The Money Mustache Community

Learning, Sharing, and Teaching => Ask a Mustachian => Topic started by: affordablehousing on July 08, 2019, 04:48:48 PM

Title: rockwool versus fiberglass
Post by: affordablehousing on July 08, 2019, 04:48:48 PM
Forum, I took down the ceiling in a lower room to clean up old wiring and add new lights. It also gives me the chance to insulate the ceiling underneath our bedroom. They are 2x8 joists. Should I spring for rockwool or go with fiberglass? I've never used rockwool before but am excited by the sound attenuation possibilities if this lower room gets used more as a guest bedroom (likely possibility). And what thickness would you put in, 3.5" or 5.5"? This is ~250sf so the cost difference is likely ~$200 I would think.
Title: Re: rockwool versus fiberglass
Post by: electriceagle on July 08, 2019, 07:40:37 PM
Rockwool.

The difference in material cost is dwarfed by the extra labor cost/hassle if you are not satisfied with the noise attenuation properties of the fiberglass.
Title: Re: rockwool versus fiberglass
Post by: SunnyDays on July 09, 2019, 09:23:19 AM
Yeah, get the Roxul Safe and Sound  - works well and fewer itchies.
Title: Re: rockwool versus fiberglass
Post by: affordablehousing on July 09, 2019, 10:29:51 AM
Thanks all for the advice.
Title: Re: rockwool versus fiberglass
Post by: Syonyk on July 09, 2019, 12:27:11 PM
Dunno, do you enjoy working with fiberglass?  I'm sure someone, somewhere, does...

Otherwise, rock wool is nicer to work with and does a better job on sound.  The 3.5" stuff won't support between the studs overhead, the 5.5" stuff should, though you may still have to anchor it in place a bit.
Title: Re: rockwool versus fiberglass
Post by: BNgarden on July 09, 2019, 01:03:19 PM
If using rockwool (which I would also recommend and have used in two applications for sound-proofing to good effect), make sure you don't pack it in.  Just friction fit, leaving a little air space against floor above (?), and you can use multiple layers if the depth of joists allows it.
Title: Re: rockwool versus fiberglass
Post by: Dogastrophe on July 09, 2019, 01:16:48 PM
Rockwool, but I am biased as my company is a distributor of the line.  Just a note on Safe n Sound - it does not have an official R rating as it is designed for sound proofing of interior partitions.  If you go with it, keep this in mind if you have leftovers and want to use for exterior walls.