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What is the best way to reduce heat gain in South facing garages?

pshyvers | Posted in Energy Efficiency and Durability on

This forum has had a lot to say about how foil bubble radiant heat barriers are silly and a waste of money.

I’m interested in reducing the heat gain in my South facing garages from the intense high desert sun. My garage bakes, and my neighbors is quite cool and comfortable, for a garage. I know he has done attic ventilation above the garage, and installed a radiant heat barriers on the door.

I am inclined to follow his footsteps. But is there a better choice for the door? Heat retention in winter would be nice, suggesting foam board, but I can’t imagine I can get a good air seal around the door, and foil faced foam hardly allows much of an air space for radiant blocking.

If I should use foam, how thick? 2″ seems a bit heavy and bulky.

I don’t need perfect, and I don’t need R-18 like a proper insulated garage door, I just don’t want an oven, and the heat gain from the direct sun is immense.

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  1. brad_rh | | #1

    We need a little more info on what you have, is there glass in the doors? Insulation in the walls? Location? In the summer most of your solar heat gain is going to be through the roof, so attic insulation would be the most bang for you buck. If you could add an overhang or awning of some sort on the S side you could eliminate most of the solar gain there.

  2. Expert Member
    Dana Dorsett | | #2

    The roof orientation, roofing type & color, the garage door & wall color, insulation levels etc all factor into the peak temperatures the garage will see. White vinyl insulated garage doors aren't particularly bulky or heavy, and will reject & retain heat a lot better than a 3/4" plywood garage door with RB paint on the interior, and a pigmented house paint on the exterior.

  3. pshyvers | | #3

    Brad, I know the walls shared with the conditioned space of the house are insulated. Not sure about the exterior walls. We are in Colorado. There are rooms over about half of the garage, which are fully insulated & comfortable, so the "garage attic" space is only over about half of the garage. It's probably not insulated though. Your suggestion of an awning is interesting- I had already been thinking of adding a mini-awning to grow vines, just because I find that attractive. If that can eliminate the solar heat gain on the door, that's a nice bonus. I'll have to work out the sun angles during the hottest months of the year to see how far it would need to protrude.

    Would installing solar panels on the uninsulated garage attic effectively eliminate the solar gain, in another two-for-one? We've got panels in the plan, but haven't decided where they should sit.

    Dana, now that you mention pigment, I notice my door is olive while the neighbor with the cool garage is tan. The door itself is some kind of wood product, seems like some kind of OSB.

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