Sound Deadening Material for Metal Roof Assembly
rk_a
| Posted in Expert Exchange Q&A on
I’m about to install an aluminum standing seam roof. The head and ice underlayment is standard. What do you think about Enkamat for sound deadening when placed on top of underlayment and underneath metal roof?
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Replies
rk-a,
I think I would try to find an existing installation and ask how it is going before committing. The cost of the material (a bit over $2 sf.) seems pretty stiff for an average roof area. The pitch they make about ventilation might not be useful if your roof has a very low pitch. If the gap is under an inch it may not be terribly useful on higher pitch either. More to point would be how your installer would deal with the material and the clips used for your standing seam choice.
The clips as pictured in their literature shows them on top of the Enkamat, which presumes either the Enkamat does not compress or the clips are tall enough to allow for a gap under the pan area of the profile to accommodate the Enkamat thickness. I would be concerned about having the clips floating above the ice shield and sheathing. The screws would be working very differently than set down tight on the roof deck. If the clips do compress the Enkamat, then the roof panel edge profile would need to set the pan elevation high enough so as to not be acting in compression between clips. The mat does not appear to be very thick so maybe there is enough gap to not cause problems. Obviously, they sell the product and would need to have figured this out by now. Question is whether your choice of roof metal is compatible.
I am impressed that they claim a 21 db reduction in sound transmission. I have metal roofing over 8" thick nailbase over 2x12 rafters with R-19 batts between, which does not reduce the sound as much as I would expect. Maybe the Enkamat would have helped. I remain a bit skeptical of the reduction of heat transfer. Metal roofs radiate heat at the same rate on both sides so the presence of a 3/8 to 1/2 air gap would not be much of a jump. I would still advise that you be sure to use high temperature ice shield.
If you are applying metal roof over an unconditioned attic rather than an unvented cathedral roof, I would guess that the attic would provide as much or much more air gap to temper the noise.
Related follow up question, would putting exterior rigid insulation over the roof decking but below the metal roof help deaden sound in rain and hail events?
Exterior rigid won't do much if anything at all.
Part of my roof is over exterior rigid with fluffy bellow, the other part metal directly on the roof deck with spray foam+batts. Both are about the same level of sound in a rain storm.
I find this sound pleasant, so not really an issue for me but I can see how it could be a big change from someone used to a shingled roof.
The issue is to get some noise reduction you have to mechanically decouple the metal roof from the structure bellow. As long as the metal is fully fastened to the roof deck, doesn't really matter what you put inbetween, all the sound is transmitted to the structure through the mounts.
Decoupling the metal won't work because of snow load issues, so your only option is to decouple the ceiling bellow. I would look 5/8" drywall and hanging the ceiling on hat channels with resilient clips.