DIY Home Improvement Forum banner

1 - 12 of 12 Posts

·
Registered
Joined
·
41 Posts
Discussion Starter #1
Hey I have a small bathroom renovation coming up and just wanted an opinion on insulation. So I have 2 walls which face the exterior of the house and i wanted to know if it would be okay to use foam board to fill in the stud cavities as my insulation as that would be a good air sealing insulation,before I put up sheetrock/cement board. And on the 2 interior walls can I use roxul as insulation or should I use some kind of kraft faced fiberglass there? If anyone can share some knowledge it would be greatly appreciated thank you
 

·
Registered
Joined
·
41 Posts
Discussion Starter #3
roxal would be fine for all of it but you can use foam board if you want, just make sure you seal the edges.


Thank you do you think it would be fine to use the foam board on the interior walls also or I should just stick with the roxul
 

·
Naildriver
Joined
·
10,421 Posts
As Neal said, Roxul (Rockwool) would be fine for all the walls and a lot less expensive than XPS. No sealing will be needed and it gives you an R15 insulation factor for 2x4 walls.
 

·
Registered
Joined
·
41 Posts
Discussion Starter #5
As Neal said, Roxul (Rockwool) would be fine for all the walls and a lot less expensive than XPS. No sealing will be needed and it gives you an R15 insulation factor for 2x4 walls.
Its a really small bathroom so I’m not really worried about the cost and I just dont want to have mold issues later on. But with the roxul do I have to put up some kind of vapor barrier?
 

·
Naildriver
Joined
·
10,421 Posts
Roxul is waterproof, mold proof, fireproof, vermin proof and needs no vapor barrier. Win-Win.
 

·
Registered
Joined
·
12,486 Posts
Roxul is waterproof, mold proof, fireproof, vermin proof and needs no vapor barrier. Win-Win.
In cold climates with real winters any batt insulation that air can move through needs a vapour barrier on the warm side. Especially in a bathroom. Air moves through, hits cold exterior surface (cold due to the insulation), moisture condenses.

The vapour barrier is also really important for reducing air leakage - relying on finish materials - drywall/trim isn't nearly as good.

Best method depends on climate.
 
  • Like
Reactions: Nealtw

·
Registered
Joined
·
41 Posts
Discussion Starter #9
Roxul is waterproof, mold proof, fireproof, vermin proof and needs no vapor barrier. Win-Win.
In cold climates with real winters any batt insulation that air can move through needs a vapour barrier on the warm side. Especially in a bathroom. Air moves through, hits cold exterior surface (cold due to the insulation), moisture condenses.

The vapour barrier is also really important for reducing air leakage - relying on finish materials - drywall/trim isn't nearly as good.

Best method depends on climate.
So are u saying that I should use a vapor barrier with the roxul? One of the reasons I was thinking of using the foam board on the exterior walls was because of its air sealing properties and that way the warm air wouldn’t be reaching the cold air during the winter. I am located in Nyc so our winters are up n down some are colder than others
 

·
Registered
Joined
·
12,486 Posts
Yes. I would use a vapour barrier in ny when any kind of batt insulation is used.

Be sure to seal the seams with tuck tape and seal the barrier to the top and bottom of the framing.

Like I said before, the insulation actually makes the exterior surface be is sheathing, brick colder so you can run into condensation issues insulating without doing any air sealing.

Now roxul board or foam board, cut to fit between the studs with gaps sealed with foam don't need vapour barrier, there's no opportunity for air movement.
 

·
Registered
Joined
·
41 Posts
Discussion Starter #11
Yes. I would use a vapour barrier in ny when any kind of batt insulation is used.

Be sure to seal the seams with tuck tape and seal the barrier to the top and bottom of the framing.

Like I said before, the insulation actually makes the exterior surface be is sheathing, brick colder so you can run into condensation issues insulating without doing any air sealing.

Now roxul board or foam board, cut to fit between the studs with gaps sealed with foam don't need vapour barrier, there's no opportunity for air movement.

Ok thank you for all the helpful info!!
 

·
Registered
Joined
·
741 Posts
With my master bathroom I added blocking for installation of grab bars and this cut the bays into small sections. I used 2-part closed cell spray foam to put down an average of 3 inches of foam for an approximate R-16. If I had used fiberglass bats the resulting R value would have been below R-7 for the wall.

I paid $400 for the two-part foam kit and applied it myself in about an hour. Very happy with the results.
 
1 - 12 of 12 Posts
Top