How would you insulate this 2 car detached garage?
Hey hope everyone is doing well. I have a 2 car detached garage that needs some restoring. It’s about 20×24 no insulation or finished wall. Open rafters and cathedral ceiling. From my understanding no ventilation. I would like to create an attic space for storage. Also use it as a garage gym, workshop, man cave. Plan to use radiant heating as it is not living space, only need to heat in winter for short periods of time. Is it worth insulating at all? Here is what I’m thinking.
1. professionally spray foam the whole garage, not sure cost as I have never done this before.
2. Fiberglass insulation batts in wall and ceiling, drywall it, create attic space, leave space under roof alone.
3. Fiberglass batts in walls, ceiling drywall, use rigid foam under roof sheathing instead of insulating attic floor.
Is insulating the attic floor going to be more costly than insulating under the roof sheathing, would rigid foam work in this situation. I saw a video online about a radiant barrier? Basically taking rigid foam and just attaching on to the rafters instead of squeezing it in between. My concern with fiberglass batts is it will be nesting for rodents critters as the garage is detached and in winter won’t be spending as much time in there. I attached some pictures.
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Replies
Should you insulate or not depends on how often and for how long you will be heating the space. If you are going to keep it at 68° all winter long that is one thing. I you are going to heat the space for 30 minutes a day for the week after new year’s that is another.
Radiant heat is only a good idea if you would be opening the overhead door often and likely to lose the heated air when you did.
Putting the insulation at the roof line is an expensive option and best avoided if possible. It looks like a pretty steep roof so the roof will have about 30% more surface area than the ceiling. That means you need 30% more stuff to cover it. Putting the insulation on sloped surface pretty much forces you to use foam that is way more expensive. If you must insulate at the roof line pick one of these options.
https://www.greenbuildingadvisor.com/article/five-cathedral-ceilings-that-work
If you are not sure how much you will use the space I say install a wood stove. You will get lots if exercise cutting, splitting, stacking the wood and a little more feeding it into the stove. The wood will likely be free and make enough heat the you will not need any insulation.
Does the storage area really need to be conditioned? If not insulate between the new ceiling joists with cheap fluffy stuff.
If you are only going to heat the place occasionally, I like the idea of an oversized gas furnace with a remote control so you push a button and 15 minutes later the place is toasty warm.
Walta
Thanks for your help. I have a hot dawg propane heater that was given to me, not sure if it works or how to install but I can look it up. I would like a more finished look, might as well insulate new ceiling with cheap fiberglass and leave the attic unconditioned for storage. You are right in that the roof would be more cost for not much more benefit. I also like the wood stove idea, although it would not be free as I’m not anywhere near a wooded area.
How do you feel about propane? Honestly never like using gas, I prefer electric or wood burning but I already have the propane heater. With insulation how big of an electric unit would I need to heat the area quick? Is gas just more efficient?
If I don’t have soffit vents, I basically have an unvented roof. Any potential issues with insulating the ceiling below?
Also what would happen if I only insulated only the walls and put an attic floor but didn’t insulate the ceiling? Just curious because that would be less expensive and easier to do. I’m assuming I would loose a ton of heat but for me it would be a much smaller and less expensive project to complete. Wouldn’t have to worry as much about ventilation issues or condensation with roof.
I will disagree with Walta. Having a modicum of insulation in a garage, with attendant air sealing, increases the utility of that space enormously. My own garage is rather haphazardly insulated at R13 overall with insulated doors, and it will neither drop to the lows outside nor rise to the highs. There is a huge difference working in a space that rarely falls below the low 40s and does not rise above the low 80s. Tools are no longer ice cold. Objects are not coved in a haze of rust.
Ok maybe a dumb question, instead of filling the ceiling with fluffy insulation, could I simply lay an insulated floor? Rigid foam with plywood on top, or some kind of pre insulated boards? I would have the attic floor to store light items. I have had a piece of leftover rigid foam in the garage for years untouched but I left a small piece of insulated duct work and mice had a fiesta. Of course the insulation value would be lower but seems like less work for me and easily removable if an issue arises.
Foam us usually more expensive than fluff. I see nothing wrong with your idea. Rigid foam has the potential to make air sealing easier
The hot dawg propane heater would be unvented and will put like 8 pounds of water in the air for every gallon of fuel burned and you will be breathing the byproducts of combustion like carbon monoxide. This requires you to keep a window or door open for ventilation. Too much ventilation and you have no heat too little and you take a permanent nap.
In general propane is the most expensive fuel in any market.
Electric resistance heat would likely require 240 volts and 30 amps that is unlikely to be present.
My garage is insulated but unheated I think it is always warmer in the garage than outside in the winter that is nice in the summer it is not so nice.
Walta