[HawkinsGuy]

Is insulating the garage doors an effective method to lower the temperature in the garage? We have thought about installing an attic fan as well but the boss is a bit concerned about poking a hole in the roof and is also wondering if hurricane force winds will dislodge the fan and will leak. We’ve also thought about adding insulation above the garage to help. I’ve seen the thermal roof barrier too. Does that “cook” the roof shingles by redirecting the heat back into the shingles?

[PJOHNS2654]

I added insulation above the garage (there was none there) and insulation panels to garage door. The garage temperature now is 6 to 8 degrees different than air conditioned or heated house.

[MrFlorida]

I added Styrofoam panels to the metal garage door which faces south, the garage is cooler than it was without the panels by a few degrees.

[retiredguy123]

In my opinion, insulating any unconditioned space will not provide much benefit. Insulation will only slow down the heat transfer process. But, unless the garage space is conditioned, the inside and outside temperatures will eventually reach a state of temperature equilibrium. That is why builders never insulate unconditioned spaces.

[GpaVader]

My experience is that it does help, but it won't lower it, it helps keep it from heating up more. I have an East facing metal door with windows. I use my garage building models and painting them so I have to control both the temperature and the humidity in that space. I started this winter by doing the insulated panels in the doors and it does make a difference, as an earlier poster mentioned about 6-8* different. Later I tinted the windows in the garage. Finally, this past week I added a split AC so I should be ready for the summer heat. In theory anyway... regarding the solar attic fans, I use the attic for storage and while I am not sure it will do much to cool the space it will move more air and help to moderate the space. I have other experienced neighbors that don't use their attic for storage but instead put a screen where the cover used to be to help promote airflow. I put a ladder in my space.

[Boffin]

Front of house faces south. Reflectix installed in garage doors as well as passive vents; high on one side low on the other. Reflectix also installed on rafters above garage. In my case, effective.

[Topspinmo]

Originally Posted by PJOHNS2654

I added insulation above the garage (there was none there) and insulation panels to garage door. The garage temperature now is 6 to 8 degrees different than air conditioned or heated house.

Probably not on the sunny side???

[Toymeister]

Radiant barrier, thermal barrier as the OP calls it (Reflectix brand name) can help on a garage situation, however, when used over the entire home yields limited results. Specifically, you will save 1.5 to 1.8% of your electric bill during the cooling months.

Attic fans, which have already been confused with solar fans, are generally a waste of money. Solar fans, at 900.00, only run at the claimed CFM rating at solar noon and stop working before the attic has cooled. Often this is at 11pm to 2am. You are far better off simply adding additional inexpensive static roof vents.

The vents do extend the roof life, however, the actual replacement schedule will be an economic one. Home owners insurance increases dramatically once the roof is ten years old.

If the OP wants scientific evidence to support my claims, just ask me.

[MartinSE]

I think @Toymeister said it best. I will add to answer the OPs question, it is NOT necessary to poke a hole in the roof to add attic ventilation. Our garage fan blows it's garage hot air into the attic which then exhausts through the venting along the edges of the roof and a couple long vents at the crown.

We had Solar Guys (?) put in a garage fan and insulate the garage door. They did an excellent job, and a reasonable price. It works. But, it does not get the garage COOL. It keeps it from getting unbearably hot. If it is in the high 90's outside and a bright sun shiny day, the garage will still get close to 90.

My BIG concern, that I did not think of at the time, if the garage fan creates a vacuum in the garage, which you can feel when you open the door into the house. I am concerned that when it is running, that low pressure is pulling some of the house AC cooled air out. I am probably going to put a few more vents on the garage door in an attempt to reduce the low pressure.

[retiredguy123]

Originally Posted by MartinSE

I think @Toymeister said it best. I will add to answer the OPs question, it is NOT necessary to poke a hole in the roof to add attic ventilation. Our garage fan blows it's garage hot air into the attic which then exhausts through the venting along the edges of the roof and a couple long vents at the crown.

We had Solar Guys (?) put in a garage fan and insulate the garage door. They did an excellent job, and a reasonable price. It works. But, it does not get the garage COOL. It keeps it from getting unbearably hot. If it is in the high 90's outside and a bright sun shiny day, the garage will still get close to 90.

My BIG concern, that I did not think of at the time, if the garage fan creates a vacuum in the garage, which you can feel when you open the door into the house. I am concerned that when it is running, that low pressure is pulling some of the house AC cooled air out. I am probably going to put a few more vents on the garage door in an attempt to reduce the low pressure.

I would reconsider adding more holes in your garage door. The guy next door installed a fan and vents in the garage door and turned to whole thing off within a month. You just don't get enough air flow through those small garage door vents, and they compromise the strength of the door.

[MartinSE]

Originally Posted by retiredguy123

I would reconsider adding more holes in your garage door. The guy next door installed a fan and vents in the garage door and turned to whole thing off within a month. You just don't get enough air flow through those small garage door vents, and they compromise the strength of the door.

Thank you, I would not have thought of that.

I usually open the garage door 4 to 6 inches in the summer, so the exhaust fan can move more air. But, I hate to do that at night, since I don't want rats or squirrels getting to my car, last time squirrels got to my car it cost almost $3k to repair the wires - LOL!

[thevillages2013]

Originally Posted by PJOHNS2654

I added insulation above the garage (there was none there) and insulation panels to garage door. The garage temperature now is 6 to 8 degrees different than air conditioned or heated house.

That totally depends on what temperature you keep your thermostat set to. If you keep it at 78-80 I can see that (maybe) but if your a/c is set to 72 there is no way

[tophcfa]

Save the money on insulation and put it towards an overhead screen door for the garage and use that instead of your garage door during the hotter months. We love ours, plus it goes up and down much quieter and quicker that the garage door and we can see out but passers by can’t see in : )

[tsmall22204]

Add a screen door to your garage. It will stay cool and have air flow. I also put a small fan in the window. Works great

[bobeaston]

I have a workshop in my garage and am OK with working there with temps that match outside air, without the beating sun. The east facing dark brown doors used to do a fantastic job of heating the garage far beyond outside temps every morning. ...until...

I also have all 3 solutions mentioned here, door insulation, attic fan and screens.

1. The garage door insulation (radiant barrier reflective foil) virtually stopped the pizza oven effect of sun on dark brown heating. That alone kept the garage from heating up beyond outside air temp. BTW, I kept a set of measurements of surface tempos before and after and could show inside surface temps up to 145 degrees. No longer.

2. My fan installation did not include cutting vents in the door since my garage has a window that I can open to act as the vent. The fan is good for a little bit of air movement. I don't use it much since "little bit" are the operative words and that's not much of a cooling effect. What's more, in the evening or early morning, the fan draws in the ambient 100% humidity as well. For me, it's not worth the money.

3. I also have roll down screens over both garage doors. These are THE BEST part of my solutions because they, and the open window, open the garage up to flowing air driven by ever present breezes in our neighborhood. These alone keep the temp a few degrees below outside air temp.

No, not a lot cooler than outside temp, but a LOT cooler than the radiant power of sun on dark brown doors.