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Are SIP panels really durable, or will they delaminate in time?

mtman64 | Posted in Energy Efficiency and Durability on

I’m in climate zone 5A. and tossing this question back and forth, whether to use SIP panels on a 2,700 sq.ft new construction house. My fear is the durability of the panels.

I wondered if anyone has had experience them delaminating. On the architectural drawings they specify a double studded 2 x 4 wall staggered 24 inches on center with a 2 x 8 top and bottom plates. Insulation value is R-27 with Icynene. I could get a better performing R-value with SIPs. Growing up as a framer, I’m concerned. I would appreciate your thoughts.
Pete F

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  1. GBA Editor
    Martin Holladay | | #1

    Others have wondered about the same question. Building scientist Bill Rose has often commented that we really don't know how long OSB will last, even if it stays dry.

    In Juneau, Alaska, owners of SIP homes discovered what happens to SIPs when they get wet: some roofs grew mushrooms, and some walls turned to oatmeal. Of course, if plywood sheathing gets wet, it can also rot.

    OSB-faced SIPs have been around for at least 30 years, and the oldest panels have not delaminated, as far as I know -- as long as the OSB stays dry.

  2. Jesse Thompson | | #2


    Make sure to check the detailing on your SIP supplier's panels before you accept their claim of a higher R-value. Many SIP projects built without structural timber frames to the interior are full of lumber clear through the panels at top and bottom plates, window and door openings, at structural bearing points, and often at panel edges. It's not as bad a conventional 16" O.C. stud frame, but there is usually a lot more thermal bridging than the SIP sales people like to admit.

    There is usually a large difference between the clear R-value of the panel, and the actual R-value of the wall as it will be installed. Staggered stud walls (or better, spaced double stud walls) typically have less thermal bridging and a higher true R-value for the same thickness of wall.

  3. mtman64 | | #3

    Thanks for your input, since this is not a timber frame home on the exterior walls we would structurally need to provide a lot of support beams in the sips panels. Which is exactly my concern is I'm back to the thermal bridging problem.
    It seems to me that double studded wall is the way to go, with possibly applying exterior Styrofoam to reduce the temperature difference between walls.
    It seems like a lot of lumber using double studs.


  4. user-993762 | | #4

    Galvanized Steel SIPs are impervious to the affects of water intrusion, rot, mold, termites. used for years in cold refrigeration, recent testing has shown that they exceeed OSB SIP engineering capabilities.

  5. gusfhb | | #5

    Pretty much every building system has some level of bridging at apertures. In fairness to sips I think the Alaska situation was a pretty extreme example, and 'standard construction' sees failures just as often.

    It would seem to me you could do the math on the thermal bridging, as mentioned, more bridging in your situation than is apparent at first, but I would think the sip company could give you a pretty accurate number.

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