Yes, just in case your spouse makes you sleep in it.

I live in PA. I am assuming the outside walls are block. It isn't necessary to insulate the outside walls. We have lived in homes with and without. Our present garage's outside wall is uninsulated and the coldest the garage has ever been is in the 40s.

I am curious what "block" means when referring to outside walls. Normally I would think some thing like concrete block but almost no one builds a house out of that any more.

I am also amazed that "in the 40s" you mention as seemingly just fine for you!

There are things that really matter because not all garages are the same. First, is there a room that is conditioned above the garage? Second, is the garage attached to the house by 1 wall or 2 or more? Will you have a well insulated garage door?

Then there are characteristics of you that matter - do you work in the garage - projects/car repair etc? Do you find "in the 40s" acceptable?

Your vehicle will always appreciate something closer to 70 degrees and I know I appreciate getting into a 70 degree car. Basic R-13 insulation is pretty cheap and in combo with an insulated garage door will keep the garage warmer. Not 70 of course in the dead of winter but perhaps warmer than 40's - but it will really matter the characteristics of the house around it.

I have a 1 wall attached, nothing above garage that I insulated both attic and walls. Not same as house but something. I think my door is R-11 or close. Typical cold winter morning temps are 55 when 25 out. . It was my first garage that was so minimally attached which is one of the reasons I insulated - I didn't want to go out to a really cold car.

With a more integrated garage, insulation can help with indoor heating costs and temperature issue if there is a room above.

We live in northern NJ and we only have the inside garage walls insulated. A few years ago we had our garage door replaced with a high quality door with high insulation ( as hubby works on cars and maintains our generator, snow plow, and lawn mower in the garage) and it never gets below 40 degrees.

@David Cary our garage has 3 walls facing the house. We added a long storage area that runs the entire length of the house. Above the garage is our master bedroom. We occasionally do work in the garage but mostly would just like a warmer car in the winters and my biggest concern is making the entire house more efficient. If insulating the garage will help with this, we will do it. As for the garage door, would it be made with the insulation already part of the door or is this something that is added to it?

David, yes concrete block. In PA it is common for the garage to be in the foundation. Foundations also can be poured concrete. 40s is the lowest the garage has got on the coldest day. Normally it stays in the 50s on typical winter days. Your not going to have a garage at 70 in the winter even with insulation without a alternative heat supply. It depends if you want to pay additional utility costs for that heat.

Insulating all the garage will help keep it warmer, but remember every time you open the garage door you are letting in all the cold air anyway. Good insulation between the house and garage is imperative.

So OP presumably doesn't have block as a wall because he mentions R-13 which is standard 2x4 stud wall fiberglass bats. You would not do that to block.

Here in NC, we don't use block for tall walls ever like a garage. Maybe for a 5 foot crawlspace but basements are poured generally. I am always fascinated by regional differences in building practice. Big piece of concrete is of course helping to keep your garage warm. So the wall material is absolutely relevant.

So, obviously you don't "need" to insulate garage exterior walls. But it is really cheap and will help a small amount with garage warmth and house energy use. Of course, the garage interior walls will be well insulated - because code requires it.

Given that you only have 1 exterior wall and presumably much of that wall is a door, do you really have any wall to insulate? Because of wind issues, our garage walls near the door are often stud packed so little room for insulation. Often called a shear wall.

Your door is bought insulated, not added later. I seem to remember a $200 upcharge for what I did. Standard is still insulated (generally) but you can pay to up the R value. I seem to remember R-3 standard, R-11 and R-16 available.

Hylo33, what is the outside walls constructed of. That does make a difference.

I would insulate the garage.

Insulation is cheap. I would definitely insulate the exterior walls.

Absolutely insulate them while you have a chance. In fact, as this is one item builders usually let homeowners do since it doesn't affect schedule or mess with anything else, put batt insulation in walls around the bathrooms and between bedroom walls for some sound attenuation. It can all be accomplished in the quiet weekend prior to the drywallers coming. Insulation is in fact very cheap and you should only be a couple hundred dollars in depending on size of house.

@3onthetree what type do you recommend for inside walls for sound?

I would go ahead and insulate the garage to help retain heat in the garage, and retain heat in the home as well. But there are a couple caveats:

• If you don't have insulated garage doors, you may still lose most of your heat through the garage door. Insulating that one wall around the door isn't going to have much impact without an insulated door.
• Your garage may stay warmer and retain more of the heat lost from the house with insulation, but it will not be anywhere near as warm as the house itself without being heated. Don't expect that your garage will stay 70 on it's own in the middle of winter.

I guess this is the difference between living in a more temperate place like NC and where I've lived in Michigan and northern Illinois and Indiana, but 40s is plenty warm for a garage in the winter, when it might only be a high of 20-30 outside in the middle of the day and considerably colder at night. And where we have lived it has required a garage heater to maintain that temperature. Your cars won't sustain any damage at that temperature, especially compared with the third of the time they spend parked in a lot or open garage while you are at work.

@3onthetree thanks for the advice. We did all the exterior garage walls today. Our GC asked us to hold off on soundproofing insulation until they insulate the rest of the house and have it inspected. Do we need to do just the walls that face high noise areas? Or do you have to do all 4 walls?

Many folks in the NE with bedrooms above the garage speak of how cold it is. Not sure if he is insulating the ceiling between the garage and bedroom, but you might want to consider this in addition to putting the bedroom on it's own zone.

Code requires insulating ceiling between garage and conditioned space. The problem lies in that insulation is not magic so you can still have temperature issues even with good insulation. It certainly helps a bit if the garage is 50 instead of 40.