Insulating my garage

[whynot]

My garage has power but no heat, so I'm just starting to look into the best ways to insulate, within a budget of time and money. (Then there's heat, too. I've been reading the Garage Journal Forum for ideas.)

Anyway:
Detached 2-car CBS, hip roof, 20x20 slab, overhead door, two windows, one walk-in door.
The overhead door is 20 years old but in great shape, steel with a foam core. Could use some tightening up on the sides.
*[Door details edit: installed 1994, Wayne Dalton "Foamcore 37" galvanized steel w foamed-in-place poly core R 5.62]*
The walk-in door is steel in good shape, pretty well sealed.
The windows are old wood sash, might get Harvey windows like we have on the house.

Before I get too far on my ideas and what I've done so far, I first want to ask, has anyone worked with Roxul Comfortbatt?
http://diywithroxul.com/en-us/comfort-batt.html

I had this in mind for insulating between the roof rafters (24" spacing). Would probably need to set up scaffolding and deal with all the "stuff" and bikes that are in the garage.

Thanks,

Kurt

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[GearHd6]

I've got one of these http://www.dornbackfurnace.com/pdfs/unitheaters.pdf to heat my garage and I love it. My garage sounds about the same as yours. 20'x20' 2 story (2nd story not heated) with an old non-insulated wooden garage door and I have 3 windows. It can be 30 degrees IN the garage and it heats to 50 degrees in about 15 minutes. Installation is pretty simple, you can vent out the roof or it can power vent out a side wall which is how I have it. There is only 1" clearance between the heater and the ceiling so height isn't a major issue. I've got it set up so it's above my roll-away toolbox.

I bat insulated my garage. R13 in the walls (2x4 construction) and I believe R18 in the ceiling. It works well for me. It's been just over 3 years since I had my propane tank filled. I don't heat the garage full time, only when I'm out there working.

I'll add that my ceiling is only 8'. If you're open up to the roof rafters your heat results may be different than mine.

[TheIglu]

Do you have any joists?

If you insulate in between rafters, you'll need to vent under the insulation. Be a lot easier/smarter/more efficient to insulate at the joist level and leave the rafters uninsulated.

R16 isn't much for the top of a building. I run R38 in my ceiling, that's the lowest I'd recommend. So cheap to insulate with fiberglass, may as well do it as much as you can the first time.

You can get an R15 in batt form for 2x4 walls now. I'd go with that.

[GearHd6]

I agree, get the max you can for 2x4 walls. I insulated mine about 6 years ago and R15 wasn't around then.

And like Clayton said, insulate to the joists. There is no point in insulating all the way to the roof line and wasting that heat if you don't need that much height.

[whynot]

Thanks. I'll have to take a closer look at the joists, may require moving some wiring. Agree, a lot more efficient to put in a ceiling and insulate that rather than insulate the roof. I'd have to move the "stuff" that's stored on top of the joists, a good idea to get rid of some of it anyway.

At present, the walls are plain cement block. I'm doing one wall at a time, point, caulk, paint. Wasn't planning on furring strips and sheet rock or anything like that on the walls.

For the floor, I'm considering a couple of rolls (9x20) of this:
http://www.autobarn.net/garfloorprot.html

I know I should be planning heat at the same time. There is gas piped to the house, but to get it 30' of so to the garage would take excavation (tearing up the landscaping) and permits. (Thinking out loud.)

(I'll post some pics, probably tomorrow.)

[TheIglu]

Wiring can stay in place in most cases. Just slice the insulation (NOT the paper), tuck wiring into the notch. It'll still insulate just as well.

For the walls, run some 2x4's. Then you can run wiring in the walls and insulate properly. Make sure you vapor barrier on the back side of the wall with sheet plastic.

[whynot]

OK, for joists, there are three 2x3s running front-to-back, and one 2x4 side-to side. Just about all the wiring runs on the sides or the bottom of the joists, with a couple of short runs on top, easy to move. The overhead door motor has a platform built over it (?) for support, that would have to be reworked. And there are four 2x4s connecting the joists to the rafters to support the door motor. Then I could build a ceiling and insulate it.



So far, my plan is, make a plan and a budget over the winter, then come spring, empty the garage and do everything ... rapidly.

[TheIglu]

That's not going to be easy. You don't have really any joists to speak of. Adding them will be a major PITA. I'd consider a hanging drop style ceiling for cheap cost and ease of install.

[GearHd6]

Yeah that looks tough. Being an open span with no center beam you really have nowhere to hang joists off. You'd be stuck building a similar truss system like your door opener hangs off.

The roof isn't really that high so you could almost get away with insulating that but there again you'd have to ventilate it with ridge vents, soffit vents along with those plastic rafter vents.

[whynot]

... for cheap cost and ease of install.

Sounds good to me, thanks.

[GearHd6]

Copied and pasted from a car forum. Sounds like the way to go for you.

Had a dropped ceiling in one of my previous garages, and it worked great! It had the fiberglass 2X4 drop in panels, and added 6" batt insulation on top. Never any sag or issues, and allowed easy access for the storage area above in the attic.

