Rigid Foam Board Insulation

[tim5055]

One wall of my master bath is opposite the unfinished attic space over the garage. On the living side is 1/2 drywall and the garage side is either 1/2 or 5/8 drywall. I'm sure there is insulation in the wall cavity but this wall gets a little cool.

I was thinking about adding a layer of rigid foam insulation board over the drywall on the garage side. The pink/blue stuff at HD/Lowes.

Thoughts?

Things I should look out for?

Other options?

Thanks again for your comments!

[inspector57]

Must be covered, not left exposed due to fire/smoke issues. If you put it up, cover it with a minimum of 1/2" gypsum board (Sheetrockâ„¢) attached with mechanical fasteners. Lots of work for little gain... you might want to get someone with an infrared camera to look for the significant areas of heat loss/gain and address it in order of importance. My guess is you might have missing/fallen insulation inside the wall or air leakage which would be much cheaper to address with a little sealant and loose fill insulation installed in the existing wall.

[kurt]

I've done this for customers; it's a decent solution to the cold wall adjacent to an attic. It's not complicated, materials cheap, the foam cuts out thermal bridging completely, and it works.

I have a variation of this in my own house; it wasn't at all complicated or hard to install.

[tim5055]

Must be covered, not left exposed due to fire/smoke issues. If you put it up, cover it with a minimum of 1/2" gypsum board (Sheetrockâ„¢) attached with mechanical fasteners. Lots of work for little gain... you might want to get someone with an infrared camera to look for the significant areas of heat loss/gain and address it in order of importance. My guess is you might have missing/fallen insulation inside the wall or air leakage which would be much cheaper to address with a little sealant and loose fill insulation installed in the existing wall.

Well, covering it with drywall kills the quick and easy solution I was thinking of.

I've done this for customers; it's a decent solution to the cold wall adjacent to an attic. It's not complicated, materials cheap, the foam cuts out thermal bridging completely, and it works.

I have a variation of this in my own house; it wasn't at all complicated or hard to install.

Thanks Kurt,

Is there a foam board that doesn't have to be covered with drywall?

[Tom Raymond]

Check out airkrete.com. It's spray foam so it's not DIY but it has a zero flame and smoke spread index so it does not need to be covered. It can also be used to fill blind cavities, meaning it can be sprayed into the wall around the existing insulation.

Well, covering it with drywall kills the quick and easy solution I was thinking of.

Why? Drywall will be about a third the cost of rigid foam sheets, slightly more difficult to cut, and a wee bit heavier to maneuver in the attic. If you can safely work with foam sheets in the attic you can handle the drywall too. The bad news is that to achieve the desired flame spread index you will have to apply at least one coat of compound to the seams. The good news, no one will see the tape job.[]

[hausdok]

The bad news is that to achieve the desired flame spread index you will have to apply at least one coat of compound to the seams. The good news, no one will see the tape job.[]

Does that mean that in your area they actually sand off, prime and paint the interior of garages?

Just curious, as they do not generally as a rule do that around here and when folks from other parts of the country move here they seem to ask about it a lot.

I agree with Kurt's solution and Tom's comments. I can't imagine that we're talking about a very large area to cover in a garage attic. Adding a layer of drywall - even with a little bit of taping and mudding - won't take much time at all.

ONE TEAM - ONE FIGHT!!!

Mike

[Tom Raymond]

Does that mean that in your area they actually sand off, prime and paint the interior of garages?

Sometimes, but only the really high end stuff. If there is a drywall fire barrier it has to be taped and the nails/screws covered. If it gets more than one coat it's because the finisher likes to use a banjo, otherwise it's FG tape and a single pass with durabond 90.