Insulating my attached garage.

[Pervsrodshop]

Been a member for a couple of years and have found lots of good advise but now that I want to insulate my garage I cannot find all of my answers. So I live in MN and I do NOT plan to keep the garage heated all winter just heated when I am out there working on my project truck. So that being said I will do R13 in the walls with 1/2" sheet rock, and was thinking about just doing R19 in the ceiling with 5/8" sheet rock. So a little back ground on the garage, when the PO had the house built instead of sheetrocking the while ceiling he had them do about 6ft out from the house then up to the ceiling to create a little attic area. Then with the remaining rock he (as I see it) randomly hung it on the walls. @ sheets on one side, and 4-5 sheets on the other side of the garage. So NONE of the wall sheets have insulation behind them. I took 1 sheet down already and 1 sheet has a built in cabinet on it and there is not insulation there either. So the other 4-5 sheets do NOT have insulation behind them. So for those sheets do I
1. leave them alone and do nothing?
2. Take them down and insulate and replace them?
Or 3.... Other option?
So when insulating my walls do I have to use vapor barrier or is the Kraft facing enough?
Then for the ceiling do I have to use vapor barrier there or is the facing enough. fyi I am leaving the little attic area intact. I plan on using R19 for the ceiling since I just want to help keep the heat in to take the chill out of the air in the winter. Then also foe the ceiling do I need to run the "air flow channels" under the insulation or can I just lay it right on the rock? And yes my soffits are vented on both sides of my garage. The PO had stuffed insulation over them to keep the cold out. I will be removing all that. I just want to be able to use the garage more in the winter and summer. I was fine working out in the garage in the winter running a 240v heater while wearing long underwear before but have saved some money to do this. So I am NOT looking to make all the seams and all perfect I just want a usable, comfortable garage to work on cars in year round. So any tips or advice would be GREAT! I am also adding more lights and fans. Thanks in advance.

 

[xtremek]

You just opened a can of worms. I'd insulate. I'm told the Kraft facing is enough for a vapor barrier. Lay the insulation right on the rock, but like you said, make sure you have a clear path from the soffet vents to the ridge/roof vent. I'd tape the joints. The tighter you can make the garage, the better.

 

[Pervsrodshop]

Xtremek - Thanks that was kinda what I was looking for straight to the point. I was just going to lay the insulation up to the edge of the garage wall so the soffit is open, then obviously above the insulation will all be open. So the air can all flow up there. As for the joints my bro in-law just used 2" pin strips and painted them white with that walls and it looks good without all the work of mud, tape, and sanding.

 

[DC73]

Insulate the entire envelope - all wall cavities and the entire ceiling. If that involves taking down sheetrock, best to bite the bullet and do it. R19 is not recommended for ceiling insulation in your climate. It's better than nothing but you need more and it's never cheaper to do than when you first do it. I think the recommended amount for ceilings in Minnesota is R49 for the southern half of the state and R60 for the northern. Put at least R30 but do as much as you can afford up to the recommended levels. It will be much cheaper to heat the space with adequate levels. Put as much as you can in the walls without compressing batts if you go that route.

Research vapor barriers on GreenBuildingAdvisor.com and BuildingScience.com. There is a Q&A forum on GBA where experts hang out that can give you good info.

DC

 

[xtremek]

Xtremek - Thanks that was kinda what I was looking for straight to the point. I was just going to lay the insulation up to the edge of the garage wall so the soffit is open, then obviously above the insulation will all be open. So the air can all flow up there. As for the joints my bro in-law just used 2" pin strips and painted them white with that walls and it looks good without all the work of mud, tape, and sanding.

You should still have either a ridge vent or gable vents, soffits are not enough.

 

[CNGsaves]

I'd try for R19 in walls and R38 or more in ceiling since you're in MN. Cheap route to go for ceiling would be blown-in cellulose, even if you put it over top of bat insulation that is there already. Just remember to have covers so your soffets still breathe cool air up to roof venting (ie whirly bird or passive turtle vents). R50 for ceiling insulation should be your target.

+1 to finish out all the sheetrock joints with proper tape/mud so you truly get "envelope" as airtight as you can. Also use spray foam cans to seal any cracks or holes. Good luck.

 

[nadogail]

IMHO, just take a clue from the Nike ad and Just do something, even if it is wrong. Wrong insulation is better than no insulation, just quit planning (sometimes the same as stalling) and get to work on that project thing.

 

[UpNorther]

Re: Kraft insulation vapor barrier.
I also live in MN, used to be an residential insulator years back. Yes, the kraft insulation is considered a vapor barrier. If you were to put poly over it, that would be a double vapor barrier, creating condensation between layers. With that being said, the best way would be to hang regular unfaced insulation batts, then poly over it. It is a far better vapor barrier than kraft faced alone.

 

[Richard Cranium]

insulate as much as you can. The more and better insulation the better you will be.

 

[LARRY Z]

If you can do spray foam - do it. The companies that do it are slow in the spring and can give a good price. We did a friends shop / garage and then covered the walls with 1/2 plywood. Made the walls a lot more useful.

The cost vs pay back is worth it. It will also help cut down on noise - usually a big plus..

Just be sure to run all the electric before you have it sprayed.