DD_BobK wrote:
On May 25, 8:56 am, "
wrote:
On May 25, 11:49 am, Oren wrote:









On Sat, 25 May 2013 07:35:48 -0700 (PDT), "

wrote:
On May 25, 2:11 am, wrote:
On Fri, 24 May 2013 19:04:55 -0700 (PDT),
"

wrote:
On May 24, 4:13 pm, Oren wrote:
On Fri, 24 May 2013 15:41:26 -0400, wrote:
On Fri, 24 May 2013 12:38:56 -0700, chaniarts
wrote:

On 5/24/2013 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.

cost.

yes it retains heat. but the earth is a pretty large heat
sink, and it'll win every time. otherwise ground loops for
heating/cooling exchangers wouldn't be an economic win.

i would bet that every pool north of 5 degrees of latitude
would benefit from insulation, most especially heated ones.
no one wants to pay for that up front.

Heating pools is fairly insignificant in Florida.

I'd go so far as to say the water table is warm. (seasonable)-
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Well, it certainly is more than 32F, but it is still below what
you would want far a swimming pool for at least 6 months every
year. No matter what, there is going to be a lot of heat loss
into the ground, and the ground is very wet/conductive in FL.
You need to study the air loss from the surface and the
conducted loss thru the walls and bottom of the pool to see
where your emphasis should be, It is conceivable that you should
drain the pool, put insulation all around the sides of the pool
and then refill the pool.

Huh?
How do you get the insulation behind the concrete?

That would seem to be a good question

For that matter, if you have a liner based pool, I'm
not sure you could do much with that either. Not sure
what you have behind the liner, ie if there is room for
some kind of insulation, like expanded foam maybe?

A good question is why they don't insulate new pools?
If planned for as part of the construction there could be
room for sufficient insulation. And while it would add to
the cost, you would think the payback would be pretty
reasonable, assuming you do some amount of pool
heating.

I can't come up with a single idea as to what the insulation would
be.

It would have to:

- support the weight of a concrete pool or crack the pool

- last for ages under ground

- how would the water table impact the material

Now, on a casino roof top pool, it would seem there would be an easy
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I agree there are some issues. But then insulation is used
with concrete pours for basements that are going to
be heated. Not all the time, but I've seen it done on TV,
like This Old House, etc. Google ICF concrete.

The whole thing of insulation UNDER concrete may seem a bit weird /
counter intuitive .....
did to me when I first was exposed to it.

My initial reaction to insulation under concrete was "how can that
work?"
Concrete is heavy, foam is weak.

BUT the numbers do work....

consider concrete pool 8' deep with a pool bottom 12" thick.

The weight of the concrete PLUS the weight of the water above (for a
1' square column)
is ~150lbs of concrete plus ~500 lbs of water, for a total of 650
lbs.

This may seem like a lot total weight but it works out to a stress of
only 4.5 lbs per square inch.... which is very low.
(The sideways compressive stress capacity of typical framing timber is
more like 400 psi...
so we're only asking the foam to be ~1% as strong as wood)

Soooo... the foam must be able to reliably support this low level of
stress with some sort of "safety factor"

Here's a foam for under concrete apps...
http://foamular.com/assets/0/144/172...f4b6a9fdf7.pdf

FWIW, I got 6" of extruded Styrene under my 4' deep concrete hottub, which has
held up fine for 20 years or so, so far.