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Community and Q&A

Spray foam kits

kc9azl | Posted in Green Products and Materials on

How do spray foam kits compare to pro installation?  Looking to insulate 686 square feet under the roof at 1 inch.  Was leaning toward professional but wonder what other people’s experiences are.

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  1. Expert Member
    BILL WICHERS | | #1

    The kits are very expensive for what they are. For very small jobs, the kits can come out ahead because the contractor would have such a big chunk of their bid to handle drive time and setup/cleanup. For large jobs the kits make no sense.

    I would get some bids on your project before using one of the kits. You’re at about 686 board feet which is more than the big 620 board foot kit claims, and you almost certainly won’t get what the kit claims if this is your first time using the kits. You’ll need two kits for this project. You’re into “medium size” project territory here, so a pro make be competitive with a kit. It’s worth checking.


  2. Expert Member
    Dana Dorsett | | #2

    While it's possible to do a good job with DIY kits, many DIY installers fail to follow the directions, failing to monitor or control the tank temperatures or surface temperatures where it's being applied when spraying foam. When the chemicals are leaving the tanks the pressures & temperatures drop. This becomes more of an issue when using 600 board-foot kits than with 100 board foot kits. There is a range of temperatures (for both the chemicals and the application surface) that work well, and simply keeping track of the air temperature isn't your best guide.

    The chemical temperature drop issue can be overcome by keeping the tanks in a tub of warm water when spraying.

    Most pros in my area are more expensive than kits when looking at a < 1000 board foot project. YMMV. It takes the same amount of road time and set-up & break-down time do do a 400 board foot job as it does to do a 4000 board foot job. If the roof deck project can be combined with say, a foundation-sill/band-joist sealing & insulation project to raise the volumes it may be cheaper to have a pro do it.

    If it's just the roof deck, if the roof area is 686 square feet, at a 7% framing fraction it'll take slightly more than a single 600 board foot kit to get the full 1", but if the 1" thickness isn't critical it can still deliver a good air seal and <1.5 perm vapor retardency at slightly less than an inch.

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