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SPI Toxic Off Gassing – Short Term vs Long Term Health Impacts

Gioia_Matthew | Posted in Green Products and Materials on

Hello All,

My fiancé and I are building a new home in MA. We are trying to build as green of a house we can with the budget we are working with. We have decided to build a slab on grade home with a polished concrete finish (very rare in the northeast), to reduce the amount of concrete, lumber, and flooring materials used in our build. Our house will be south facing and the concrete will hopefully act as a strong thermal mass the help heat the home in the winter.

Question: Spray foam health concerns?
We have been leaning towards spray foam for its strong R value and house sealing attributes. We believe this is very important part of building a green home. With that said, I have been slightly weary of the health concerns associated with using open cell spray foam. I’ve read several threads that date back to 2014 on GBA, so I was wondering what the current day perspective is on spray foam products. My core question is should I have any worries about the long term health effects of using spray foam insulation in our home? We have a new baby arriving and I think of her most when making these decisions. I already choose baby products (cribs, mattresses ect.) that are free of harmful chemicals. I want to make sure I don’t just undo all these careful decisions by blanketing our home with a potentially toxic product. I would love any thoughts or feedback on whether or not spray foam poses long term health effects and whether or not I should stay away from it.


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  1. Expert Member
    BILL WICHERS | | #1

    I'll start off by saying that I'm one of the more pro-spray foam people on this forum. I'm going to advise that you probably do NOT want to use spray foam in your build, at least not as a "do everything" insulating product. This isn't due to health concerns -- properly installed spray foam is pretty safe. The reason I'm advising against it is that it's really not necassary. I like to recommend spray foam as a niche product, best used in places where it's the only option (unvented cathedral ceilings in most cases, cut stone foundation walls, a few other oddball places).

    Since you're building a new home, you have lots of options. I would recommend exterior rigid foam -- polyiso -- which can be detailed as an exterior side air barrier, and also gets you continuous insulation on the exterior of the studs which is a BIG help for whole-wall insulating performance. I'd use either mineral wool or dense pack cellulose in the stud cavities (dense pack cellulose probably has some advantages in terms of green-ness here). I would install airtight drywall on the interior for an extra layer of protection.

    I would use XPS under the slab, and on the exterior of the slab, to keep that slab from being a big heat sink in the winter. XPS really is the best option for subslab use like this. There are some newer versions using more benign blowing agents that are becoming available, so that's something you'll want to look into.

    If you're going to have a vented attic, detail your attic floor / upper level ceiling as your air barrier, and install blown cellulose in the attic. Blown cellulose is the cheapest insulating material, and also one of, if not the, best option in this particular application. It's also very green.

    I'd use canned spray foam (great stuff) to seal wire/pipe penetrations in top plates and bottom plates of walls. That's it. You really don't need spray foam anywhere else unless you have some fancy construction details that need it.


  2. charlie_sullivan | | #2

    You are not between a rock and a hard place, needing to choose between an inferior envelope without spray foam or a toxic one with it. The people making the best, long-lasting, air tight, highly insulating envelopes aren't using spray foam.

    Spray foam is expensive, and usually leads people to compromise on R-value, whereas other insulation materials allow you to go as high as you want, for better comfort and energy efficiency, as well as lower climate impact.

    Spray foam does OK air sealing, but people using other methods usually get better air tightness, and you can expect that air tightness to last longer.

    And even though most spray foam jobs seem to work out OK with no apparent toxic outgassing, a small minority don't work out, leading to a nightmare scenario for the homeowner, with no solution other than selling at a loss and moving.

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