I am (finally) wrapping up the complete
rebuild of my
refrigerator and
freezer. I used Cryogel Z from Pacor Inc. to get the maximum R-value in the thinnest layers I could.
The Cryogel Z is made for insulating very cold pipes, rooms, etc. It has an R-value of about 10 per inch. So 4" would give R-40 which is good for a low temp
freezer in the tropics with a good
compressor. The excess I have left over is 10mm thick. You cut it to fit.
I have an 18' continuous roll, 58" wide, which is 87 sq. ft. I bought 60 linear feet, which is 290 sq. ft. and didn't need the remainder. I paid $5.40 per square foot and would sell what I have left over for $3/sq. ft. for the whole 18' roll, which would be $260, plus
shipping.
I also used a couple of vacuum insulated
panels custom built by R-Parts for one wall but could not use it for most of it. The VIP's are far higher R-value per inch but wouldn't
work with the existing framing I had to
work around. One inch = R-40. But they have a long (for me 4 months) lead time, as they are made to order by a separate manufacturer. It is also extremely delicate and cannot be pricked or bent. One screw and it loses its vacuum and is then not as good as even foamboard.
It is not toxic (per the manufacturer) but is dusty and the dust is kind of sticky. You need to wear gloves and a dust mask to handle. I used shears from Home Depot to cut it. There are videos on the pacorinc.com website as to how to handle and install it.