Garage insulating basics

[Rabbit929]

So I’ve been browsing your forum for awhile now and finally made an account because there isn’t an answer to my stupid question, assuming I’m the only one who ever asked it.

So let’s get started,

2 stall garage 25 deep by 22 wide attached. 2x6 walls and ceiling.

I’ve insulated 2 1/2 walls so far, paper back fiber glass, doing as much as I can afford at a given time with two kids.
Attached wall is 5/8 Sheetrock, the rest are gonna be 5/8 osb. The twist here is that it has a hip roof.

What I want are professional ideas. I don’t like to do anything without knowing if I will regret it or not. As far as concrete slab, to insulate or not to, spray foam in the ceiling, yay or nay, based on cost and value.
I plant to replace all doors with insulated, but I wanna TURBO INSULATE in order to make it cheap to heat. I’m getting tired of the smell of my propane heater fast. I know I can’t afford to do the slab and I shouldn’t till the remaining 10 feet of my last wall is done.
But I’ve noticed a draft from the outlets while I was painting, making me realize air infiltration in a garage built in to 50’s may be a problem.
So if you wanted to build a garage that was overkill with insulation, what would you do?

I’m so far thinking of spray foaming the ceiling, then Sheetrock to a vaulted type so the heat travels to the center to be forced back down on the slab. (I really wanna get scientific with this lol) but I’m also broke and this takes time so what you guys think?
I also live in North Dakota, 7month winters @ 50 below, summers as high as 100.

Here are the photos:

 

[sierradmax]

As far as the draft at the outlets, a cheap solution is "electrical outlet gasket insulators".

 

[Bolson32]

I spray foamed my hip roof on my detached garage. I wanted to keep the attic space though. If you are going to put in a ceiling either way you can probably get more insulation above the ceiling joists. I just wanted to keep my attic open for storage as I really could use the extra space. I paid about ~1.10 a board foot which translated to about 1200 for ~350sq ft at 3" thick. Which translates to about R-18-20.

 

[Rabbit929]

I spray foamed my hip roof on my detached garage. I wanted to keep the attic space though. If you are going to put in a ceiling either way you can probably get more insulation above the ceiling joists. I just wanted to keep my attic open for storage as I really could use the extra space. I paid about ~1.10 a board foot which translated to about 1200 for ~350sq ft at 3" thick. Which translates to about R-18-20.

I agree. I would love to keep the space and the openness of having a little extra ceiling. But would it be wise to do two coats of foam for a total of 6” to fill the roof joists?

 

[Bolson32]

I agree. I would love to keep the space and the openness of having a little extra ceiling. But would it be wise to do two coats of foam for a total of 6” to fill the roof joists?

Foam is usually charged by the board foot, which is a sq ft 1" thick. You can put as much as you want up there but yes, it would be wise to put as much as you can. I only had 2x4 rafters so they could really only put about 3-4". With 2x6 I'd definitely fill it up if you can afford it. Would be really cozy.

 

[stm317]

Closed cell foam is done by the board foot as noted. Doing several inches of thickness gets expensive quickly, so you reach a point of diminishing returns after 2 or 3 inches thick. Basically, the outermost foam does such a good job, that the inner foam doesn't have much to do, and so it's not cost effective to do much more than a couple of inches of thickness.

Often, a more cost effective approach, is 'flash and batt'. Even one inch of closed cell can seal off any air leakage or infiltration, and allow the insulation to work better. So, an inch or two of foam on the outside, and then standard fiberglass bat inside for the remaining R value.

 

[Dragfluid]

Look at my build thread to see what I did. I'm right next door to you, with same frigid temps at times.

Do you want a "cute" ceiling, or do you want to keep warm? Put in a flat ceiling , and fill it full of cellulose,,,, at least 18". That will settle to 16" for R-60.

Like I've said before about "storage" up above. The **** you put up there today, will still be there 10 years from now,,,,,,,,,,, untouched.

 

[Bolson32]

Like I've said before about "storage" up above. The **** you put up there today, will still be there 10 years from now,,,,,,,,,,, untouched.

LOL.... Yea I tend to agree. However I have a 1400sq ft house with a 1.5 car garage. A lot of my seasonal storage goes up there. Patio chairs/stools, ice fishing stuff, golf clubs, etc. I use all of them, just not all year. I need to get crafty with space.

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[Dragfluid]

LOL.... Yea I tend to agree. However I have a 1400sq ft house with a 1.5 car garage. A lot of my seasonal storage goes up there. Patio chairs/stools, ice fishing stuff, golf clubs, etc. I use all of them, just not all year. I need to get crafty with space.

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Outdoor tool shed?

 

[75gmck25]

I got a lot of the yard items and seasonal storage out of my garage by purchasing a medium-sized storage shed from HD.

In my city I don't need a permit if the shed (up to 80 square feet) is on cement blocks (no concrete pad), and it can be within one foot of the property line. It was a great way to free up floor space in the garage, and keep all the dirt from lawnmowers and shovels out of my garage work area.

Bruce

 

[Bolson32]

I'm in a similar situation as Bruce, I built a 96 sq ft stick built shed up on deck blocks. Up to 120 is allowed without a permit but 8x12 makes for very little waste. My garage is a 1.5 car. But, I have a ~700sq ft patio with a table/chairs, an outdoor kitchen with bar stools, and a wood 2x4 sectional couch that I put away at the end of the year. **** takes up room. Add in the lawn mower and snow blower and if I want to squeeze a car in the garage, I need to store some things in the rafters.

 

[Rabbit929]

Late late late update.
So now it’s cold again, and I’m back to this.

