Garage Insulation

[PWilks]

I plan to basically gut my garage and re-do the electrical and insulate it, as the previous homeowner did a horrible job. I'll add a unit heater. The garage is a 3 car garage, roughly 24x36.

Other than spray foam, I've been wondering what are some of the common ways to insulate common trusses in garages?

My first thought was to run R-15 batts in the 24'' OC joist bay, and then go up above the trusses and run R-30 perpendicular to that, but here in Minnesota an R-value of 49+ is required in ceilings/attics.

Since I'll be heating it, I have to obtain that R-49 because the heater installation will be inspected. Will probably also have to pull a permit to re-do all the electrical and drywall the entire garage again.

Blown in cellulose looks ideal for the wall stud bays, but I'm gutting everything anyway, so the walls will probably just end up being an R-15 fiberglass batt.

I would also like to avoid using blown in cellulose above the finished garage ceiling, as I would like access to the attic that isn't a complete mess.

One thought was framing an additional 2x2 or 2x3 along the bottom of each truss, and then using a R-21 batt to fill the new ceiling "joist" comprised of 3.5 inches from the original truss 2x4, and 2.5 inches from the additional 2x3, allowing a R-21 batt to sit flush with the top of the joist, and then running R-30 perpendicular to that.

Any other ideas?

Thanks.

 

[nadogail]

Any amount of insulation is better than none. With blown in you could have have crawl boards to keep you out of the insulation.

 

[PWilks]

Any amount of insulation is better than none. With blown in you could have have crawl boards to keep you out of the insulation.

I obviously intend to insulate. It's just a matter of hitting that desired (and required..?) R-49 for my garage ceiling.

Thinking about it more, I might take some inch or inch and a half foam board, rip it down to an inch and a half width, and sandwich it between the bottom of the truss, and a 2x2 extension.

This would result in a "stud bay" between the joists that is 3.5 inches deep from the 2x4 truss bottom, 1 - 1.5 inch deep from the foam board, and 1.5 inches deep from a 2x2.

Screwing these together, I get a 6-6.5 inch deep bay with a thermal break in the framing. I could put R19 or R21 in this bay, and then run fiberglass R-30 batts perpendicular to this in the attic.

Not sure if this a good idea

 

[That1Guy]

This may be too little too late but what the heck...
A couple things to consider here. Before you go building a false ceiling for the depth of insulation you need, you need to consider what the load rating is on your trusses. Living in Minnesota, your snow load can, and will, be substantial. That's a lot of weight as it is. But if you go adding the additional weight of all that lumber and then storing things or walking around up there, you might find yourself in a world of hurt if the trusses fail.

But, if your trusses ARE up to the task, depending on how much room you need up there, whether it be for storage or just for occasional access to wiring or whatever, you may be able to get away with a "catwalk' type of setup. In my attic I'm nailing horizontal 2x4s from the diagonal truss webs - 20" from the ceiling panels to the top of these 2x4s to allow for that depth of blown insulation. I'll slide the 24" x 96" sheets of plywood on top of these 2x4s to create a 24" wide catwalk, above the insulation, from one end of the attic to the other. I think a catwalk like that would add a LOT less weight to your roof system than a ceiling extension would. Just a thought.

Please be sure to post back here and let us know what route you choose and how it works out for you. I'm interested to see how this unfolds. And don't forget the pictures. We all love pictures.

Best of luck.
Be well.