Just had a couple of skylights removed and shingled over. Got tired of the leaks and worrying about hurricanes plucking them out.

I'm planning to drywall the openings shut but there's a bunch of heat radiating from the plywood and I think I'd better put some sort of insulation up there or I'd just be creating one hell of a hotbox.

I'm thinking of getting insulating foam in a can if there's such a thing and spraying the underside of the plywood.

Or, I could get some A/C duct board and cut it to fit and glue it onto the plywood foil side up, too. Don't know if that would be thick enough to do much good or even if its the best material for the job.

Any suggestions would be appreciated.

If I understand what you mean, you basically have a uninsulated box to the roof.

If that's the case why not drill a hole and add a can of mono foam

I forgot to post a picture. This is what the larger skylight opening looks like. I want to wallboard the hole shut, flush with the rest of the ceiling.

Looks are deceiving the hole is 3-1/2' deep at one end and 4' deep at the other. I don't want to fill that much cubic space with foam. I'd rather just foam the bottom side of the plywood and a bit around the edges if that would work. Maybe have the foam 4" thick or something.

What is mono foam?

Within the area that will be covered by the new drywall, cut a hole in each side wall to allow some heat to vent through the attic. Then install regular fiberglass insulation on top of the new drywall to keep any remaining heat confined.

Thanks! Sounds like a good plan. The attic is very hot - black roof in Florida - but still not as hot as that trapped air would be.

Let me ask you, though...would it still be a good idea to apply some sort of insulating material under the plywood itself. I know people who get their attics sprayed with a product called icynene (sp?) but one insulation guy said that if you spray it on the plywood it would trap moisture. Don't know if that was true or not. Just seems that stopping the heat at its source wouldn't be a bad idea.

It's a expanding spray foam insulation. Can has hose on it you point and shoot, it expands BIG time, one large can of foam will probably fill up a car.

http://www.rustoleum.com/product.asp?frm_p...d=605&SBL=5

Nice. Looks like that'd be something I could get at Ace or Lowes. Thanks for the link!

If you want something to pass inspection you can use it to fill rust holes in cars, and paint over it... not a great idea mind you but does work.

This was the same idea I came up with. Be careful with expanding foam. Spray a little at a time and let it expand before adding more. Damn near blew out three brand new windows the first time I used it

If you want insulation on the plywood, I would just by some BlueBoard insulation. Around 2 inches thick. Glue it in place. Do not use nails or you will puncture your roofing material. Spray foam from the bottom on a ,somewhat, flat surface may not stick too well.