These are foil sided panels for use in home insulation. They are about 2 inches thick. I cut them to size and put them down in my existing refrigerator box, wedging them together to form tight walls. I stuffed smaller pieces into any gaps. Then I covered this with "low temp" foil tape to make a smooth continuous surface.

I suspect that over time the panels may absorb water... so I was thinking about a solution to avoid water contact, and decided that a soft sided cooler or two inside of all this would just further aid the insulation, and add baffles to contain the cold. The softsided bags are also easy to remove, hold condensation and meltwater, and are easy to clean. Costco happened to have these really large bags available for a pretty low price. About $15 for a 12 gallon bag. Shoot, if I can hold 2 sixpacks, some eggs and cheese and a mess of veggies... and maybe some frozen meat... I'm good to go.

So what I have is the original 6 cu ft box, that has 2-4 inches of expanded in place foam lining the the walls, which I covered on the inside by these foam panels, then lined with foil, with a soft side cooler further inside of that. The end result is about 4-6 inches of insulation with another 1/2 inch supplied by the soft side bag.

This is not perfect by any means... it is simply stop gap until I decide to rip out the existing box, replace all the existing foam, and then add refrigeration and reglass the whole thing. A huge messy project in my book... best suited by professionals or at least folks well skilled in working with fiberglass. I am good with electrical, plumbing and mechanical... but I am quite weak in wood and fiberglass.

In the meantime, I have a well insulated icebox. If I can get 5-6 days ice use out of it... I'll be happy. Most of my cooking really doesn't require a lot of refrigeration. So this setup might just stay this way for quite a while... if it keeps the beer cool.