Grass roots trailer insulation

I have a 24' enclosed race trailer with a metal roof skin that is basically laid over thin cross section u channels that make up the box structure.

I'd like to insulate the roof and possibly the floor - on the cheap.

I was thinking that spray in foam insulation for house construction might work well, but it appears to be quite expensive. Also, not sure if it would outgas enough to be a problem in an enclosed space.

Anybody tackle this type of project already? Anybody know what they use in RV's and can it be purchased "retail"

Thanks, Neil

My 6x12 had a decent amount of space between the top skin and the crossbeams. As a result, it sounded like a big kettle drum when it was windy with the skin banging against the crossbeams. At the track, I just jammed some folded cardboard up there to quiet down the noise.

When I got home, I hit my local home repair and bought a 4x8 sheet of hard insulating foam. Worked great and helped to also push back some heat because it was lined with foil on one side.

-Rob

Carpet underpad?

It's light, too.