Insane winter project: Heat/Cool 24' x 40' detached garage on the cheap.

So, all this talk about mini-split heat pumps has me thinking I could DIY one in the detached garage.  It's a frame structure with a concrete floor, 2x4 stud walls, and a roof, but no ceiling and no insulation anywhere.

I'd almost consider just putting in the system and letting it blow all the time I'm out there, but I feel like that would be something of a waste of money.

I could prolly sheetrock the walls myself.  I've got some experience working with the stuff, but it's an expense I'd rather avoid.   I could just staple in some insulation.  What's the least expensive option for insulating a garage?

As it is, I find the weather is an excuse to not work on projects out there 8 months out of the year.  It's either too dang hot, or too dang cold.

If you invest in the insulation first wouldn't that get you back some of the time to make the place usable in the hottest months.  Then, as cash allows, make it better for the coldest times with the addition of a heat source. 

Far out thought: Get a bunch of radiators and pump ground water through them using solar panels. Year round free heat / cool.

Otherwise just stuff fiberglass batts everywhere. Not sure there is a cheaper way. The easy button is spray foam, but that may be expensive. Depends on where you live.

1988RedT2 said:

I could prolly sheetrock the walls myself.  I've got some experience working with the stuff, but it's an expense I'd rather avoid.   I could just staple in some insulation.  What's the least expensive option for insulating a garage?

Cellulose in the attic/overhead will give you the most R value per $. Rigid foam panels (usually available fairly cheap on CL as "reclaimed") work great in walls because they offer lots of R value per inch of thickness, and they do much better at blocking wind/drafts than typical fiberglass rolls/batts which is a big part of what makes a building uncomfortable. A 1.5-2 inch thick foam panel would have an R value around 10-12 depending on the type of foam, but because it does os well at stopping air infiltration, it will make your building feel better than typical R 13 fiberglass.

In reply to STM317 :

Cellulose is blown in, right?  In the absence of any ceiling, what would you use?  Polyethylene sheeting? 

I'm leaning toward batts, as it feels more DIY friendly, if fiberglass can be considered friendly!

Edit:  Looks like I'm up to a thousand smackers just for insulation.  Plus the mini-split.

Did you read Robbie's thread using solar heat?  I'll see if I can find it. 

Edit https://grassrootsmotorsports.com/forum/off-topic-discussion/help-me-build-a-thermosiphon-solar-heater-for-my-g/144999/page1/

As suggested check your local Craigslist/ Kijiji/ FB marketplace for used foam insulation. Commercial roofs are often covered in it before the waterproof membrane and tar are applied. I got enough to do a 2400 sq ft shop for less than $400.

I've often wondered about DIY spray foam insulation. Anyone tried it?

Stampie said:

Did you read Robbie's thread using solar heat?  I'll see if I can find it. 

 

Edit https://grassrootsmotorsports.com/forum/off-topic-discussion/help-me-build-a-thermosiphon-solar-heater-for-my-g/144999/page1/

Huh.  Interesting.  Thing is, my south-facing wall is the front of the garage, which is largely comprised of three insulated garage doors, through which vehicles enter and exit my garage.  So, not ideally suited.

1988RedT2 said:

In reply to STM317 :

Cellulose is blown in, right?  In the absence of any ceiling, what would you use?  Polyethylene sheeting? 

I'm leaning toward batts, as it feels more DIY friendly, if fiberglass can be considered friendly!

 

Edit:  Looks like I'm up to a thousand smackers just for insulation.  Plus the mini-split.

Yes, cellulose is blown in. You'd need more than plastic sheeting to support the weight of any significant amount with typical truss/rafter spacing. If there are no plans for a ceiling, I'd go another route.

Perhaps rigid foam sheets could be your insulation and your ceiling in one? Polyiso foam sheets usually have a foil facing applied that would reflect quite a bit of light. 4 inch thick sheets would give you R20 or better. In VA, R38+ is suggested for ceilings, but that applies to living space, not necessarily a budget garage. R 20 would be the minimum I'd want in a ceiling though as you gain/lose most of your heat overhead.

Tom_Spangler said:

I've often wondered about DIY spray foam insulation. Anyone tried it?

I did some; went through one 200 board-feet kit. It was 90% preparation, like so many things. Once you start spraying it's messy and you have to work fast. The foam starts setting up in the gun in 30 seconds so you have to change the tip if you pause for any amount of time. Except working overhead, I found the gun was clogging every few minutes anyway. The kit comes with 10 tips. I worked very fast and used a bunch of them. The insulation has made a big difference (doing one unheated storage room that's under my bedroom, wanted to stop air infiltration and warm our bedroom a bit by thermally separating it.)

It's expensive, even DIY. Actually I don't know that it's any cheaper to DIY than to have someone do it.

Polyiso board does seem like maybe it'd be the best solution.  Uniform appearance.  Lightweight.  It'd be nice if it came plain white on one side.

1988RedT2 said:

Stampie said:

Did you read Robbie's thread using solar heat?  I'll see if I can find it. 

