On May 24, 12:22*pm, Oren wrote:
On Fri, 24 May 2013 10:29:58 -0700, chaniarts

wrote:
No, there is no insulation between the pool and the ground. *It doesn't get that cold down here for that kind of thing, I would think.

you'd be wrong. ground temp is always less than air temp, unless you're
living on a volcano. so, it's always a heat sink 24x7. insulation around
a pool is always a winner, but it's hard to put in after the pool is done.

I worked in pool construction as a teen, In Florida, no less. Not once
was insulation involved in the construction of the in ground pools.

The *cement gunite is ~ 8 inches thick, full of steel rebar and
retains heat for some time.

the R factor for concrete is terrible
about 1.5 for 8" of reinforced concrete. In ground spas & pools
lose
a LOT of heat to the ground.

8 inches thick, full of steel rebar and retains heat for some time.

if that was true we wouldn't need very large pool heaters...

the heat capacity of concrte is only 1/4 that of water.