My wife insists the garage should be closed in the summer, because we run the AC inside.

However - when leaving the garage closed, temperatures reach roasting levels better suited for cooking than living. I'm thinking the heat from a closed garage will be at least as detrimental as leaving the garage open.

We live in a new house with properly insulated doors and windows.

Will leaving the door open raise the AC workload - (and thus the bill) ? And if so - is it likely to be a large, medium, or small increase (relatively)?

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    Ideally it shouldn't matter if the connection between house and garage is properly insulated. – DA01 Jul 28 '15 at 23:01
  • Thank you. I'm a little confused by the word ideally though. Given that this is a new house, would it be reasonable to expect this? – dgo Jul 28 '15 at 23:35
  • There are minimum code requirements to aim for and then there is the ideal to aim for. We hope for the latter, but the reality is that it's often the former. – DA01 Jul 29 '15 at 1:40
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    @user1167442 Most homes; even new ones, are not properly insulated and/or sealed. – Tester101 Jul 29 '15 at 1:42
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    Is there living space above the garage? How many walls are shared with the garage? Is the garage door insulated? – Tester101 Jul 29 '15 at 1:43

To the extent that it matters at all (and it shouldn't, because there are fire-resistant walls between the garage and any living spaces), the extra load on the air conditioning is proportional to the temperature of the garage and nothing else.

The heat flow from the garage into the house is proportional to the temperature difference between the two spaces, divided by the the thermal resistance of the wall(s) between them. The latter is a constant.

So if leaving the garage door open makes its temperature lower, that's what you should do.

  • I can't tell you how happy your answer makes me. – dgo Jul 30 '15 at 2:18

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