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Refrigerator Insulation? Answered

I was looking at Costco and they have their big semi-rugged totes on sale this time of year for like $6!

The thing I'm pondering is sticking one in inside another and filling the space between with insulation.  But what to put in between?
You're probably thinking what I'm thinking, Pinky:  Spray it full of Great Stuff foam.

But then I'm looking at my fridge going... that thing is literally freezing inside and not even cool to the touch on the outside!  What kind of insulation do they use?  I'm guessing something trickier than Great Stuff, what with Energy Star ratings and all. 

In short: 
What is it and where can I get some!??


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Jack A Lopez
Jack A Lopez

3 years ago

As far as I know, the insulation used in freezers, and chilly boxes (aka "coolers") is not expensive or exotic, nor hard to find.

If you live in the FUS, the big box hardware mongers like Lowes(r) and HomeDepot(r), they sell solid sheets of various kinds of solid polymer foams,


like expanded polystyrene (a.k.a styrofoam) and also expanded isocyanurate (which I think is some kind of expanded polyurethane).

Actually it might just be a choice between those two. The dimensions of these sheets are typically, 4 by 8 feet wide (i.e. 48 by 96 inches), by 0.5 or 1.0 inches thick.

You already mentioned Great Stuff(r), which is this mysterious stuff that is dispensed from an aerosol can, and it expands to fill the volume you squirt it into. I guess that stuff is good for insulating spaces that are small, or with tricky geometry, where sheets, or pieces of sheets, would be inconvenient. I think, when it cures, the actual material is some kind of expanded polyurethane, but I am not sure about that.

Also I suppose the Great Stuff(r) is great for practical jokes too, like filling up the volume of a locker, or a mailbox.

Anyway, I was going to mention the metric for measuring, comparing, which insulation is better than another.

The honest way to compare one insulating material to another is by using a property called, thermal resistivity, like the values in this table,


The manufacturers of sheet insulation, in the FUS, use a different, related metric, called "R value". Essentially R value is just thermal resistivity multiplied by the thickness of the sheet. So, for example, a 1 inch thick sheet, of some material, will have twice the R value of a 0.5 inch thick sheet of the same material. There is a Wikipedia page that explains this,


and the R values in insulation board sold in the FUS likely has non-SI base units, like degrees Farenheit, per BTU per hour, per square foot, or something screwy like that.

However, if you're standing there in the hardware store, comparing two sheets of competing insulation, with the same thickness, e.g. they're both 0.5 inch thick, then ostensibly the one with the higher R value, is the better insuluator.

Off the top of my head, I do not recall which kind of insulation (e.g. expanded polystyrene vs isocyanurate?) had the higher R value per inch, and I have not yet found an article which explains the subject to my satisfaction.

I dunno. I found an article at least mentions these materials.

Interestingly, it suggests that R values can be temperature dependent,
saying the R value of isocyanurate foam boards is much lower at low
temps, like -20 C.


3 years ago

Even coolhouses use just styrofoarm sheets - simple polystyrene.
An added layer of aluminium foil reflects the warm stuff on one side and the cold stuff keeps cold.
PU foam does work too if you prefer to spray.
A household freezer has about 4-6cm insulation in the tick parts and often only 2-3cm in the thinner parts while a coolhouse has at least 15cm.
All you need is in a good warware store.


Reply 3 years ago

Well that makes it simple. Thanks.