Should I insulate my detached garage?

[Jon Bon]

I recently built a small detached garage with a room in the attic. I am playing around with the idea of insulating the garage, cost would be reasonable. My question is how much benefit do I get from adding r13 to the walls and r19 to the ceiling?  I am thinking I might put my office above the garage, in theory it would be the warmest place. Climate here can get pretty cool but not terrible. I am not looking to fully condition the space but just increase the number of usable days I could be out there if that makes sense.

Has anyone done this? Did you notice a difference? Would that difference be worth $800 bucks in insulation?



Adding a heat source in the future is possible.  Also have an insulated garage door and high quality windows and door.

[Fishindude]

Insulation is cheap and will make the building a whole lot more comfortable summer and winter.   If you ever want to heat or cool the building, you would be a fool not to insulate it.

[lthenderson]

I agree with FishinDude, insulation is cheap and easy to do. We insulate all our unconditioned farm buildings that we work in with any frequency because is just slows down the heat transfer so they don't heat up so quickly in the summer and don't cool down so quickly in the winter. It is a big YES that a little bit of insulation is noticeable in work comfort.

[Jon Bon]

I agree with FishinDude, insulation is cheap and easy to do. We insulate all our unconditioned farm buildings that we work in with any frequency because is just slows down the heat transfer so they don't heat up so quickly in the summer and don't cool down so quickly in the winter. It is a big YES that a little bit of insulation is noticeable in work comfort.

Ok PERFECT

I was hoping this would be the answer. I just want a little bit of delta from being outside. As little as 10 degrees would probably make a big difference. Also means I might be able to store paint/caulk/etc in there.

Follow up question: The baffles for venting the soffit. How far up do those need to go up? just 24 inches or so, or all the way up to the peak? I have 2x6 trusses 24' on center.

[SnackDog]

You will need to upgrade your garage door if it not already well-insulated and gap-free.

[EricEng]

Do you ever try to heat or cool the space?  If not...it should be just ambient outdoor temp even with the insulation.

[Jon Bon]

Do you ever try to heat or cool the space?  If not...it should be just ambient outdoor temp even with the insulation.

I mean thermal mass, and solar gain are real things. So is a 500 pound engine block at 500 degrees.

I am still TBD on if/how I would heat. Office is upstairs in the attic so that would be the warmest place.

[lthenderson]

I agree with FishinDude, insulation is cheap and easy to do. We insulate all our unconditioned farm buildings that we work in with any frequency because is just slows down the heat transfer so they don't heat up so quickly in the summer and don't cool down so quickly in the winter. It is a big YES that a little bit of insulation is noticeable in work comfort.

Ok PERFECT

I was hoping this would be the answer. I just want a little bit of delta from being outside. As little as 10 degrees would probably make a big difference. Also means I might be able to store paint/caulk/etc in there.

Follow up question: The baffles for venting the soffit. How far up do those need to go up? just 24 inches or so, or all the way up to the peak? I have 2x6 trusses 24' on center.

Depends greatly on type of insulation and the care of applying it. If it is bat insulation, you don't need baffles at all. If you blow it in, the baffles need to be deeper than the insulation you are applying plus a little extra so you don't carelessly fill them too.

[EricEng]

Do you ever try to heat or cool the space?  If not...it should be just ambient outdoor temp even with the insulation.

I mean thermal mass, and solar gain are real things. So is a 500 pound engine block at 500 degrees.

I am still TBD on if/how I would heat. Office is upstairs in the attic so that would be the warmest place.

The more mass and insulation just means it will lag behind the outdoor ambient cycle.  It will stay cool longer into the morning/afternoon.  It will stay warmer longer into the evening.  That can be beneficial and detrimental depending on time of year and time of day you plan to use it.

I'm just speaking from years of using insulted but unheated/cooled space overseas.  Insulation alone didn't help with the sub freezing days nor 110+ days.  During summer took longer too cool off after the sun dropped, and stayed cold longer into the morning during winter.  Now if you are going to have a unit to heat or cool, then go for it.

[Jon Bon]

Yeah that makes sense.

I was not expecting shorts and t-shirt in the living room or anything, but maybe more like a 3 season room? Id take that if I can turn on a space heater to take the chill off when I am working in there or window AC in the summer. But for the most part just moderates the temp a little bit.

[Jon Bon]

Depends greatly on type of insulation and the care of applying it. If it is bat insulation, you don't need baffles at all. If you blow it in, the baffles need to be deeper than the insulation you are applying plus a little extra so you don't carelessly fill them too.

Yes I was going with bat insulation, probably paper faced as it is easy to find. The standard r-19 stuff 24 on center rafter bays.

I should specify, the bat insulation will be going into the rafter bays themselves as this is a room in the attic trusses. So the insulation will be going up against the underside of the roof.

