Researching insulation for my garage ceiling.

[little.one.der]

I have a small, two car attached garage.

It is 11' wide, and 43' long. It's a little odd, yes. It also has a flat roof which serves as a patio in the summer month that Canada usually gets.

I'm planning a reno this spring and I want to insulate it. The ceiling is 2x8, 16" on centers. I am having a tough time finding a product that will work for me.

I would like if I didn't have to add material to make them 2x10. As it is, the joists are only 98" off the floor.

Is there a batt solution I can use?

Eventually I want to drywall everything too to finish it up.

(My first garage related post ever! Feels good.)

 

[jklingel]

First off, you need to ensure that you have at least 2" of air space over whatever insulation you use, and have that open to each end. In a roof, the ratio of venting to ceiling area is about 1:200, + or -. You may need more in a flat roof, esp long and skinny like yours. I would recommend you look at mineral wool, cellulose, cotton, or wool batting; leave the fiberglass at the store. Air seal well, and you probably do not need a vapor barrier. But, if you are going to postpone the sheet rock till later, than a vapor barrier is probably a good idea.

 

[dlenkewich]

If you don't have any ventilation, which I'm assuming with there being a patio up to, there isn't, you need to fill the cavity full like you would a wall.

Go to a Convoy Supply, there should be a few in Alberta. For an 8" stud, you should be looking at an R-28, 15 inch material, it's fibreglass, Johns Manville to be exact, which they'll have or can get very quickly.

Add you vapour barrier and do up your walls and wala, your insulated.

I don't mean to point fingers, but there's a lot of incorrect information in the post above.

 

[little.one.der]

Thanks for the tip. I'll try to see if there's a Convoy Supply around here.

Is there any way to estimate what effect insulation will have on the interior temperature vs. exterior?

If I have a ceiling (480 sq ft) of R-28, three walls (790 sq ft) of R-14, and I insulate my garage door, what kind of temperatures can I expect?

If it's -25 C outside, would that be 0 C inside?

 

[dlenkewich]

It's hard to say. Just having it insulated it should keep it cooler in the summer and warmer in the winter. By how much it's hard to say. Is it tied to a house? I find that insulated attached garages leech quite a bit of heat off the house so they stay quite abit warmer then the outside air temp.

The benefit would being able to throw in a heater if you want to work in the dead of winter. It will only take a few minutes to warm up, and it will stay warm longer, so no need to burn through expensive fuel just to keep the hands warm.

 

[taskins]

Spray foam might be an option. The upfront cost is a little more though.

 

[little.one.der]

Does spray foam offer a higher R value in the same amount of space?

 

[chevy265]

If you only have 8" of space, smashing 15" of insulation into it gives you NO more r value than 8" uncrushed. I have seen alot of people waste alot of money smashing r19 into a 2x4 stud wall making it r13! 4"= r13. 6"= r19. etc.

 

[mobetta]

yes, higher R's, but less is needed because it'll stop air infiltration, sealing up the space. closed cell can be a vapor barrier, too. but then you dont get to DIY and cover yourself in itchy fiberglass. and it'll cost about 4X more than a DIY job(prices will vary)

 

[mobetta]

If you only have 8" of space, smashing 15" of insulation into it gives you NO more r value than 8" uncrushed. I have seen alot of people waste alot of money smashing r19 into a 2x4 stud wall making it r13! 4"= r13. 6"= r19. etc.

I think he's calling for 15" wide batts for 16" OC framing. defenatly
do not over compress fiberglass.

 

[little.one.der]

...it'll cost about 4X more than a DIY job(prices will vary)

I was hoping that wasn't the case.

I bet a case or two of beer and some pizzas will help my friends forget about the itchy fibers....

 

[chevy265]

I think he's calling for 15" wide batts for 16" OC framing. defenatly
do not over compress fiberglass.

Your right! Here i go shooting my mouth off before thinking. lol

 

[chevy265]

Someone correct me if im wrong but i think he DOES want some airspace above the insulation vented to the outside.

 

[little.one.der]

Like a sofit on a house? Same concept?

 

[jvitez]

If the patio is right on top of the joists, the best option would be high density closed cell polyurethane spray foam. It would act as an air/vapour barrier so no need for a ventilated "attic" space. It's also ~R7 per inch. Open cell spray foam is much lower R-value and still needs a separate vapour barrier, so I'd only go with closed cell spray foam. Just grunt and spend the $ for a professional job on this. Saving some $ on DIY and then rotting out your patio is penny wise and dollar foolish IMO.

 

[dlenkewich]

Someone correct me if im wrong but i think he DOES want some airspace above the insulation vented to the outside.

If you have ventilation available(roof vents, vented soffit), yes, you leave space for airflow.

If there is no ventilation in the space, you fill it like you would a wall.

 

[36tbird]

did I go too off topic because I did not ask a question about a garage?