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Help with insulating garage walls/foundation

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Jester966

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I have recently moved from a smaller-than-average 1-car garage, to an over-sized 2-car garage. There is a single 15amp 120v circuit in the garage, so I will be installing a 40 or 50amp 240v sub-panel in the spring. In the mean time, I am going to install receptacles and start insulating the walls.

The walls are 8 foot tall 2x4 frames on top of 2-1/2 foot tall concrete foundation. I have R14 rockwool insulation for the frames - is this the typical R-value for insulating walls? It was between this or R12 fiberglass. (I'm in Canada, by the way - +30C in the summer, to -30C in the winter)

My main concern though is the concrete section of the walls - will I need to do anything here, or is it "ok" to leave it exposed? Am I wasting my time insulating the rest of the wall if I don't also insulate the concrete section? If I do insulate the lower section, how do I deal with the transition?

At the front of the garage the concrete is exposed and un-sealed both inside and out. At the back of the garage it is exposed inside (shown below) and partially buried on the outside. As far as I can tell, the outside is not sealed at all where it's buried. I saw a video that talked about how the foundation should be sealed and insulated on the outside rather than the inside. Is this necessary? Should I dig out the foundation and at least seal it with something where it is buried? Obviously people insulate and seal the inside of their basement foundations; I would think this would be basically the same situation.

What would be the ideal way to insulate the concrete - foam board? Since the bottom 2-1/2 feet of the wall would then protrude from the top section, is it normal to just leave a ledge there? Money wise, it would be ideal if I could just leave the concrete section alone but I don't know if if the concrete will suck all my heat out, making all the upper insulation pointless!

Looking for all opinions, comments and suggestions, as this is my first time doing this kind of project.

Thanks!

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T Bredehoft

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That much concrete will sucks the heat out. Glue onto it the thickest piece of foam insulation you can afford. then glue onto that a piece of either plywood or partaicle board at least 12mm thick (half an inch) cap it with a piece of 2 X 4, flat, secure it to the base of the wood wall and the plywood/PB. Use the 2 X 4 as a shelf for Oil Cans, tools, rags, anything at all, or leave it to collect swarf/dust.

Edit, If you have problems with too much rain (any?), tar the inside and the floor before installing the foam board.
 

kdecelles

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I think the r 14 for 2x4 is standard . I have about 2 feet of concrete pony wall and it is uninsulated. My siding comes over the seam by an inch or so it helps mitigate drafts

I live in Alberta , is comfy in minus thirty but my walls are 2x6 and have r20

I'd leave it as is.


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RJSakowski

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Concrete has an R value of between .3 and .6 per inch. A six inch wall will give you something like R3, about what a single glazed window is.. Insulating the outside of the concrete will give you a heat reservoir in the building. nice if you intend to heat it continuously as it will help to even out temperature changes.but if you intend to heat it only while using the building, it will take longer to come to temperature. Insulating the inside will take up usable space but make heating easier if you will have times when you are not heating. The net effect on energy usage should be the same either way.

I don't believe that the moisture barrier will do much for you on a poured concrete wall. It is intended to prevent moisture ingress on subsurface walls.
Two inches of extruded polystyrene will give you an additional R10 which will bring your concrete close to the framed walls.

For a garage, the biggest source of heat loss will most likely be the door(s). Even if you insulate the panels, getting a tight seal around the door is difficult. It doesn't take much of an air leak to negate the effect of the insulation.
 

ThinWoodsman

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Pretty good points all above. I just did something similar (enclosed and insulated a concrete single-car bay in a barn that I use as a garage), so I'll add a few things that I learned.

