I've come across some 2 foot by 4 foot squares of Asphalt Impregnated Blue Foamboard from an old flat roof. It is two inches thick of foam with about 1/4 inch or more of asphalt on it and the panels lock together. I am into conserving energy and would like to put this material to work.

What building applications can I use it for? Do any of my ideas resonate with other forum members? Your input is greatly appreciated.

1. Attach to exterior walls (Asphalt side out and foam side "in" against house wrap) for an added R-10
2. Drill channels through foam parallel and touching the Asphalt layer, run pex through and use as radiant floor heating panels.

I think these might work. Does anyone see any drawbacks to doubling the panels up to get r-20 on an exterior wall (asphalt,foam,asphalt,foam,housewrap,osb)?

I already put on the roof metal, otherwise would have set these in between the deck and the metal to accomplish an unvented roof.

Thanks a lot.

The asphalt may not be a problem, but if it is, you can make a wood fence and a hot wire to trim it off.

That's a good idea. Can you explain what you mean by fence or is my sense of humor lacking.

I see what you mean, found a nice DIY device.

Yes, I meant the type of fence on a saw - a guide to keep the cut depth constant.