Two layers of insulation
I’m in the process of replacing some drywall in my attached dwelling unit (mother in law) and wanted to improve the soundproofing between the upstairs and downstairs. Between the floors it currently has R-30 insulation and was thinking of adding a layer a mineral (Thermafiber Fire and Sound Guard), is it ok to add two layers of insulation? Would moisture be a concern with those two layers? Aside from the proposed insulation, I’m going to add two layers of drywall and green glue between them.
Location: Seattle, WA (R-Value zone 4)
Mineral wool: https://www.homedepot.com/p/Owens-Corning-Thermafiber-Fire-and-Sound-Guard-Mineral-Wool-Insulation-Batt-15-in-x-47-in-SG-25-P3-15-47-221/303347027
Thank you,
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Replies
I don't know about the double layer of insulation but I've heard resilient Sound clips and hat channel will cut down greatly on the sound transmission along with double layer drywall and green glue.
+1 for resilient channel, just make sure you’re using the right stuff for ceilings if you go that route.
There is no issue with two layers of insulation between floors like this, but it probably won’t gain you anything noticeable in terms of sound blocking. You’ll will see MUCH MUCH more improvement with resilient channel in clips than you will adding insulation between the joists. The insulation doesn’t do much for conducted sound, you need isolation for that which is the purpose of the resilient channel system.
The double layer of drywall will help too, but be sure to use 5/8” drywall because you want the mass.
Bill
Awesome, thank you Bill and Brad for the feedback. Since I'm running out of time for this room I'm going to goo with my original plan but I'm going to start looking into the resilient channel for my living room. Thank you!