Garage ceiling/bedroom floor insulation?

[StickyRust]

I have an attached, unheated, 2 car garage with 2x8 joists. Above the garage are 3 bedrooms and 2 bathrooms. I just finished removing ~R13 fiberglass and OSB from the garage ceiling.

I have decided to reinsulate with Rockwool.

Option #1:

1.5" EPS(that I have extra of) right up against the subfloor, caulked, then R23 5.5" Rockwool

R28.75 total insulation

Option #2:
Just install R30 7.25" Rockwool

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I really do not want to use drywall, can I perhaps just use plywood because i am using Rockwool?

Thanks!

 

[e36jon]

Out here code for garage ceilings with occupancy above is two layers of 5/8 drywall, plus a bunch of detail stuff around penetrations and such, all in the name of fire safety.

I am also using rock-wool in my similar situation for both added fire safety and better sound suppression that fiberglass. That said, by the time rock-wool is showing off it's superior fire resistance I would say the game is already lost...

 

[StickyRust]

Out here code for garage ceilings with occupancy above is two layers of 5/8 drywall, plus a bunch of detail stuff around penetrations and such, all in the name of fire safety.

I am also using rock-wool in my similar situation for both added fire safety and better sound suppression that fiberglass. That said, by the time rock-wool is showing off it's superior fire resistance I would say the game is already lost...

yeah, so the drywall is just if I want to comply with code that hasn't been in compliance for 40 some years

so my only question is the foam + rockwool or just rockwool

 

[PCustoms]

Foam, if edge sealed with canned foam, can air seal and reduce fumes and air exchange.

But don't be a cheapskate, whatever you do use 5/8 rock to bring it to code.

 

[StickyRust]

Foam, if edge sealed with canned foam, can air seal and reduce fumes and air exchange.

But don't be a cheapskate, whatever you do use 5/8 rock to bring it to code.

i.imgur.***/i04jEnh.png

It wont let me link, but replace the .*** with .com to see what I was going for

the plywood I want to use will actually be more expensive than sheetrock, i just have no desire to deal with sheetrock

 

[PCustoms]

i.imgur.***/i04jEnh.png

It wont let me link, but replace the .*** with .com to see what I was going for

the plywood I want to use will actually be more expensive than sheetrock, i just have no desire to deal with sheetrock

Yes, if you foam seal the rigid foam and then use glass or roxull you get better performance.

The 5/8 sheetrock is about fire code and life safety. Do it right.

 

[Kaizen]

Using roxul should be good with air sealing. If you have water pipes up there I’d insulate all of those with rubber insulation as well.


Sent from my iPhone using Tapatalk

 

[NUTTSGT]

As much as I don't like drywall in a garage, you really should use in this situation. I'd use all rockwool.

 

[pvanderlugt]

^^^^^... This is good info from the fire chief.... I would take his advice... like the commercial says, he has probably seen a thing or 2...