Looking for insulation advice for my Garage

[OnlyOneKeano]

Hey Guys

I live in Vancouver, BC. The coldest it gets here is about -5C / 23F.

I have a detached 20 x 20 unfinished Garage with 2x6 studs in the wall and 2x4 studs in the ceiling. The Garage has soffits on the sides and one roof vent. I do quite a bit of work in the garage throughout the year and in the winter it's pretty hard to work in there.

I would like to put some boards down in the attic (after I insulate) so I can use the attic for storage as it has high vaulted ceiling.

My problem is that the ceiling studs are only 2x4 so I cant use blown in because it'd only be about 3.5 inches worth. Maybe spray foam? Although I'm told thats quite expensive, or maybe fibreglass batts? what R-Value do i need?

Any advice would much appreciated

First time poster

thanks in advance

 

[#1SomeGuy]

If I remember right with 3" of spray foam you can get something like R-18. Rigid foam is around R-15 for 3". Roxul comfortbatt is R-14 for 3.5" and easy to work with and DIY. Regular fiberglass batt is R-12 for 3.5".

 

[rumpity_z28]

my garage out in hope only has r12 and it seems to work pretty well. i have stuff stored up in there as well. i use a 220 electric construction heater in there and usually let it run for a few hours before i go in there. then its nice and warm for me anyway

 

[AcroRuss]

My step father has his whole garage spray foamed. about 30' by 45'. and it does great. yeah will cost more, but more on the upfront cost will save you money in the long run. that spray is the way to go

 

[jvitez]

Is this a custom framed rafter style garage with ridge board, or do you mean 2x4 bottom cord to a factory made truss? How old is your garage? Did you build it yourself?

If it's a truss, you should check with the manufacturer as most aren't designed for an attic load in addition to the weight of the roof itself. If the load is a no-go, then blow in cellulose to a min of R30, better is R40 and you'll be toasty and happy. Use Roxul for the walls, not fibreglass: it repels water!

 

[dmsween]

I had my detached garage spray foamed. 22' x 30' x 8' ceilings roof is approx 4/12 pitch. Ceiling rafters were 2x6.

I had 3" of foam in walls and 4" of foam in rafters and it is sealed very well. I also have a 75k btu heater, which is overkill but it heats up quickly.

 

[Highbeam]

I read your description a couple of times and I believe you are describing normal trusses with a 2x4 bottom chord making a flat ceiling and you want to be able to store stuff in the triangular attic space above the ceiling. As such, you believe that you can only put in 3.5 insulation before encroaching into your "attic"?

I have a pet peeve about people storing stuff in an attic that was not designed for any loads. People's junk is heavy and since the center of the attic is taller, folks tend to store their heavy junk in the middle where the trusses are least likely to handle the load. Check on your trusses to see if they are designed for this load.

If you must use your attic for storage then you can still insulate to a depth much thicker than the 2x4, just elevate your stored **** up on shelves or a platform built into the trusswork right near the attic access. You can even construct a little catwalk so that you don't disturb the 20" or so of proper insulation.

Another option is to insulate 90% of the attic properly and then choose an area where the insulation will be thinner to store your ****.

Best yet is to store your **** somewhere else and blow in insulation properly.

 

[pmiranda]

Is this a custom framed rafter style garage with ridge board, or do you mean 2x4 bottom cord to a factory made truss? How old is your garage? Did you build it yourself?
If it's a truss, you should check with the manufacturer as most aren't designed for an attic load in addition to the weight of the roof itself.

Yep... my dad put 3/8" plywood across the rafters in his old garage and put a ton of stuff up there and it bowed within 5 years. It also had a pull-down stair that wouldn't meet code today because it wouldn't stop a fire in the garage from burning the house above

 

[OnlyOneKeano]

I read your description a couple of times and I believe you are describing normal trusses with a 2x4 bottom chord making a flat ceiling and you want to be able to store stuff in the triangular attic space above the ceiling. As such, you believe that you can only put in 3.5 insulation before encroaching into your "attic"?

The type of truss is called the 'Common Roof Truss' and its all made of 2x4, including the top chord, bottom chord, king post and truss web. Its all certified building wood and done to code. It was built new at the same time the house was built.

I have a pet peeve about people storing stuff in an attic that was not designed for any loads. People's junk is heavy and since the center of the attic is taller, folks tend to store their heavy junk in the middle where the trusses are least likely to handle the load. Check on your trusses to see if they are designed for this load.

There's no need to generalize or stereotype regarding people's heavy junk as you put it. I'm not a careless homeowner and I won't be storing anything of any significant weight up there, and IF I do, i would be sure to put it as close to the wall as I can and distribute or support the load as necessary

If you must use your attic for storage then you can still insulate to a depth much thicker than the 2x4, just elevate your stored **** up on shelves or a platform built into the trusswork right near the attic access. You can even construct a little catwalk so that you don't disturb the 20" or so of proper insulation.

This suggestion is an obvious option, however is also little more work. The reason I asked the question I did is to avoid having to add anything to my trusswork work, whether it be 2x6 to make them taller so I could fit more insulation or building shelves to elevate whatever I want to store up there. I was looking for the best R-Value of insulation at 3.5 inches whilst also trying to keep it cost effective.
Another option is to insulate 90% of the attic properly and then choose an area where the insulation will be thinner to store your ****.

Best yet is to store your **** somewhere else and blow in insulation properly.

Attached is a picture of what my trusswork looks like, so you have a better idea as my initial post may have been a bit vague.

 

[mmhouse]

Look at your truss design sheet if you have it and pay attention to the bottom chord live load (LL) rating. I'm suspecting that it will say "zero" and that means you shouldn't store anything up there. If you do you risk sagging trusses and possibly worse.

If the number is larger than zero then it's okay to store stuff up there up to that number in pounds per square foot. A typical LL designation for a residential floor is 40 lb./sq. ft. Items, especially if they're heavy, should be distributed fairly evenly and not stacked all in one or two spots.

The dead load (DL) number is how much the insulation, drywall, sheathing for floor on top and other permanently attached material can weigh per square foot in total.