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I am an amateur woodworker and am having a new home built. My part-time workshop will be in the garage. Where I live (central Maryland), the winters are often cold (below freezing) and occasionally much colder (+10F/-10C and below). My current home has no insulation in the garage walls or attic, so I use an electric space heater, which is almost useless when it's really cold. I am considering having the garage in the new home insulated, since it will be much easier to do before the drywall is up.

The builder is using R-20 for the exterior walls of the living spaces, but I don't need it to be insulated enough so that I can live there, I just don't want my fingers to freeze off! I am still planning on using the space heater. The entire house will have Tyvek housewrap, including the garage (whether I choose to insulate it or not).

My question is: what level of insulation should I request? The builder wants to know what level of insulation I want before they give me a quote on the price (and I can determine if it's worth it). Do I also need to have the garage door and attic insulated to see any benefit, or can I just get by with the walls? (The walls are the critical part, since I can easily add insulation to the attic and door after the fact).

A secondary question would be: is it worth it at all? One possible answer is to do nothing and just wait for warmer weather -- it's a hobby, not a profession.

UPDATE: I've asked the builder for the pricing for R-15 in the walls (can't do R-20, since the garage is framed with 2x4s, not 2x6s) and blown insulation in the attic. Still waiting to hear back from them.

UPDATE 2: The builder has quoted me over US$1400 to insulate it. Yeah, that's only $100/year, but I think I'll just wear an extra sweater, because it's not worth that much to me.

  • Is the garage attached to the house? – DMoore Feb 5 '16 at 22:01
  • @DMoore yes, it's attached to the house. There will be R-20 in the wall between the garage and the house. – Mike Harris Feb 5 '16 at 22:05
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    If it will also be your shop, consult with your electrician about increasing the number and placement of outlets and individual circuits befor the insulation goes up. – mikes Feb 5 '16 at 23:04
  • @mikes Yes indeed, that was all taken care of before construction even started :-) – Mike Harris Feb 6 '16 at 0:06
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    Yes, insulate it the same as your house...after all, as a workshop, it'll be 'habitable' space. Also consider a garage heater/furnace or a heatpump (as opposed to just using electric space heaters). Actually, I'd strongly suggest the heat pump so you can run A/C in summer while in the shop. – DA01 Feb 6 '16 at 0:18
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I would insulate it unless the cost is exorbitant.

As you have discovered, it is basically impossible to heat an uninsulated structure with just a little space heater.

Also if you are going to be keeping cars in the garage as well, having an insulated garage will keep it warmer even if you don't heat it. My garage is insulated but unheated and it is usually a good 10 or 20 ºF warmer than outside temps in the winter. The difference between a car that is 20 ºF and one that is 40 ºF in the morning is considerable.

Mine also stays very cool in the summer, so I think the insulation will help you there, not hurt you. (I bet insulating the roof/attic probably makes the biggest difference there.)

  • Well, it looks like the cost is exorbitant (or at least excessive), in my opinion at least. See "Update 2" to the question. – Mike Harris Feb 16 '16 at 16:30
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I would insulate it. Insulation is a thermal barrier; it impedes the transfer of thermal energy from one side of the insulation to the other. This means if it is warmer inside the garage than outside the house, insulation will keep it warmer longer because heat will escape more slowly due to the insulation. If it is cooler inside the garage than it is outside, insulation will keep it cooler longer because heat from outside will infiltrate the garage more slowly.

Just insulating the walls won't make your garage an icebox in the summer, but nobody here is suggesting that, right? ;-)

As the other current answer suggests, a car stored in an insulated garage will be noticeably warmer than the same car in an uninsulated garage, both because more of the thermal energy released from the cooling car will remain inside the insulated garage overnight, and because what little heat escapes from the wall of the living area into the garage will also be retained longer.

Also, if you open the window in your garage overnight in the summer, then close it in the morning, the garage will remain cooler longer into the day because of the insulation. I really don't see any downside unless it's just off-the-charts expensive.

On the other hand, insulating a garage isn't a requirement for the garage to serve its primary function of keeping your cars, tools and off-season picnic gear dry. ;-)

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    But insulation can help to reduce condensation, so the "dry" part can be affected by it. Also DO get an insulated garage door - well worth it. I have a "commercial" door in my shop - R17, metal skins both sides with foam in the middle, and a far better quality door than any "residential" I've met, for not a lot more money. – Ecnerwal Feb 7 '16 at 3:25
  • Yes, that's true, regarding condensation! There you go, insulate, and look into an insulated garage door. – Craig Feb 7 '16 at 10:20
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Insulation will help a bit to keep it warmer. A lot warmer if your garage door is insulated too.

On the flip side, it will be a warmer in the summer as the insulation will keep heat in then too. The garage to house should be insulated plus the garage to attic... which means you are talking about insulating 2 walls at most (one could be attached to house too). This is $50 in material and $50 in labor (insulation will be up with a stapler in 10 mins - cost more time to buy it). Not sure if that is what you are being quoted but it is kind of obvious if you want to work in your garage in the winter its probably worth doing for $100.

  • Comments are not for extended discussion; this conversation has been moved to chat. – Niall C. Feb 8 '16 at 18:48
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We have insulation on our garage as well as heating and cooling. For us, it was a very good decision because we have a large garage that provides a large quantity of relatively climate controlled storage and we don't have a basement, so it was great, particularly because we are in upstate NY where it can get sub-zero at night.

Even unheated/cooled, it is going to provide extra insulation for that side of the house from the outside since it will act as a buffer space. You also have the impact on the wear and tear on the car and battery from having someplace to warm up and avoid the coldest times of night.

Is it worth $1400, that's really up to you. In the grand scheme of a house, $1400 isn't much, but it also depends on how much space you need and how big the garage is and how cold it gets where you are.

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