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Roxul or polyisocyanurate?

David Richardson | Posted in Green Building Techniques on

I am putting together the design/spec for a deep energy retrofit of a 60’s bungalow in Calgary, Alberta. I will be applying an insulation product to the exterior of the sheathing to eliminate as many thermal bridges as possible.

As a big part of the retrofits intentions are for environmental reasons, I want to use as benign materials as is possible and fiscally reasonable. With regard to exterior insulation I am debating on either 4″ Roxul RockBoard 80 (R16.4) or 4″ of polyisocyanurate board (R24).

Issues I see with Roxul are: less R value, uses a “cured urea extended phenolic formaldehyde binder”. My issues with polyisocyanurate is it has a halogenated flame retardants. Any thoughts on which way to go?

Regards,
David

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Replies

  1. Patrick Walshe | | #1

    Hi David. We chose roxul comfortboard IS as it allows the wall to dry out, maintains its R value over time and in cold weather better and is naturally fire and pest resistant. When we sent an inquiry to Roxul about the formaldehyde question, a company spokesperson responded, "Although a formaldehyde-based organic binder is used during manufacturing, a high-temperature curing phase virtually eliminates volatile compounds. The result is no measurable free-form formaldehyde in the final product and no volatile organic compounds that can off-gas. " Another rep said that there is less formaldehyde than that in an apple. So it is a complex task of weighing that and the energy used to make the rock wool against the greenest of foams which still is a petroleum product and uses energy every step of the way as well. Here is our blog post http://agreenhearth.com/stone-wool-to-warm-the-heart-and-the-home/ and here is our GBA guest post https://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/installing-roxul-mineral-wool-exterior-walls

  2. User avatar Expert Member
    Dana Dorsett | | #2

    There's little question that rock wool would have fewer chemical issues, and it's inherently fireproof. Lower R/inch is of little consequence if you can just add more inches. R/lb may be another issue at high-R, since rock wool panels are more than 2x as heavy (even the lowest density versions), and only 65-80% the R value.

    If you can find a source of reclaimed iso from commercial re-roofing/demolition it's still greener than virgin-stock rock wool panels, since the lifecycle environmental hits from it's manufacture has already been taken, and re-use is merely extending the lifecycle.

  3. Jin Kazama | | #3

    Dana : is recycled insulation panels something that is easy to come by in the usa ?
    i've seen it mentionned a few times on this board..

    never found a single shop recycling insualtion here in quebec :(

  4. David Richardson | | #4

    Thanks Patrick, Dana, and Jin for your responses. I have had similar difficulties in sourcing recycled panel insulation here in Calgary as Jin is having in Quebec but I am still trying. In Alberta R value is important - as I type it is snowing out. The polyiso product I am looking at is IKO Ener- Air which is breathable. I am still uncertain what direction to move forwards with. TCPP used as a flame retardant in the product is a bit of an unknown but intuitively it doesn't feel right. But what happens to the formaldehyde in the baking process in Roxul? . Questions questions. Anyway thank you for your comments.

  5. David Richardson | | #5

    Thanks Patrick, Dana, and Jin for your responses. I have had similar difficulties in sourcing recycled panel insulation here in Calgary as Jin is having in Quebec but I am still trying. In Alberta R value is important - as I type it is snowing out. The polyiso product I am looking at is IKO Ener- Air which is breathable. I am still uncertain what direction to move forwards with. TCPP used as a flame retardant in the product is a bit of an unknown but intuitively it doesn't feel right. But what happens to the formaldehyde in the baking process in Roxul? . Questions questions. Anyway thank you for your comments.

  6. User avatar Expert Member
    Dana Dorsett | | #6

    Insulation Depot (http://www.insulationdepot.com/ ) will ship anywhere in the US lower 48 if you buy a truckload. I'm not sure if they're set up do it in Canada (either cross-border or in-country), but it's worth shooting them an email or giving them a call. Roofing contractors who do large flat-roofed commercial buildings almost always have some stock of dinged-up virgin-stock or reclaimed goods that they pick over for their own projects, and in my limited experience they will sometimes sell some of it off (for some financial return rather than paying to scrap it) to keep the pile from overwhelming the space.

    There are at least 3 other smaller vendors in southern New England handling reclaimed roofing foam as either a primary or side-business, but I doubt any of them would be driving to Calgary with it. :-) I never have trouble finding it in MA, but it's clear that it's easier to find here than in some other locations. On a DER I helped a friend out with last year he went through copious stacks of reclaimed roofing foam, saving many thousands in upfront cost.

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