The attic space over my 2-car garage was used for storage and is covered with plywood. We just permanently removed all the contents from the attic. There's no insulation under the plywood. I've insulated the garage door and tinted the door windows, but the garage still gets extremely hot in the summer and pretty cold in the winter. The rest of the attic was re-insulated a few years ago with blown in insulation and the house itself is comfortable.
What would give the best bang for the money: 1. Install Radiant Barrier to that section only. 2. Blow in insulation over the plywood. or 3. Cover that space with rolled insulation. Thanks all.

I had the same situation with my garage.

I watched CL for some free insulation and was given rolls of batting out of a warehouse where they went to spray foam.

It was plastic on one side and insulation on the other. I just cut it where it would fit between the studs and put the plywood back down.

Man, the thought of working with that plywood in a fairly tight spot already has my knees and back aching. I think the dummies nailed the stuff down instead of using screws! Did you see and feel a noticeable difference in your garage?

No on the radiant barrier unlesz thr garage attic is segregated from house attic.

I would probably roll insulation and install an exaust fan in ceiling to exaust garage heat attic during hot months.

I common occurrence in insulated unclimate contolled space is preventing heat build up.

Without climate control, once the space gets hot, the space stays hot until fall. I have had several customers which added garages and had them foam insulated. Winters are great, July and August, garage temps hover in the high 90s, even with door open several hours a day.

Watching this thread closely as I am in the same boat. I want to go with spray foam in the whole attic, but its up to $2.00-$2.50+/SF, while blowing in more insulation would run about $1.00/SF. if we go spray foam. we would have to pull/vacuum out all the old insulation, too

It was an instant change in temps in my garage. I had already added a vent on the roof and have the vents around the eves. Any time you have the attic access open (I leave it open in the warm months) you feel the air flowing even when standing under it.

Perfect, I'll do something to it this winter. Appreciate that info. Wonder if I could just use the roll insulation on top of the plywood?

I’m going to guess your walls in your garage are not insulated. That would be what I would check 1st.

You said you insulated your garage after you moved the plywood. All you did was insulate the rest of the house from the garage it sound like which is a wise move.

Step 1 check wall insulation. If it’s not insulated you can pay a company to come in make a hole between each set of studs and blow in insulation.

Next thing I’d do is get an insulated garage door. If it’s a typical builder grade it’s non insulated.

I wouldn’t want to lose the storage space over the garage so I would be pulling the plywood up and putting insulation under it. You may not think you need that space now but you likely will want it someday.

House was built in 82. Did they insulate garage walls in those days? I only added the door insulation and used a sun tint on the windows. Makes sense that the outside brick on both sides is absorbing heat and transferring it inside. Sewar Rat - Pulling the plywood and insulating under is probably my best bet as is checking those walls. I have some thinking to do!

I just went to Lowe’s and bought bunch of bags of spraying fiber and lit it up until I had 10-12in. Don’t do cellulose though it’s nasty

Can holes be cut in the plywood to allow a foam to be injected.

My garage door is insulated

If the ceiling is sheetrock, I would cut a 24" strip out of the middle (cross ways to the rafters). Then blow fiber insulation in the void between the plywood and sheetrock. Patch up the sheetrock and call it a day. Same deal for the uninsulated wall.

If the walls aren't insulated (which they probably aren't) then adding it in the attic isn't going to make much of a difference.