 

Edit https://grassrootsmotorsports.com/forum/off-topic-discussion/help-me-build-a-thermosiphon-solar-heater-for-my-g/144999/page1/

Huh.  Interesting.  Thing is, my south-facing wall is the front of the garage, which is largely comprised of three insulated garage doors, through which vehicles enter and exit my garage.  So, not ideally suited.

 

Still love it, and it's still cranking out heat, even after a summer of having the top vents plugged.

It's not t shirt weather inside though, and my shop is well insulated so if we get a warm day all of a sudden it is possible for my shop to be colder inside than outside. 

I'm trying to think of a way to do massive air exchange with the outside automatically whenever temp is more desirable outside than in. Ie when it's warmer outside than in in winter and when it's cooler outside than in in summer. But then keep the holes plugged and insulated when not exchanging air.

Not an expert, but going through this right now with my shop.

Reflect what outside heat energy you can. Insulate, insulate, insulate. Vapor barrier on inside if using any combustion to heat your space. Air gaps are your friend (free insulation) air loss is your enemy...this includes breaches where air can blow in as well as escape.

Low ceilings help retain heat and cold, but may interfere with lifts and gantries. 

Starting at the roof, a reflective panel next to the sheathing will help cut down on solar heat gain. Then an air gap, then more insulation. If you have trusses, sheeting the ceiling in and using vapor barrier on the "floor" before adding cellulose will help. Seal up all air gaps with expanding foam or caulk...or both. South facing walls can use a reflective panel next to the exterior sheathing, gap fill, air gap, more insulation, vapor barrier, sheet with OSB/drywall.

1988RedT2 said:

Stampie said:

Did you read Robbie's thread using solar heat?  I'll see if I can find it. 

 

Edit https://grassrootsmotorsports.com/forum/off-topic-discussion/help-me-build-a-thermosiphon-solar-heater-for-my-g/144999/page1/

Huh.  Interesting.  Thing is, my south-facing wall is the front of the garage, which is largely comprised of three insulated garage doors, through which vehicles enter and exit my garage.  So, not ideally suited.

 

You're in VA right?  I wonder how much heat you'd get just from a glass wall on that side. My redneck mind has the garage door opening covered in clear plastic film as an experiment. Another thing I've considered is building a stand alone heater like Robbie's. Like say a 4x8x1 foot box standing on end. Plumb the top and bottom to the garage. 

In reply to 1988RedT2 :

When we had to insulate our place in IL ~10 years ago, Menards had an annual insulation sale - I believe in the fall? Even though I wasn't ready to install it, I borrowed a box truck & bought all I needed then, and held onto it until I was ready to install. It saved us a significant $$$.

Menards has got the 11% off sale going on right now so a bag of cellulose they claim is good for 50 ft2 is eight bucks.  They rent the blower for $25.  In a garage, I'd try to install it a little thin and stretch the bags out a bit.  Blowing insulation in really isn't a bad job, unless you're standing on raw studs in an attic wearing a diving mask and blinded by dust, breathing through a garden hose, but that's another story...

I think the most bang for your buck is going to be putting ceilings and walls in.  My garage/workshop is drywalled, but the walls are empty - no insulation at all.  The mini split seems to do fine with that (haven't tried it when it's really cold though) and I could get it up to a reasonable temp with three electric space heaters before I had the mini split, and that was when it was fifteen degrees outside.  In the last house which had a two car unfinished garage the three space heaters did almost nothing.  If you're going to make the investment in drywall, it would be stupid not to insulate.

I spent some hours in the garage last weekend and finally put the snow tires on the DD.  Working in a sixty degree garage in January is just so damned nice.

If you're really trying to save bucks, there's the DIY option:  https://www.motherearthnews.com/diy/how-to-make-and-install-your-own-insulation-zmaz77ndzgoe

When i built my new shop (24' x 36' ) in 2017 I had the walls and roof spray foamed, and installed insulated garage doors.

6 months per year here in the swamp are plain miserable.  But now i have a $300 window A/C unit inserted in a wall and it easily keeps the whole shop at 71 F.

In the winter I usually don't need heat even when its ~32 outside.  Sometimes I turn on a small potable 1500 w floor heater.

The best money I've spent.  After 50 years of working in Non-A/C shops, its now easy to work.

In reply to jwagner :

It's been years ago, but when I blew insulation into the attic of our old old house it was a major PITA. The tube on the blower from Menards kept getting plugged & I remember having the thing stretched out across the yard, wrestling with it like a giant anaconda trying to get it unplugged. After about every 10-minutes of use.   

If you're putting in a ceiling, why not use batts between the truss/joists?  Cheaper and way easier than blown in. Another bonus is you can floor the ceiling above to make attic space.

Another vote for foam board insulation for walls, batts for ceiling.  Foam board is super easy to cut with a circular saw, then shove it in the wall and use spray foam to fill any gaps. Vapor barrier on top of that with a small air gap and then wall cover it.  Even easier if you have wall studs, just cut the foam boards to fit between the studs and spray foam after its shoved in.

In reply to Purple Frog :

I love Havana. I need to go back and shop antiques more. Sorry for the off topic.