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Community and Q&A

R-Max Multi max insulation noise

LincolnLong | Posted in Expert Exchange Q&A on

I have a home that has a timber framed non vented roof. Above the T&G roof decking 2 layers of R-Max insulation were installed. The layer over the T&G roof deck is 3″ of Multi-max FA3 polyiso board. The layer above is 3″ of R-Max nailable base polyiso board. Since installation of the insulation the roof has been very noisy when the time changes from night to day and when the sun hits and is removed from the roof by clouds. In other words the roof is very sesitive to thermal changes. The noises the roof makes are all over the diaphragm. The noises are much more than the once in a while pop that is normal with a timber framed roof. The roof has been exhibiting the same loud noises “rumbling, poping, cracking” since new. The noises are well above normal for what we would expect for a new correctly installed roof. We have tried many things to diagnose the problem. For example we have removed the metal roofing panels for a week leaving only the 2 layers of Rmax product. The roof still makes the same noises. When I remove the outer layer of the Rmax Nailable base, the noise stops! I have contacted Rmax support and notified them of the issue. I have not gotten any solution to my problem. Has anyone else experienced issues thermal related when using the Rmax products mentioned above in a multi-layered configuration similar to mine? I would like to add I am in climate zone 11 in Northern California.

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  1. Expert Member
    Michael Maines | | #1

    I have heard of that problem but it's rare. I imagine it's from the different layers rubbing against each other as they expand and contract with differences in temperature. Adding a slip sheet between layers, such as 6 mil polyethylene or #30 felt paper, would likely help.

    1. LincolnLong | | #2

      I agree it would help but the cost and effor to do that is $$$$$. Put this message out there to see how many other people have experienced this with the RMAX product properly installed.

  2. gusfhb | | #3

    Living for the last almost 30 years in 2 different houses with T&G large span roofs, I would say, they all do that.
    I think it is the combination of the large spans between rafters and the differential temperature . Big wind does the same thing
    They also are loud as hell in the rain.

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