* Wall insulation doesn't have to be that great. I used ~R-10 rockwool and it was more than sufficient, rigid foam at R-7 should be fine (I made inserts out of this for the windows and it works great). There has to be some insulation, so bare concrete is not an option on an outside wall, and there has to be some air gap for the insulation to work. This basically means you have to frame over the concrete part and add insulation (you could use construction cement to glue rigid foam board directly to the concrete, but you lose the air gap), which leads to two options: extend the existing frame using another set of 2x4s (and wood ties to atach to exisitng frame) and have very very thick walls, or frame just the concrete portion with maybe a foot over overlap onto the existing frame. As mentioned above, the second gives you a thin shelf, running the length of the wall, which can be useful if you put it at elbow level or higher. You could even build a sturdy shelf *onto* the jutting-out portion of the wall: use some 4x4s for support, mabe a workbench running that entire wall. The back support of the workbench could be integral to the wall (i.e. bolted through to the concrete), though you'd have to design it carefully so as to not break the thermal seal when banging on something in the vise. For the walls themselves, cover with plywood, OSB, underlayment, or sheetrock if you're not one of the people that's immediately turned off by the stuff.

* Ceiling insulation does the bulk of the work. Get something like R30 up there, again make sure there is an air gap between the insulation and the roof. This may mean lowering the ceiling by a foot or so.

* Build an inner set of doors. Think of it as a movable wall. I built a pair of 4' wide doors immediately inside the barn doors, which had provided no seal whatsoever. The new doors bolt into the ceiling and floor, and latch together with slide bolts for a tight fit. The doors are insulated like a wall. If you are using the garage to park a car and for a shop, build the doors to enclose the shop (gotta protect the car). If building these at the outer door, you can design them to swing inwards (and become walls) during nonwinter, or to be removable, but basically you want to think of this as something that never opens when the temperature is below freezing.

* Don't worry about the foundation. I was going back and forth on whether to do as you suggest; talked with a builder who was doing some unrelated work for me, and his opinion was that it is not worth the effort involved. It is a great thing to add in when doing new construction, as you are looking at cost of materials and maybe an extra couple of man-hours, but a retrofit is big project to do it right, and the benefits are not that great (not zero, but think of it as adding an R-value of 2 or 3 to give you some perspective). I left the foundation and the concrete floor as-is, and keep a $40 electric radiant oil heater (Peloris I think) running on low; the shop stays at 40 F and heats up to 50 fairly quickly. Next week will be the real test: so far it has only gotten down to the teens, but in a couple days we go below zero for awhile.

* Cover all seams, gaps, cracks, etc with expanding foam. This is probably less of an issue with a proper garage; I must have gone through a dozen cans of the stuff.

* Run conduit on the surface. Looks like it's too late for this one judging by your photo, but it is very nice being able to work on the electrical system without having to go into the walls.
 

Boswell

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one comment about the need for an Air Gap. There are two ways that heat will transfer out of your shop. Conduction and Radiation. Conduction is the movement of heat between things that are touching and Radiation is how heat transfers to something that is not touching (gross simplification). Stuffing Fiberglass insulation in a wall takes advantage of Conduction. There are millions of small Air-to-Fiberglass transitions that the heat has to negotiate to get from inside to outside. No Air-Gap is needed for this to work at the rated R-Value. Foam Board usually works on both the Conduction (the foam part) and by reducing Radiation. This is done with the metac Surface on one side (or both) of the foam board. For a Radiation barrier to work, you must have an Air-Gap. I have always heard that 3/4" is the minimum. You can go online and find lists of materials and how well they radiate (or don't) Short answer though is aluminum is very poor radiator of heat energy (but a great conductor of heat energy) Gold foil is even better but usually only NASA can afford this and uses it for space probes.
When building my house, in addition to the normal fiberglass insulation in the walls, I then put IR (radiant) barriers on the EAST and West facing exterior walls and the Roof. In some cases I used foam board spaced 3/4" from the studs using furring strips. In other places I used stapled heavy duty aluminum foil to the furring strips. Regardless. Insulation like Fiberglass does not need an AirGap but a radiant barrier (like foil or foiled surface of foam board) does. Ideal installations would use both Conduction barriers and Radiant barriers.

