Insulating garage roof/dining room floor

[CarbonNeutral]

Our dining room is directly above our double garage - even on a day like today (40s), the floor in the dining room is freezing cold. There is insulation in the floor - how much I don't know.

I was thinking of lining the garage ceiling with the solid foam boards, but I worry about the fire issues - thoughts?

 

[szmaine]

Our dining room is directly above our double garage - even on a day like today (40s), the floor in the dining room is freezing cold. There is insulation in the floor - how much I don't know.

I was thinking of lining the garage ceiling with the solid foam boards, but I worry about the fire issues - thoughts?

How deep are the joists?
I was thinking that you could insulate between the joist with unfaced fiberglass and then cover that over the joist w/ 1/2"
blue/pink board for airsealing (tape the joints, spray foam any gaps). This would limit the mass of flammable (w/ toxic fumes) material, decrease the overall cost (vs using a couple inch thick blueboard alone) and prevent fiberglass sagging and raining down everywhere.
I do not believe by code it would need to be covered w/ sheetrock- only in a living space and areas open to a living space.
But you can find out more on the Dow website - I remember seeing it there.

 

[CarbonNeutral]

There is already the fire-rated sheet rock on the garage ceiling - I'd rather not take that down if possible.

 

[szmaine]

There is already the fire-rated sheet rock on the garage ceiling - I'd rather not take that down if possible.

Oh, well what about blown in cellulose? - see that other insulation thread, I put a link to a book I really like - book shows how to do blown in through sheetrock by drilling holes, then patch the holes. Cellulose is cheap and not the flammble/toxic fume hazard of extrudud polystyrene.

Otherwise, if you are just going to put foam over the sheetrock as proposed you should double check on the code issue -if you care. I have been using 2.5" blueboard in my basement (on sills and on ceiling), I don't care about code (house is 1840's) and loose no sleep over other issues -it works.

 

[CarbonNeutral]

Do you have any idea how effective this is when there's already an (undetermined) amount of pink insulation there?

 

[szmaine]

Do you have any idea how effective this is when there's already an (undetermined) amount of pink insulation there?

You mean pink fiberglass? If so, I remember that book says you still can - it should be able to squish in there with it if dense packed - but then again you have no way to look and see...
I can look at the book later at home if you want and give more detail if there is any...

 

[CarbonNeutral]

Hey, that would be awesome, thanks.

 

[szmaine]

Hey, that would be awesome, thanks.

Ok, talk to you later..

 

[szmaine]

Google book preview is letting me see that section without skipping important pages. In several places it mentions using a fill nozzle, instead of a long tube, when there is existing insulation. I guess I'd want to drill a test hole enough to get my hand into and feel what is already up there...if it not the whole depth of the joist or can be squished up I'd probaly entertain the idea.
But your original idea is easier that for sure.

Anyway, check it out


http://books.google.com/books?id=qe...sult&resnum=2&ved=0CAsQ6AEwAQ#v=onepage&q=how to dense pack cellulose existing fiberglass&f=false

 

[CarbonNeutral]

Interesting, thanks - makes sense to me. Certainly an option - need to do something...

 

[woodsman23]

Why not hang some foam insulation over the current ceiling drywall (as thick as you want) then resheet with more drywall??>

 

[johnn]

In a previous thread, it was discussed having blown in applied over fiberglass in an attic location. In general that was ok, except i believe it also referred to having to remove the backing on the fiberglass if it was the type with a backing.. Do you know if yours is backed or not? Would it make a difference seeing how its not an attic space?

 

[szmaine]

In a previous thread, it was discussed having blown in applied over fiberglass in an attic location. In general that was ok, except i believe it also referred to having to remove the backing on the fiberglass if it was the type with a backing.. Do you know if yours is backed or not? Would it make a difference seeing how its not an attic space?

If his is backed and installed correctly then the backing will be on the kitchen floor side - vapor barrier is correctly located on the warm side of the space. If he did blown it would fill in below the existing batts - thus no issue.

Incidently. blown in cellulose in an attic should be the bottom layer (it does a great job of filling the nooks and crannies, assisting in air sealing, which batts cannot, unfaced batts then can be layered on top for additional R-value (this done I believe when one is concerned with the weight of the cellulose needed to achieve the high R-value recommended in more northern climates - it is much denser than batts).

Edit: Someone wanting to add more R-value on top of existing batts but not wanting to take the time to remove them would increase their r-value but miss the opportunity to do valuable air sealing (prevent condensation, keep the heat in) at the penetration points (sewer stack, lights, chimney etc). If they had to remove the backing to do blown in then the batts were installed wrong anyway, paper should have been on the living space side.