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Light weight ceiling insulation and soundproofing?

Finnigan | Posted in General Questions on

I have an idea for insulation and soundproofing for a Manufactured home.  The vaulted ceiling is not rated for the weight of 5/8 Drywall.  So I propose to use a fire rated Poly iso foam on the ceiling and a light weight finish (ceiling tiles)  My question is if I would improve the soundproofing by using isolation clips and channel between the ceiling and poly iso, without the mass of drywall?
Or use a Green glue and mount the insulation board directly to the existing ceiling?  Maybe soundproofing is impossible without mass and I’m just dreaming.  The type of sounds targeted are both impact (rain on the roof) and road noise (tires and exhaust).  I  intend to decouple the walls and add drywall to them.  Windows are already double pane, but I will add an internal plexiglass pane to help with sound transmission.  The concern is only for one bedroom.  Comments?

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  1. Expert Member


    Why not use 1/2" ultralight drywall, which is rated for 24" spans on ceilings? It's about half the weight of the 5/8".

    1. Expert Member
      DCcontrarian | | #2

      The conventional wisdom is that heavier surfaces block more sound transmission.

      1. Expert Member
        MALCOLM TAYLOR | | #4


        Yes. I was just suggesting an alternative to using ceiling tiles as a light weight finish under whatever insulation/sound attenuation assembly he chooses.

  2. freyr_design | | #3

    Why not add a few extra supports to your ceiling to allow it to support 5/8" drywall. I would be worried about my roof if it could not support drywall.....

    for noise transmission, the addition of resilient channel helps, dense pack helps, but can be heavy. ccSPF I have found stiffens and helps with noise transmission.

    5/8" drywall weighs 2.2 pound/sf, if that is going to make or break your ceiling I think something is wrong, but maybe that normal for manufactured homes?

  3. Finnigan | | #5

    The scissor truss system is made up of 2X3s. I have already added the weight of a metal roof over. There is the original 1/2" lightweight Gypsum board on the ceiling now. There was originally 12" of Fiberglass batt in the vaulted ceiling 30 years ago. I have heard of others getting away with adding 1/2" drywall to cover the popcorn ceilings and getting away with that much extra weight. 5/8" is definitely not recommended. Thus my thoughts of the light weight fire rated poly iso. My primary question is if decoupling will help with sound transmission without the mass of additional drywall. I don't want to sacrifice the ceiling height without the benefit of some soundproofing. I have seen Sound clips and resilient channel put over existing drywall and rockwool or fiberglass installed in between the layers to soundproof, but never without the mass of 5/8" drywall.

    1. Expert Member
      MALCOLM TAYLOR | | #6


      In general decoupling helps with structure borne sounds, so it may reduce the rain noise, but will have less effect on traffic.

  4. Expert Member
    BILL WICHERS | | #7

    You need MASS (which is similar to weight) to damp sound. ISOLATION helps too. Ideally you need BOTH, working TOGETHER, to really keep sound from getting through. Isolating the interior ceiling using something like hat channel and clips will certainly help, but the lightweight ceiling material will greatly reduce the overall effectiveness of the assembly. I would try to beef up the structure enough to allow at least one layer of 5/8" drywall on the ceiling, AND use hat channel. Normally my preference would be two layers of 5/8" drywall and no hat channel, but in your case, the hat channel will be lighter weight, so I'd try that instead of a second layer of drywall.


    1. freyr_design | | #8

      I would only add that air sealing is a major factor.

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