[EricEng]

Id take that if I can turn on a space heater to take the chill off when I am working in there or window AC in the summer. But for the most part just moderates the temp a little bit.

Then yes, that will work well. 

[nburns]

I have been thinking of doing this myself as well.  Just purchased a home that has a 20'x20' detached garage and want to use the space as my shop but temps here in New England are dropping fast and make it no fun to work.  I have been contemplating R-13 for the walls and R-19 for the attic crawl space above.  Overall, I think it will definitely be worth the cost in the long run.

[Jon Bon]

I have been thinking of doing this myself as well.  Just purchased a home that has a 20'x20' detached garage and want to use the space as my shop but temps here in New England are dropping fast and make it no fun to work.  I have been contemplating R-13 for the walls and R-19 for the attic crawl space above.  Overall, I think it will definitely be worth the cost in the long run.

Well you do it first and report back here!

I am probably thinking in 2019.

[coffeefueled]

Posting to follow. We have a detached garage we want to use as a gym, but east coast winters are cold. We'd like to get it to 60 degrees in the winter with a space heater. Anyone have thoughts on rigid foam board insulation vs bat for the walls? So after insulation are you adding vapor barrier on the inside?

[bacchi]

Posting to follow. We have a detached garage we want to use as a gym, but east coast winters are cold. We'd like to get it to 60 degrees in the winter with a space heater. Anyone have thoughts on rigid foam board insulation vs bat for the walls? So after insulation are you adding vapor barrier on the inside?

Rigid foam works but it's a pita to install in the stud cavities. You'd have to seal it in place, closing all the gaps, with spray foam. It's a lot of work but can be done.

[robartsd]

The more mass and insulation just means it will lag behind the outdoor ambient cycle.  It will stay cool longer into the morning/afternoon.  It will stay warmer longer into the evening.  That can be beneficial and detrimental depending on time of year and time of day you plan to use it.

I'm just speaking from years of using insulted but unheated/cooled space overseas.  Insulation alone didn't help with the sub freezing days nor 110+ days.  During summer took longer too cool off after the sun dropped, and stayed cold longer into the morning during winter.  Now if you are going to have a unit to heat or cool, then go for it.

A fan pulling in outside air at the time of day that is the nicest can greatly help an insulated space be comfortable for several hours following. Well insulated, high thermal mass can work quite well if your climate provides wide daily temperature swings.

[Fishindude]

I'd seriously consider getting a heating / cooling system for that garage after you get it insulated.   A little thru wall electric unit would work fine and you'll find yourself using that space quite a bit if it's comfortable.   A woodstove for heat is a nice option too if you have the space and there are no issues with your insurance company.

[Jon Bon]

I'd seriously consider getting a heating / cooling system for that garage after you get it insulated.   A little thru wall electric unit would work fine and you'll find yourself using that space quite a bit if it's comfortable.   A woodstove for heat is a nice option too if you have the space and there are no issues with your insurance company.

For sure, that would be step 2.

Would you recommend conditioning the space 24/7 or just as needed? I am considering running a gas line out there, and getting a small gas heater. Or would you just just get a small electric space heater? I can't imagine it would cost very much to heat if it was A. Well insulated, and B. Kept at about 50 degrees. I would probably also have a wall unit AC if I was working upstairs, but use that only a few days a year.

https://www.homedepot.com/p/Dyna-Glo-30000-BTU-Natural-Gas-Infrared-Vent-Free-Thermostatic-Wall-Heater-IRSS30NGT-2N/303388497

[Fishindude]

Gas heat is cheaper than electric heat typically, so a small forced air gas furnace would heat it cheaper than the thru wall electric I first suggested.  However you have the cost of running a gas line. plus the cost of buying and installing two units that you wouldn't have with a thru wall combo unit.

I'm in the midwest and keep my garage at the lowest setting, approx. 40-45F, which is plenty warm for vehicles, etc.   If I'm doing a project out there, I crank it up accordingly.   Anytime you open a garage door, you lose a lot of the heat or cool in a hurry and your unit will run a bit recovering, so you need to get in the habit of getting in and out with your vehicles quickly and not leaving the overhead door open very long.

[lthenderson]

Would you recommend conditioning the space 24/7 or just as needed?

That depends a lot on what you are doing out in your garage. For working on vehicles with wrenches and other metal objects all having lots of thermal mass, I like to leave the heat on for quite awhile before I go out there to work. For stuff like woodworking, cranking on the heat an hour before heading out is plenty of time. Like I mentioned above, I have an air register from my central heat plumbed out to my garage (no return for obvious reasons) and it keeps my garage in the low to mid 40's during the worst of winter which is just enough to de-snow and de-ice the cars overnight. This is the first house I've owned like that and I can tell you I will never own another house without that feature.