DIY Garage Insulation question

[Vprbite]

Some garage can get hot. Really hot. Hotter than a snakes ass in a wagon rut. But hey, it's Tucson. It has a wal unit AZ that works surprisingly well but I don't want to run that thing all summer and when I do, might as well try and help it out.

So the garage was probably built in the 60s. (No codes out here till the 80s and it's still unincorporated county. ) anyway the garage is built with planks. Like a barn. We do not build houses like that out here. Never have. Never will. Hell, it may have been a small barn at one point. My house is double wall brick. But the garage is wood plank. No attic or crawl space over the garage. On the inside of the garage, some previous owner added lots of outlets, lights, and drywall which seems have been done well. It's very well seamed and finished and painted. Now as best I can tell, between the planks and the inside drywall is...nothing. I mean just empty space. It could have originally been a carport turned into a garage (very common in these 65yr old houses out here) but it was all done well except for the lack of any insulation between drywall and outside planks.

So my question is, is there a DIY solution worth doing in there that will help? Cellulose is NOT an option because I don't trust those planks to be watertight unless I rebuilt them all and then we wouldn't be having is discussion. It seems many of the blow-in insulations are said to not work great or still leave some airflow. My thought is, hey, it's better than nothing! Or am I wrong and it is it a waste of time, energy, and money? Of course the garage door is probably the biggest culprit and will get dealt with first. Pulling and re-doing the drywall is also just a lot further than I want to go, as my plan is to add on to the garage in a few years (hopefully 10) when I feel better about it, money wise. Pulling and re-doing drywall now would be pretty intense.

FWIW, the drywall inside is all good, no holes or leaks, weak spot is the bay door. This is just about shoring up the insulation between the drywall and exterior plank wall. I think they are 1x6". Old houses aren't just homes, they are adventures : )

Thanks guys! Sorry for the long post but wanted to give you all the info.

[Camfab]

I just saw this, probably too late, but let's understand some stuff here. When you say the walls are just planks, are we talking ship lap? Is there building paper between the planks and the studs? If it's been drywalled and not weatherproofed with building paper, you've got problems. You're likely not noticing issues because your area is so dry. If you insulate and it gets wet in there, which it likely does when it rains, you'll end up with instant rot.

[ViperTony]

I can't say enough good things about spray foam insulation. Not a DIY but well worth it. I'll never any other type of insulation in a home ever again after going spray foam.

[Camfab]

I can't say enough good things about spray foam insulation. Not a DIY but well worth it. I'll never any other type of insulation in a home ever again after going spray foam.

My concern with spray foam is that it may work too good...... Let me explain. I see them spraying roof rafters with that stuff as well as basement walls, I'm sure it works amazing, but what happens if you have a roof leak. Another words, the paper between your shingles fails, and water is penetrating the plywood. You'll likely never know its occurring, because the water will be trapped between the foam and the plywood / rafters. That's a complete disaster. I love the idea for sure, but I my gut says no.

[Vprbite]

Thanks for the tips. When I say planks, I mean it's effectively like a barn. Probably started life that way 100 years ago to be honest. So your point about water is a good one. I'll have to really be careful about that.

I think what's going to be best is just replace the exterior with either siding or true brick facade (roof is beam ceiling held up with shore poles) and insulate inside there. No way to cheapey Charlie this one and not regret it later.

[BrianACR]

Sounds like it could be quite an adventure going at that project! I think you are right about your best bet being to replace the exterior with siding or whatever. I insulated my garage myself just with the fibregalss batting. Then did vapor barrier and walls. It was a bit of work but nothing I couldn't handle with one other helper. Made a huge difference in the temperature it gets in there. Now, mind you, I insulated to keep it warn in there, not cool. Don't want my Viper to get too chilly when it's -30C outside in the winter...

[ViperTony]

My concern with spray foam is that it may work too good...... Let me explain. I see them spraying roof rafters with that stuff as well as basement walls, I'm sure it works amazing, but what happens if you have a roof leak. Another words, the paper between your shingles fails, and water is penetrating the plywood. You'll likely never know its occurring, because the water will be trapped between the foam and the plywood / rafters. That's a complete disaster. I love the idea for sure, but I my gut says no.

Not really a disaster at all. If the paper under the shingles fails then the shingles are shit and/or well beyond their replacement time or some other damage occurred to the roof which should be inspected anyway. Your scenario is a rare or a never likely situation unless the workmanship and/quality of the shingles is piss poor. As for basement walls, it depends on a number of factors. I've seen way too many piss-poor concrete foundation jobs. It's a shame. I use rubber-coating layered with fiberglass mesh and covered with weeping tile on the exterior of my foundations. Nothing is getting through. This is in addition to a solid concrete pour and footing. As for drainage, do it right or go home. If your existing foundation has issues, address (outside as well inside) before finishing.

The only issue I've seen with spray foam insulation is not the spray foam itself. There are code snafus with spray-foaming the rafters/roof. In some localities, building inspectors will consider the attic livable space, no longer a cold zone, and may require HVAC to the area if it's sealed off with spray foam. My neighbor went through this with the building inspector. Then again, it looked like the stay-puff marshmallow man exploded in his attic. I didn't do my rafters, seems like a waste since the attic space is not finished anyway. I only spray-foamed my attic floor using fiberglass or blown in. Ridiculous R value.

[Vprbite]

I appreciate your input. After looking at it again, it does seem like replacing the walls with whatever looks best (probably real brick facade as the house is double brick) and then it will be done well and I don't have to "undo" anything.

Luckily, this is something I want to do, not need to do. Winter isn't an issue and I have a wall AC unit in there that makes it tolerable if I need to work on something in there. Even so, most garbage projects get out off till fall. July and August are set aside for perfecting my ability to throw pool parties and make margaritas.

[ViperTony]

Even so, most garbage projects get out off till fall. July and August are set aside for perfecting my ability to throw pool parties and make margaritas.

You have your priorities in order!

[Martin]

I'm in a similar situation - my garage was originally built in the '20s, and it's definitely not what I want permanently. For me, the problem is more the temperature swings during the winter - lots of condensation builds up on everything inside when the temperature swings, and that's just not good...

I've looked into insulating, etc., but came to the conclusion that starting over with something done right is the best long term solution. I'm a Costco whore, and I found some really cool pre-fab garages made by Barn Pros - they deliver the whole thing to you, and the people I've talked to who've put them up said they're really easy to build. They come with engineering plans for your local building department. So, for about $22k, you can get a 36'x36' garage with high walls (add the labor if you aren't going to do it yourself).