I had that garage for 14 years (built new in 73, and moved out in 87). Had both heat and a/c in a 24X25 garage, with a separate 25X8 storage shed attached in the back (access through a door in the rear wall of the garage). The drop in ceiling did a great job of sealing off and insulating that garage during the cold and hot Chicago weather.

[TheIglu]

Damn, I'm on a roll.

[whynot]

Thanks, Jeff, Clayton, the plan starts to take shape ... .

Kurt

PS -- spell check: make that "insulating" not "unsulating" (Where did I get that?)

[R7]

If it were me, I'd use the 2x4 R15 batts in the rafters and hold it all in place with R10 2" rigid over the entire area, fastened to the roof rafters. If there's no ridge venting (doesn't look like it with the hip roof), then adding the venting space between the insulation and roof will do nothing, so that's a step you can skip. If you had a steep roof, I'd toss around the idea of a drop ceiling, but with that low roof, you'll gain very little. Plus a ceiling fan tucked up as high as you can will spread the heat around evenly

As for the block walls, that's where you're going to lose your heat. I'd do the same thing with the 2" rigid insulation on the walls

[Intrepidse17]

How crazy do you want to go here? Are you going to keep it heated 24/7 or just when you are working out there?

Realistically some r15 between the rafter bays is the cheapest and easiest route. Spray foam is more expensive, but you get better r value.

If you really wanted to install a ceiling of some kind I would go a foot or two up from the top of the wall plate and run 2x6's from rafter to rafter, no need for a beam this way and no fighting to get a 20' length into place, also no worry about wiring or the garage door opener. Then stuff r30 between the joists. For the remaining bit of sloped 2x4 ceiling, grab more 2x6's and tack them onto the 2x4's to make a faux 2x10 and put more r30 into there.

Realistically though, wide r15 batts in the roof is most likely the best because it is cost effective and involves the least construction but still allows you to keep some heat in. It's probably not worth much more effort unless you planned to do the whole garage so you could keep it heated 24/7. Those concrete block walls are probably like r3, that massive door is probably r10ish at best so why bother going all out on a ceiling when you are losing a lot of heat everywhere else.

[whynot]

Thanks, guys, that sounds good, too, had a fan in mind if I go that route of bats between the rafters. And for the walls, 2" rigid instead of a stud wall on top of the block, I like that.

This won't be living space, but work space where heating to 50 would work, 60 max. and only when I'm in there, and I wouldn't bother in extreme cold. It can get awful hot in the summer, maybe a window unit A/C ... thinking out loud ...

[Stromper]

That roof is tough

Foam spray isn't cheap but it will follow the shape and give a decent R value

Gas is and will be cheapest heat plus you could look at radiant which heats things and you NOT the air and works fast

You can buy blankets for the Garage door insulation vinyl backing to prevent air through the cracks

Cement Blocks are terrible insulators , you need walls or insulated exteriors

[RandyO]

Cement Blocks are terrible insulators , you need walls or insulated exteriors

concrete is terrible insulator but excellent thermal mass, put insulation on outside of building, once heated, concrete will continue to radiate heat and don't loose precious floor space inside. any exterior rigid foam insulation will need to be covered so that it is protected from ultraviolet light

at minimum, put radiant barrier on the interior walls

[whynot]

The ideas just keep comin'! Thanks to all. I read about radiant barrier on the Garage Journal Forum. Garage door insulation sounds good. It might come down to time and money, how much I will do myself, how much I would hire someone to do, how much aggravation I want. So I've started writing up my plan with options and links.

[TheIglu]

If there's no ridge venting (doesn't look like it with the hip roof), then adding the venting space between the insulation and roof will do nothing, so that's a step you can skip.

Won't the cold roof hit the warm insulation causing condensation inside the structure, regardless of presence of outside air through soffit and ridge vents?

[R7]

Won't the cold roof hit the warm insulation causing condensation inside the structure, regardless of presence of outside air through soffit and ridge vents?

It will condensate with or without the venting. The venting keeps the air moving to constantly dry the condensation, without the flow of air, the space between the structure and the insulation becomes useless. Do you space the insulation in your walls away from the structure? No, same theory.

[TheIglu]

Makes sense.

[Stromper]

That pyramid roof design does not look like it could provide enough peak venting for soffit/air channels.

Perhaps rigid foam boards sealed with tape over the rafters. This would provide an insulating ceiling and an air gap so you could put venting even perhaps power or solar power vents near the peak. This would make it even cooler in the summer. Shiny aluminum facing would be tacky but really add light to the garage

[whynot]

Perhaps rigid foam boards sealed with tape over the rafters. This would provide an insulating ceiling and an air gap so you could put venting even perhaps power or solar power vents near the peak. This would make it even cooler in the summer. Shiny aluminum facing would be tacky but really add light to the garage

That sounds simple and effective, thanks.

I've been looking at "Reflectix" radiant barrier products and applications, lots of good info at http://www.reflectixinc.com/

[RandyO]

That pyramid roof design does not look like it could provide enough peak venting for soffit/air channels.

the "pyramid" roof design is probably the most efficient for venting, a cupola top center works best