surprising.

    New sub-question, I got a proposal for spray foam sealing of the rim joists. I had about decided not to do this (and just do it myself with foam board, Great Stuff, and rock wool), but the price is coming in quite reasonable. Is my understanding correct that all spray foams now use low GPW blowing agents? Is that synonymous in practice with HFO's? If it's not the case that everyone uses them now, what can I ask my potential contractor -- simply , what blowing agents do you use?

    I greatly appreciate everyone's expertise here. I'm finding the options and details surprisingly complex for such a modest DIY project and you're all a huge help!

  7. raul4817 | | #7


    Depending on your location, Menards and homedepot both stock EPS in 4x8 sheets of varying thickness. Menards seems to be a bit better on price and variety.


  8. Expert Member
    Michael Maines | | #8

    user-7700882, while all spray foam manufacturers now have a low-GWP, HFO-blown option, many installers are still using HFC-blown foam. Some markets are ahead of others. It's a client-driven issue so it's important to ask for it. You should be able to simply ask for HFO-blown foam, but I would also ask for the product name and double check that it's actually HFO-blown. Also try to get them to show you the barrels of raw product to ensure they are using what they told you they would use. (Lessons learned the hard way...)

    Most foam companies tout that their products have "zero ozone-depletion potential." That's nothing to brag about; it just means they aren't breaking a law established over ten years ago, and not directly related to GWP.

    Construction is an interesting field. While building a house can be simple, building a good house gets progressively more complicated. That doesn't mean we shouldn't build better houses, but that it takes time to learn all of the options and potential pitfalls before they become problems.

  9. BrianM72 | | #9

    The company (weather seal) says they use Demilac products. It does look like Demilac has an HFO closed cell product. The proposal was to use an open cell spray foam (which I think is probably better for rim joists in a basement but I'm not sure), and it doesn't look like Demilac has an HFO blown open cell foam -- but again I'm not sure. I'll ask him, but very likely reverting to doing this part myself it's so straightforward.

    For the foam board on the walls (going back to original question) it looks like in-so-fast uses EPS. It's not what I had in mind but the combination of low climate impact and ease of install is pretty tempting.

  10. Expert Member
    Michael Maines | | #10

    Demilac had one of the first HFO-blown closed cell foams on the market. Unfortunately like all spray foam companies they overstate their case, claiming, "Insulate without damaging the planet." Don't believe their marketing; all foam insulation comes with significant carbon emissions, which matter more on the short term that we should be looking at and not the 100-year lifecycle they base their calculations on. But I digress...

    Open cell foam is blown with water, not a climate-damaging refrigerant, and requires about 1/4 of the petrochemical resins that make up closed cell foam. There are still carbon emissions in the resin and open cell foam is vapor permeable, which can lead to problems. But it is typically airtight when at least 2-3" thick and it's more flexible than closed cell foam, which can crack where it meets framing.

    In-so-fast does use EPS.

  11. BrianM72 | | #11

    Thank you again Michael! And no, I don't believe their hype. The field is way more complex than I appreciated. They have little incentive to present things clearly and lots of incentives (and ways) to mislead us, intentionally or not. The community here plays a really valuable role in cutting through all that.

  12. ssnellings | | #12

    I've run into a similar issue. Stucco suppliers will usually stock smaller pieces of EPS as part of their EIFS install systems, but they are almost certainly the wrong size for basement walls. None of my local lumberyard stock it.

    I had good luck reaching out to Brock White for local EPS, but I think they are regional.

    Further up the supply chain, check out Atlas/ACH Foam, Insulfoam, Styrotech, or Polymolding, LLC (I believe they are all manufacturers). They may be able to point you towards a local distributor. You might come across Universal Foam as well, I believe they are just a distributor.

  13. Expert Member
    BILL WICHERS | | #13

    Note that if you’re in an area with a menards, they stock unfaced EPS up to 2” thick. I used this material on my rim joists where I wanted a little bit more drying potential since I have foil faced polyiso on the exterior.


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