Insulate my detached garage

[fguillozet]

I live in Ohio and recently bought a home with a 24x28 detached garage. Right now it is bare bones. Open ceiling, stud walls. I am interested in making it into a workshop/mancave and don't know the best way to insulate. I'd like to leave the open ceiling to store some bigger items but will put a ceiling up if thats my only option. I plan to heat it with a propane heater only when I'm out there. My original plan was bat insulation in the roof but I hear that can cause some roting to the roof? Or can I use a foam board in the roof to keep enough heat it? I plan to do the walls with roll insulation with paper backing and eventually use OSB board overtop. Any suggestions would be great.

 

[90limited]

it would help to know how the garage is built... stick built or framed for drywall with studs and joists 16" on center...

 

[J-man67]

Your detached sounds a lot like mine. I have roll insulation in the walls, covered with osb. That was there when we bought our home last year. Not sure how much it helps. Only found out it was insulated after putting my truck hitch through the back wall! Oops! Anyway, I too have thought about closing off the ceiling, but I prefer to have the extra storage space as I feel I am already running out of space. I use a little propane heater when I'm out there. Gets warm relatively quick and will stay warm for about 30 mins after I turn the heater off. Added a nice detector out there so I don't kill myself while heating and all has been well. When I add on, or knock this one down to go larger, that's when I will worry more about efficiency and such. For now just enjoy it!

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[jkrswld]

My previous garage was the same. I ended up putting the 3 or 4 inch rolls into the walls, kraft faced, and closed up with OSB. Then i used the same rolls in the rafters and closed the topside with OSB to support me for storage up there. Bottom remained exposed and I sold it that way. I heated with propane just while I was out there, but just have walls + ceiling like that helped out quite a bit. I don't think it froze a bottle of water I left out on the inside that winter, though if I recall correctly the beer fridge still seemed confused. Made it so much nicer to ramp up the heat with the loud torpedo heater and then have it actually hold that heat for a while so I could turn the heater off.

 

[J-man67]

That sounds like a good option. Insulate and close off the roof rather then put up a ceiling. No, not the most efficient, but a lot better then nothing. Might go this route.

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[rburke65]

You will lose the majority of your heat through the ceiling. Insulate the ceiling, and do the OSB in the attic like the previous two posters said. Watch you don't over load your ceiling/attic area if it has not been designed for storage!

 

[Hoat]

its more expensive than roll insulation but I would consider spray insulation. My dad just had it done to his house that is under construction and it makes a hell of a difference over Kraft face.

 

[Alexbn921]

You will lose the majority of your heat through the ceiling. Insulate the ceiling, and do the OSB in the attic like the previous two posters said. Watch you don't over load your ceiling/attic area if it has not been designed for storage!

+1
Do the ceiling first. Also don't forget the door. Make sure the seal is good and add some kind of insulation if there isn't any.

 

[bczygan]

As you have mentioned, you have 2 choices with the ceiling. Either install ceiling joists and put insulation above them, or put insulation at the rafter area.

First, welcome to GJ.

Second, you need R38 ceiling insulation at least. That is 12" of batt. This would mean no storage at the ceiling because the insulation would be much taller than the ceiling joists.

So the next choice is putting it up at the rafters. You need to keep a 1" space below the roof deck, for the entire length of every rafter space for ventilation. And you need to tie the ventilation of these rafter spaces together at the top with either a continuous ridge vent or multiple roof vents. The only exception is if you use spray in foam insulation. Frankly, this is the best insulation. But you still need it to be thick enough to get the required R value.
Instead of spray in foam, you could use rigid foam panels. You still need the 1" ventilation space. And you would need enough depth to get R38. Depending on rafter size depth and R value of the foam, you might need to build it up to below the depth of the rafters.

Your choice.