Why is the garage so hot in the summer?

Monday, July 9, 2018

The heated and cooled areas of house, which are also called “conditioned living space” or simply “living area,” are required to be insulated to meet the Florida Energy Code standards. Because the garage, along with any open or screened porches, are not conditioned living space, they are not required to have any insulation. It is not unusual for an attic to reach temperatures of 130º F and higher on the hot afternoons of summer, and the lack of any ceiling insulation means that the heat radiates down through the garage ceiling all afternoon and into the evening.

    Some home builders insulate garage ceilings, often as option for an extra charge, and it definitely makes the space more comfortable—especially if your laundry equipment is in the garage. Since most garages have an attic access hatch in the ceiling, you can easily check to see if lack of insulation is the reason for your unbearably hot garage.

    Roll fiberglass insulation is available at the big-box home improvement stores and simple to install. Just be sure to read and follow the manufacturer’s instructions for handling the material, and leave a gap at the roof overhang to allow natural air flow from the soffit vents to the roof vents for passive attic ventilation. Unfortunately, wall insulation is not so easy to retrofit, but the addition of only ceiling insulation will make a noticeable temperature difference. 

    One of the problems we often observe with our infrared camera in homes that have had a garage or porch remodeled into conditioned living space is the lack of wall insulation, because it is impossible to add without opening up the wall cavity. The defect will cause the remodeled rooms to be more expensive to heat and cool. There will also be a discernible temperature difference in the room near the exterior walls.

    Also, see our blog post What are the common problems when a homeowner converts a garage to conditioned living space, such as a family room?

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Here’s links to a collection of our other blog posts about INSULATION: 

What are the common problems with attic insulation?

Why is vermiculite attic insulation a problem for both buyers and sellers of a home? 

How can I tell if a house has insulation? 

Why is spray foam used for attic insulation?

Should I wrap the water heater with an insulation blanket? 

Should I put some more insulation in the attic?

• What does the "R-Value" of home insulation mean? 

• Is pipe insulation flammable?

    Visit our INSULATION page for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles. 

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