How much energy does keeping the garage door open in the winter waste?

Question

I have an inconsiderate roommate who likes to use the garage door instead of front door and he leaves it open for long periods of time as well. I'd like to know how much our heating bill is affected with the door open all the time (its low 40s now in my area). I also would like to know how much energy is used by opening and closing it approx. 15 times a day.

Answer 1

In my house it makes a serrious difference.  I live in Idaho, high mountain desert area.  It's snowing here right now, about 20 degrees outside.

Our garage door is the kind the rolls up, not the kind that are a solid door that opens upwards.  The rolling upwards at least does not create a whosh of the warmer garage air out.

Our garage is attached to our livingroom, and kitchen.  Our home is EXTREMELY well insulated.  The back of the garage is attached to a VERY large sunroom.  The sunroom has solar gain during the day, and heats up.  This in turn provides some heat, and extra wind insulation for our garage.

If we leave the garage door open too long, or the wind is blowing from the North (directly into our garage), it will make the gas stove in the livingroom kick on.  As I stated, we have an extremely well insulated house.

I don't think opening and closing the garage door is as much of a problem, as long as it is opened, and then CLOSED.  Leaving it open does cut down on the extra insualtion all that trapped air would provide, since it's probably a few degrees warmer than the outside temperature.  

We solved this problem at our house, by installing one of those keypads outside the garage door.  Now it's easy for people to open or close the door, without a remote from the car.

~Garnet

Homesteading/Farming over 20 years

Answer 2

First consider the last question, opening and closing it repeatedly. That won't waste much energy, since air can't store much energy, so letting a garage full of air out doesn't let too many kiloJoules out.

While air can't store much energy, given time it can carry large amounts. Keep this in mind...

The first question is tougher. It depends on your insulation. Does the garage get warm in the winter if you leave the door closed? If so, then it probably isn't well insulated from the rest of the home, and you could lose ten to fifty dollars a month out the garage by leaving it open for long periods.

If the garage is close to the outside temperature, even when the door is closed for hours, then it is probably well insulated from the house, and you should worry a bit less. Still, you could probably buy a pizza each month, if not a fancy meal, for what you are now giving to the utility.

Remember, it takes 15 seconds to open the garage door, walk in/out, and close it. There are 240 15-second blocks in an hour, so leaving it open for an hour is much more significant than 15 seconds.