We have a spray foam house where the insulation is applied to the under side of the roof as you'd expect. One thing we've noticed now is that when turning the heaters on that are in the attic, there's more noise in the main living areas as there's no insulation sitting on top of the ceiling drywall to help block the noise.

Would it cause any problems to lay some RockWool or similar insulation in the areas where the heaters are to help dampen the sound?

Just don't want to solve one problem and create another. I don't think it would cause issues, but hoping someone can confirm.

ktownag08 said:

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We have a spray foam house where the insulation is applied to the under side of the roof as you'd expect. One thing we've noticed now is that when turning the heaters on that are in the attic, there's more noise in the main living areas as there's no insulation sitting on top of the ceiling drywall to help block the noise.

Would it cause any problems to lay some RockWool or similar insulation in the areas where the heaters are to help dampen the sound?

Just don't want to solve one problem and create another. I don't think it would cause issues, but hoping someone can confirm.

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i would not think you would cause a problem if you are just placing it in strategic locations. as long as you aren't messing with the environmental envelope, it should be fine.

Are your units in the attic suspended or mounted on the ceiling/attic floor framing?

They're not resting directly on the framing, but sit on feet raised up.

Foam dampeners or something solid? You could be hearing vibration in lieu of or in addition to actual system motor noise.

It's definitely system motor noise as already took care of some vibrating components and rattles.

I have a similar situation in our home. Please report back if you find a solution.

Technically you are not supposed to insulate the floor of the attic in the spray foam design. I believe it is due to humidity concerns.

Snap a picture of your setup and post it.

Absolute said:

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Technically you are not supposed to insulate the floor of the attic in the spray foam design. I believe it is due to humidity concerns.

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That's correct if he was insulating the entire attic floor and he didn't have supply and return in the attic. But he/she/they is just talking about a few batts around the unit, which shouldn't cause any issue.

There is a rock wool product specifically for interior wall use to reduce sound. I'd imagine using it near/under the heater only would help and not cause other issues.

https://www.lowes.com/pd/ROCKWOOL-SAFE-n-SOUND-R-Stone-Wool-Batt-Insulation-with-Sound-Barrier-15-25-in-W-x-47-in-L/3394032

True. Doubt that it will help much if the issue is vibration. Also not sure it will help all that much doing a small area, as the attic is basically a big sound chamber.

Might check the unit. Really should not be vibrating enough to cause sound issues. I see a lot of foam houses these days and do not see or hear that issue being reported. And believe me, people will report the tiniest issues with new homes.