Can windows in garage doors affect the temperature inside?

11 years ago

We are building a home in Central CT with a 3-car attached garage. Assuming that the house is insulated properly, do windows in the garage doors make it less insulated? The master bath is above the garage and I don't want it to be cold in the winter. The doors face the south.

Featured Answer

renovator8

11 years ago

Glass lights in a garage door would not "allow more cold air into the garage"; it would be the perimeter of the door that would allow that.

What the glass lights will do is allow heat to leave the garage and whether that is substantially more than what a blank door panel would allow depends on the R-value of the of the blank door panels and the U value of the glass.

Since we don't know any of that information we can't respond to your question. However, if the garage is not mechanically heated, it would effectively be heated by the interior spaces adjacent to it and above it. That means the bathroom above will be giving up heat to the garage as fast as the floor/ceiling insulation will allow. the heating system in the bathroom would be designed to replace that lost heat. the fact that the heat loss is at the floor makes that considerably more difficult but not impossible.

You should seal the bottom of the floor with as much spray foam insulation as you can afford and not worry about the door glass; it's the least of your heat loss problems.

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Comments (12)

renovator8
11 years ago
It depends on the garage design. The additional heat loss through the glass will be proportional to the area of the glass, insulated door panels, and the exterior walls, the R value of those elements, the temperature to which you intend to heat the garage, and the amount and kind of insulation you put in the ceiling.

The issue will be the cost of heating the garage enough to keep the bathroom floor warm and avoid pipes freezing. You might want to put electric heating mats under the bathroom tile.

The ceiling insulation should be spray foam in order to seal it from cold air leaks and avoid CO poisoning to the occupants above if a car is left running below.
graywings123
11 years ago
Just an opinion: an unheated garage will be cold in winter with or without windows, and the windows would have minimal effect on the temperature. I would rather walk into a garage with some natural light. Heating the bathroom floor is the way to go.
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brickeyee
11 years ago
Insulate it well and put in enough south facing widows and it might even get warm.
renovator8
11 years ago
The windows are of little importance; it is whether or not you plan to heat the garage that will make a difference.
mcfromct
Original Author
11 years ago
Thanks everyone. We have no plans to heat the garage. I am more concerned with the temp of the rooms above it and was wondering if garage windows make a significant difference as far as allowing more cold air into the garage and therefore making the rooms above it colder. Sounds like they don't make a huge difference and we should focus on making sure the ceiling in the garage is insulated properly and possibly putting heated floors in the bathroom. Thank you all for your input!
worthy
11 years ago
we should focus on making sure the ceiling in the garage is insulated properly

There is only one truly effective way to do it. Here's Mike Holmes using my sub.
mcfromct
Original Author
11 years ago
Renovator8- I could really use your expertise in looking at our plans. They are in pdf format. Is there any way I could send them to you without posting them to the whole forum?
renovator8
11 years ago
You can reach me via gmail.
mcfromct
Original Author
11 years ago
Thank you so much-
mcfromct
Original Author
11 years ago
Just sent it, Renovator8. Hopefully the file isn't too large.
crazy_in_mason
11 years ago
My builder had a unique solution to this problem. He constructed an area immediately below my bathroom. It was maybe 3 feet deep. He insulated the exterior walls with insulation. He then gave the area its own vent to and from the Hvac. My bathroom floor is never cold in the morning.