I was just at an energy-saving home show and came across a product I am thinking of using...

Somehow my garage (once a carport) was lined in plywood (not sure if it was legal at time of construction) - the walls have been lined with drywall, well and good, but the ceiling still is plywood. I had to cut some access holes into the ceiling to rectify some plumbing issues and plan to leave some manholes in there so I will have future access. It transpires that there was no moisture/air barrier put in, and the insulation has mostly dropped out of the ceiling joists and rests on the top of the ceiling material

This product I am interested in is a foam-core material with a foil backing, and a white finished side which is paintable. It would be easy to fix it in such a way that I could remove it in the future or just build said manholes.

I had already figured I would have to take the whole ceiling down and probably get spray-on foam insulation done, as I believe the spray stuff works as an air/moisture barrier. The master bedroom is above the garage and needless the say the floor is cold in winter, and I would like to remove the carpet for a wood floor. In its present state that would make it a lot worse....on the upside, nothing in the garage freezes in winter! (door is an insulated double skin type)

So, does anybody have any thoughts or concerns or experience with the stuff? I was thinking of using the 1' material which is claimed to have an R27 rating, impressive for the thickness. If I go with spray on, I am going to have an awkward situation ensuring the plumbing found up there remains on the warm side of the envelope, I am going to have to build a complex box around it, probably with styrofoam insulation as there is only an inch or so clearance to the false ceiling below.

If I use this stuff, I can go right over the existing ceiling. I can leave the old insulation in there (although I suppose the existing insulation would be more effective if it was back up between the joists, but I don't really have an option to get it back up there) Insulating it on the surface would be great in that the whole space would end up on the warm side of the house, being better and simpler for the plumbing.

My concerns? Fire, and mechanical damage, it is coated/covered but will be easy to damage. I suppose I could drywall over it if I used long screws...not sure how effective that would be but would be an option. Big attraction is leaving everything else alone.

Cost is around CDN$ 1.41 psf or around $45 per 4x8 sheet which should be at least federal sales tax-free, as an energy-saving product. According to the literature it's a class-a product according to the fire rating test, I don't understand the rating system too well but understand it's better than some material, not as good as drywall itself, but would appear to satisfy the legal requirements for the most part (I will see what I can dredge up on my local codes)

Any thoughts? URL for company is below:

Here is a link that might be useful: P2000 Insulation systems