ISOCAST R Polyisocyanurate Insulation

[janders]

XPS (extruded polystyrene) is the blue or pink board insulation you find in Home Depot and handles moisture much better than polyisocyanurate. Beaded polystyrene - white beaded foam boards that I always think of as styrofoam - is a different animal and I don't believe it handles moisture nearly as well.

For my fridge insulation, I used polyiso on a vertical wall where I had limited room but the rest of the insulation was done in XPS. The polyiso boards come wrapped in a foil. After cutting and fitting, I sealed off all the edges with foil tape to keep moisture out of the foam. I would especially do the bottom of the fridge in XPS if you have any chance of condensation seeping down into the insulation or into the fridge cabinet from some other source.

[janders]

Here's a better description of the insulation I used on our fridge project:

s/v hello world: fridge insulation

[Patrick_DeepPlaya]

My friend on s/v Hello World used some of this in his project and he found it MUCH harder to work with, it is very crumbly and sealing the edges was time consuming. He use one layer of it on the outside of several layers of the more common blue foam board.

I'm not sure he'd recommend it...

-p

[janders]

Originally Posted by Patrick_DeepPlaya

My friend on s/v Hello World used some of this in his project and he found it MUCH harder to work with, it is very crumbly and sealing the edges was time consuming. He use one layer of it on the outside of several layers of the more common blue foam board.

I'm not sure he'd recommend it...

-p

What he said.

[skipmac]

Summary,

Unless you go with vacuum panels or some new, expensive, space age polymers, polystyrene is acknowledged as the best option. The isocyanurates have a higher initial R value but will absorb moisture over time and lose that advantage and more. This was the recommendation directly from Dow tech support and they offer both options.

[SV Demeter]

Thanks all. Makes sense now. Im guessing that the recommended R-value for a fridge is 30 meaning that I should be looking for 6 inches of polystyrene foam.