Ceiling insulation help

[scarpozzi]

30x30 attached garage with 9.5 foot ceiling. I ran radiant floor heat, but won't typically heat/cool the space.....just ran pex for the heck of it. I insulated under the slab and will be insulating the 4inch walls with R13.

The ceiling /floor joists are 16" Ijoists on 12" centers.

There's going to be a bedroom upstairs.

1. Should I insulate the ceiling of the garage?
2. If so, what r-value should I shoot for and what is the best bang for the buck? (I think spray foam may be too pricey)


Location: Tennessee....we have a few months of cold weather each year.

 

[scarpozzi]

No one?

 

[GarageWrench]

If it were me I would insulate it, it will lessen the cost of heating/cooling and you might even find it tolerable without it. I added R30 to my garage ceiling after I put in a heater and barely have to heat it on really cold days. I used the Owens Corning batts. They also have a machine available for rent if you wanted to go that route.

The fact there's a room above it isn't totally necessary, but it would also help cut down on noise and keep the room at a more consistent temp.

 

[scarpozzi]

I'm thinking making it airtight is going to be almost more important than throwing more R-value at it... I just wish spray-foam wasn't so cost prohibitive.

 

[oilslick]

I'm thinking making it airtight is going to be almost more important than throwing more R-value at it... I just wish spray-foam wasn't so cost prohibitive.

No ****, if ever something should be subsidized it is spray foam. Hell I would do the dog house!

 

[Cobra6]

I would try R30 batts over the bedroom - what kind of attic/roof ventilation do you have?
Does the bedroom take up the entire attic?

Are you thinking about putting something in the ceiling underneath the bedroom?

 

[scarpozzi]

Yes Cobra6...I'm asking about the ceiling over the garage....between the garage and bedroom. It's constructed of 16" I joists on 12" centers.

I read a few other posts from people and it seems that the biggest problem with a non-foam barrier there is simply air drafts coming from downstairs. So...typical insulation won't cut it unless I use plastic as a vapor barrier overhead.....but that could potentially hold moisture and cause mold issues in the future. I'm also going to run electrical through those I-joists (non open web), but will be drilling holes and running lights/garage door openers...

I may get a DIY kit and eat the $1300-1500 cost of laying out 1" of foam to seal as many air leaks as I can.

The roof over the bedroom is a 9.5/12 pitch on the sides with a 15 foot wide 4/12 pitch shed dormer. The structure is 30x30, so the ceiling height is like 7.5 feet at the edge of the shed dormers and I capped it at 10 feet high in the middle of the room. I've already bought 12 rolls of unfaced fiberglass R30 insulation for the upstairs

It's going to be an insulated ceiling....2x10 rafters....so probably R30 max upstairs in the ceiling.