Good luck
 

WalterC

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This may have already been mentioned.
I do hvac work (45 years now) and do heat/cool gain/loss loads on structures. The biggest load is the attic/ceiling, infiltration issues (Air leaks around doors and windows etc) then windows, large doors, then the walls. In your climate of cold as heck and frozen ground- the concrete falls somewhere between one of them- we don't have that problem down here in hot as heckville.
Our minimum attic insulation is R38, but R32 is ok. Walls at R13.
 

MarkM

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Took over a year to get done but it has made my garage very comfortable. I am on the East Coast in Canada so we get our share of cold weather, yet can be quite warm in the summer. It is about a garage and a half. I Have a vehicle project in as well as my shop.
I took the fibre panels down and used pink insulation with two layers as there was enough room to keep the loft. Then a thick vapour barrier. Added a drop down door where the stairs are. Added a 220 heater with a thermostat with 3000/6000 watts. I Have done nothing to the concrete floor. My benches and stuff is made of wood which I think helps as metal is just like ice cubes.
Even when it is minus fifeen celcius out I can go there in the morning and it is hovering around zero. Half hr. Or so on low and it s up to four. In an hour I am at ten and then it gets quite comfortable.
My garage door has just been filled with rags and such to close the gaps.
It s great to be able to go do some work in the frigid months.
I ll get some pictures today. I have also added fire blankets hanging down from the ceiling to the floor to contain the heat on my shop side and for welding. Used my tech cable casing along my entrance door with foam and a cut rubber pc. On the bottom of the door.
The fire blankets make a huge difference keeping the heat in my area and cycling the hot air in that area.
 

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Tozguy

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Jester,
Re the cement I had a similar decision to make.
As already mentioned above, I would insulate the cement from the inside (really the only option). Cement conducts heat out like gangbusters. I used spray on 1.5'' of PU foam. It is insulation, seals gaps and is a vapor barrier. You can even do it yourself with the kits available. Then, depending on the type of activity inside cover with gyproc or plywood, glued in place with PU foam lines. If it creates a ledge where the wall meets the foundation use the ledge to your advantage.
I live in a similar climate and have learned not to skimp on insulation. It pays immediately in comfort and in the long run with lower heating cost.
Now is the time to do it right.
 
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MarkM

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Here Are the pics I promised. The fire blankets are also used to close off my lathe and mill when I weld or some heavy grinding. The blanket in front of the bench cuts across the bench towards the mill and a third blanket continues giving me an area to weld and not worry about the ill affect of the dust and welding. Planning an assembly slash welding table right in front of the mill on casters. The blankets help out huge with the heat cycling around me. There s an older Toyota pickup on the other side. The tech cable and foam help as well and the high tech cam door closure adding the pressure. Funny I ve been saying i ll get a proper door a few years now. Get some money and the shop takes seems to get it.
 

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pdentrem

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Not in any order as I am free thinking.
Max out the ceiling. If there space above the ceiling is open, I would spread out house wrap on top of fiberglass insulation. This will reduce the thermal cycling of the air in the insulation. Fiberglass insulation acts only as an air filter when there is air movement, the house wraps slows this down. Cover the the inside with vapor barrier and stop all air leaks. This comes from a study done a few years ago here in Canada.
Sheet the walls with what you want after vapor barrier and insulation.
Dryloc paint on the exposed concrete to reduce humidity and possible mold issues covered or not. I would cover that exposed concrete with 1” or more of foam, covered in wood.
Cover the floor with rubber matting where you can. This will keep your feet warmer!
Will the car live in there? If so use Racedeck where it will be and the rest with Drycor panels. Makes a huge difference on temps and humidity.

My shop is made of insulated structural panels for the walls that has 3 1/2” of foam sandwiched between OSB. Regular stick construction for the roof, insulation is 5” of foam and OSB interior. I covered the concrete pad with a huge one piece rubber mat that I got from a conveyor belt company. Hold back the humidity and no cold feet. I use a ceiling mounted radiant heater.
 
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