We did a good deal of research on the different methods to insulate our cargo trailer. After spending time considering the different options, we decided to take a different approach from anything we saw that others have done for insulation.
Out initial first choice was ridged spray foam insulation. We obtained an estimate for about $1,000. There were two problems with this. The first was that the only firm in Tucson that does this work could not guarantee that they could keep the insulation to 1 inch to match the depth of the metal studs. I just did not feel up to sawing off any excess. The second issue is that the workers needed to wear hazmat suits when doing the instillation.
This gave us a concern about what fumes might linger in the cargo trailer, and it was not keeping with our desire to have an eco-friendly build.
Then we took a look at board insulation. I imagined the amount of waste that this would involve, and all of the time and mess to cut it down to the sizes we needed. We never considered using rolls of fiberglass insulation- thought there were too many problems with this.
Then Mellody came across "Mineral Wool High Temperature Insulation". This is advertised as being rigid, water repellent, sound dampening, excellent thermal resistance, noncorrosive, and chemically inert with an R factor of 4. Although not as high of an R rating as the spray foam, it come in at half the cost.
I think the instillation was much easier than the other methods we considered, and provided greater benefits. The link below shows where we sourced the insulation [no, they did not sponsor this video, and we paid full price for the product.
Grainger supply: bit.ly/2Zf0pa1