ransley wrote:
On Nov 3, 12:03 pm, "Edwin Pawlowski" wrote:
wrote in message

Because having just air means the air can move and readily transport
heat from the warm wall to the cold wall. With insulation filling
the cavity, there is still a lot of air there, but it's being held in
place by the insulation, so it's far more difficult for an air
molecule to go from one wall to the other.

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Exactly. There is an optimum for every insulation material, be it
fiberglass, cellular foam, cellulose, etc. One big space is not so
good. divide it into four and it is slightly better, divide again
into four hundred it is better, but divide it into 40,000 spaces it
is great, but then if you divide that into 80,000 spaces the solid
material between the air cells is transmitting the heat again. That
is why concrete walls are so poor compared to even thin layers of
insulation.

Heat is always trying to move to the cooler places. With most
materials it moves through liquids faster than solids where it moves
faster than air.

How do you divide foam

My bartender just scrapes it off with a knife.