As of now I have replaced both doors with some nice insulated ones, replaced the 1 window with and insulated pane glass one, and various air sealing throughout.
Got gaskets on the outlets now as well, and a chimney vent for the eventual natural gas heater.
All that’s left is the expensive part, ceiling.

About adding a ceiling and blowing cellulose, my new door openers wouldn’t fit if I sheath the ceiling flat. I already had to notch the boards across slightly to fit, plus sheathing and blow-in would only allow about 3” of insulation where the ceiling meets the wall.

 

[Bolson32]

Yep, I'd still foam the underside of the roof. It won't be cheap, but I'd be shocked if it was over ~7-800 dollars more all said and done by the time you factor in materials for a ceiling or trying to get rigid foam into the ceiling gaps. Hire the foam and get on with it.

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[PhantomEB]

From the time I got my attic blown in with R60,I have said from here on in......ceiling will always get done first. I never seen my garage so efficiently heated from then on. Vapour barrier between the insulation and drywall. Definitely look into the formed plastic pieces that get placed behind the outlets and sealed off with tuck tape.

Once ceiling is done with OSB then a real heater can be thrown in and the lower stuff can happen.

 

[Bolson32]

From the time I got my attic blown in with R60,I have said from here on in......ceiling will always get done first. I never seen my garage so efficiently heated from then on. Vapour barrier between the insulation and drywall. Definitely look into the formed plastic pieces that get placed behind the outlets and sealed off with tuck tape.

Once ceiling is done with OSB then a real heater can be thrown in and the lower stuff can happen.

He won't have that room with a hip roof.

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[theoldwizard1]

Rule one of insulation. Heat rises. Insulate the ceiling/roof first and as much as is physically possible/affordable.

Rule two. Plug all cracks/holes. The area where the roof meets the wall is notoriously bad for leaks. Spray foaming this area has big benefits.

 

[Rabbit929]

From the time I got my attic blown in with R60,I have said from here on in......ceiling will always get done first. I never seen my garage so efficiently heated from then on. Vapour barrier between the insulation and drywall. Definitely look into the formed plastic pieces that get placed behind the outlets and sealed off with tuck tape.

Once ceiling is done with OSB then a real heater can be thrown in and the lower stuff can happen.

I agree 100%, in this case I did the walls first as I needed the... walls. (It was unfinished) and was unsure about how I want to go about the ceiling.
After installing the garage doors, I realized my ceiling is exactly 8ft, and I ran into clearance issues with the openers.

If it were up to me, I’d jack the whole garage up so I’d have 10ft ceilings plus 1 foot for insulation space.
For whatever reason, they put the ceiling on like in the below picture, leaving no room for a viable amount of insulation.

 

[loganb]

My 2 cents...spray the ceiling with foam and see how it is after

I recently sold a very comparable construction garage in Chicago-land, I ended up opting to redo the ceiling and redid and raised the ceiling ties to get 8' under the drywall, put in batt insulation, new rock on ceiling, new lights and painted everything white....then immediately sold. Should've fixed the ceiling long before I did any work on the walls.

Spray foaming the ceiling with 2 to 3" and leaving it exposed would be a fairly quick and not super expensive way to air seal and insulate in a single swoop. I've seen people cut and glue foam board between rafters, but unless the foam board was free and time was plentiful I wouldn't recommend this as its not as effective of a solution and will be slow....but it is better than nothing!

Assuming you leave the ceiling unfinished, I would also suggest to think about a way to circulate air as with the unfinished ceiling the heat will rise to the foam. A large ceiling fan mounted at the peak could be effective and not encroach on any of the usable wall or floor space. Maybe there is one in the house that could benefit from upgrading and put the old one into the garage? Thinking about doing that exact swap in my house...

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[Bolson32]

That's exactly what I did at my last house. 16x22 garage with 8ft walls and a hip roof didn't leave much room up there. 3" of spray foam unfinished was absolutely perfect. Gave a little light reflection and sealed everything up super nicely.

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[Rabbit929]

Maybe there is one in the house that could benefit from upgrading and put the old one into the garage?

That’s actually a really good idea.
Ceiling fan right in the middle of the peak. And pretty much all three fans in the house could use updates.

 

[loganb]

That’s actually a really good idea.
Ceiling fan right in the middle of the peak. And pretty much all three fans in the house could use updates.

It'll also help cut down the amount of stuff tempted to store in the "rafters" since that works block airflow. If it's constructed like mine was they're way too undersized for storage(but it happened anyway over the years) and there was damage as a result.

My predicament is the fan in the house likely to get replaced first I don't want in the garage either! But with high ceilings airflow is the key to comfort and keeping stratification at bay

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[banjopete]

Another option at least for tight areas at the top of the walls is to get that alone sprayed and carry on up the rest of the roof with the cheaper diy options.

Just throw up some blocking in the bays and get them to cover right up to it with foam. It doesn't have to be the whole roof.

Get some quotes, they'll likely have some minimum area they'll want but it may surprise you price wise. As others have said part of the sticker shock of spray is that it is an installed price, vs diy and there are other costs that come into play on the diy route that aren't always accounted for properly.

I've used foam elsewhere in our house and it is awesome. A little harder for me to justify for my fun garage personally.

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[rsanter]

Spray foam is by far the best.
Next choice for the roof would be the rigid foam cut to fit between rafters.

The fiberglass is good but keep in mind that for it to work there must be 6 sided contact and still air trapped in the fiberglass.

For outlets the best thing is the small can of spray foam while you have the walls open

 

[nadogail]

IMHO, any insulation is better than none. Try to stop the drafts around the outlets and add insulation in the highest heat loss areas first.