Attached garage retrofit insulation ideas?

[aunsafe2015]

Bought a house that has an attached 2-car garage, and then separately there is an additional attached 1-car garage, but the 1-car is kind of off to the side like the attached picture. The only way to access the 1-car garage is through the garage door, and there is no living space above it. It shares one wall with the house, as pictured.

The walls and ceiling are finished with drywall and paint, but no insulation. I plan to add HVAC to the 1-car bay to use as an office/man cave type of space, or maybe a home gym.

Manual J indicates I could reasonably heat and cool it with a Mitsubishi 1-ton mini split (which actually have capacity greater, than 1-ton) even if I add zero insulation (it's about 275 SQ ft). Location is NC.

Question is whether I should insulate it or not, and if so, how? Options:

1) cut holes in drywall and inject foam or cellulose into walls. But what about the ceiling?

2) remove drywall completely and do whatever kind of insulation I want, then re-drywall.

3) feather out the existing wall with 2x4s by essentially framing new interior walls in front of the existing walls, insulate those, and install new drywall (this option would basically give me two full walls on to of each other, one insulated, one not). This would reduce the dimension of the room by 4-5" both length and width, but that doesn't really bother me. Again not sure what I would do about ceiling if I did this. I guess the only benefit of this over option 2 is not having to remove the existing drywall.

4) simply not insulate at all.

5) others?

Keys are value, simplicity, and having the finished product look decent. Any thoughts, advice appreciated!

 

[PhantomEB]

***** to say, rip it all out. Will allow you to put more electrical, etc around then redo the drywall.

 

[ct03911]

I agree with phantomEB. Open it up and do it right.
Drywall is sorta cheap.

 

[aunsafe2015]

Thanks for the input. I welcome any other thoughts as well!

 

[fabjunkie]

Phantom 's right, if you have electrical/AV wires you want to change or add. If you don't have anything you want to change other than insulation, I'd go with the cellulose blown in through holes at the top of the wall. Probably do the same thing through the ceiling.

 

[KenC]

Phantom 's right, if you have electrical/AV wires you want to change or add. If you don't have anything you want to change other than insulation, I'd go with the cellulose blown in through holes at the top of the wall. Probably do the same thing through the ceiling.

+1 on this. And think carefully before ripping all the drywall. Yeah, it's cheap, but finishing, taping etc isn't. Hard work if you DIY, and hard to find a pro that wants a small job.

On the ceiling, I'd cut an access 24" long between a pair of joists. You should be able to blow the entire ceiling from there and patch the hole. Or make the hole big enough put in an access ladder.

 

[GrayFlattop]

Adding to the parade, I'd rip it out because drywall is cheap (materials and labor) and trying to work around existing drywall and insulate via holes will take more time & result in a lot of patching and will never be as good a product.

or if you to expand that space, build new walls further out - just insulate those! Of course that will cost a lot more and require footings, permits, but heck, who doesn't want a bigger garage!

 

[EOC_Jason]

If you are going to do a man cave and do A/C, might as well rip it out, run electrical and other things how you want, run the copper and such, insulate, then re-sheetrock & paint...

It also gives you a chance to inspect what's behind the walls making sure everything else is okay and there aren't any holes or anything that would cause moisture issues.

For the attic, like someone else said, cut an access somewhere for the ceiling. Maybe frame it in with a cover so you can get back up there later for whatever reason...