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New build calculation help

QuintonS
QuintonS Member Posts: 21
in THE MAIN WALL
IMG_3123.jpeg
IMG_3124.jpeg

Does this math look accurate? Trying to compare 1inch of closed cell spray foam + the rest as cellulose vs just doing cellulose and paying someone to air seal areas with great stuff pro.

Comments

  • GroundUp
    GroundUp Member Posts: 2,274

    .15 ACH is just about impossible to achieve and maintain. Even with tight construction and 1" closed cell, you're looking at .5 minimum on that calculator.

  • Kaos
    Kaos Member Posts: 457

    The number there is ACH natural, not ACH at 50Pa. Code min in a lot of places is 3Ach@50Pa. For a single story building you divide the number at 50Pa by aproximately 20, so code min would be 0.15ACH natural. Air tight is under 1ACH@50Pa, so 0.05ACH natural.

    @QuintonS You can get air tight much simper and cheaper than spray foam or a guy with canned foam. The best option is to tape the seams of your sheathing (something you have to do with something like Zip anyways). 1Ach@50Pa is doable with some attention to details for not much extra cost. Also almost all the extra labor is DIY, so you can do it after hours. The key is to have solid air barrier plan and make sure that air barrier is continuous across all cross section. Important details is air sealing your foundation to your sheathing and sheathing to ceiling air barrier continuity.

    P.S. Once any big obvious holes are filled, guy with canned foam is not likely to make much difference.

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