There is a pretty large detached garage on my property (built ca 1995) approx 16' x 29'. Previous owner had started putting R-11 insulation on the walls and underside of roof, but I think may want to take a different approach. Am looking for suggestions.

My goal would be to put in some sort of heating (Northwest Ohio) so that I can use this for woodworking throughout the year. My question is aimed at construction and insulation.

See attached photos. He put fiberglass insulation directly against the underside of the roof. I'm not sure this is good practice, especially if a ceiling is installed.

The roof appears to have a 2x4 ridge and rafters, and 2x6 joists--all spaced 16"oc. There's also an L-beam made of 2x6s (I don't know what this is) that run the length of the shed with vertical posts attached every 4'.

Will this construction hold an OSB ceiling + insulation? Any other suggestions on ceilings?

If I put in a ceiling, should I remove the insulation that's against the roof?

The soffits are vented but there are no other vents on the roof or attic area. Should vent/s be installed?

The garage is on a concrete slab.

Thanks for any advice or suggestions!

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  • The wiring needs help, at least from a fastening standpoint. Be sure you know the rules (or consult someone who does).
    – isherwood
    Commented May 16, 2023 at 19:55
  • 5
    Northwest Ohio? Please - don't get cheap-to-buy but crippling-to-run electric space heaters. Do get one of the modern, extended range (cold climate) heat pumps for heating - traditional American makers are very "behind the times" sadly... Japanese and Korean units win. Some are DIY (you need a vacuum gage set, but you install and test your piping with nitrogen and don't need to handle refrigerants). You'll thank me in July... boy howdy! Because heat pumps also A/C. Commented May 16, 2023 at 21:26
  • Yes! Have been looking into these. Was thinking I could get by without the AC but perhaps I'll change my tune in a month or so. :^)
    – Krewldad
    Commented May 22, 2023 at 17:39

1 Answer 1


Assuming budget is not "Sky's the limit":

Delete rafter insulation (but carefully), add ridge vent and/or a functional cupola, reuse rafter insulation (see "carefully") in wall cavities, consider foam sheet over studs before plywood or drywall sheathing for additional insulation and to break the stud heat leak. Then cast an eye at the garage door - I have a "commercial" insulated one that manages R-17 and consider it well worth the price I paid for it. An uninsulated one is a gigantic heat leak.

Don't see a lot of point in an OSB ceiling. Heavy and not good in a fire. Cheap and functional (and lightweight) seems to be white formed steel (steel roofing used as a ceiling material - white helps with light distribution and you don't have to paint it.) it's also nicely fire resistant, without the weight of drywall for that. Cellulose loose fill over that.

If you insulate well, a good cold climate mini-split will give you heat and cooling (and a washable electrostatic dust filter) and compete with or beat fuel based heating prices, without the ignition source and venting requirements of a fuel based heat source. That will beat resistance electric heat by a factor 3-4 and the air conditioning comes for free (but you don't have to use it if you don't want to.) It can also be a dehumidifier, which can be useful for a wood shop some times of year.

You might want to dig down and insulate around the slab edges, since I assume it wasn't insulated around or under as built. You might get a pleasant surprise and find that it was insulated, but I doubt it.

  • I agree on all points, though I don't love white steel. It gets pretty gunky after a few years. I have a mocha color on my garage ceiling and like it very well. It doesn't show cobwebs or sawdust.
    – isherwood
    Commented May 16, 2023 at 19:53
  • You can dust mop it with a long pole mop handle. My view on white for shop spaces is that it's a shop space, so I don't care if it shows dirt, and it makes a huge difference in the lighting of the space so I can DO work. I use white floor paint, too - gigantic difference .vs. gray concrete in light level - finding small parts that have fallen to the floor is somewhat easier too. Yes, it gets marked up - I choose a floor paint system where recoating it is not a bother, or a huge expense.
    – Ecnerwal
    Commented May 16, 2023 at 20:02
  • Fair. There's a difference between a garage that gets used as a workshop and a true workshop. My ceiling is so cluttered with suspended crap that I would not want to mop it, and most of the reflective quality would be wasted anyway.
    – isherwood
    Commented May 16, 2023 at 20:04
  • OSB lining on the walls is great for hanging things, but that also leads to mess. I like pegboard near the bench, but plain walls elsewhere. Space above ceiling joists can be good for storage but access for long things can be a challenge.
    – Criggie
    Commented May 17, 2023 at 5:32
  • All great comments! Thank you! Steel ceiling never even occurred to me. I was considering a mini-split. My only concern would be the time it takes to heat from ~30 degrees to something comfortable. Was considering supplementing with an electric utility heater...perhaps I'm over thinking this. First order is cleaning it out and getting an electrician for upgrade and to figure out how far previous owner got.
    – Krewldad
    Commented May 22, 2023 at 17:33

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