Insulating living quarters

So this spring I bought a featherlite 3 horse gn with the dressing room. I have been playing with the idea of trying to turn the dress into a living area (minus water...) My BFs dad is going to wire it so I can have a fridge and microwave and another light (as well as a couple other plugins for other things). He wires utility trailers for a living so he knows what he is doing.

But I have been trying to figure out what I should use for insulation. I want to keep it as light as possible. What would be the best to use?

Do you think spray foam would work well? My BF works at a company that makes sprayers and employees can rent the equipment- other then it being a mess putting it in it does anyone know any drawbacks of it? or what did you use?

This is an old thread but I hope I can help.

I had the spray in stuff put in and I LOVE it. Its tight and quiet, it keeps the cool out and the hot in.