Swimming pool insulation saga continued...

[Mr Sandman]

Those of you who have followed my pool saga, let me update you.

In summary, my swimming pool builder is trying to convince me not to insulate my pool because he feels that the ground will insulate it and heat it. However this makes little sense to me because the ground being at a lower temperature to the pool i.e. 11 degrees (in the summer time, lower in the winter/spring)compared to a goal pool temp of 30 degrees. To me, the higher conductivity of the wet clay surrounding the pool will suck heat out of the pool, but with insulation, this will be greatly reduced. However i cant seem to convince him!

I have suggested an experiment; to take a sample of clay from the depth that the bottom of the pool will be and heat it to the same temperature it is at that depth, then take a sample of insulation at that same temperature, and put one hand on the insulation and the other hand on the clay and see which feels cooler. Which ever one feel cooler is cooler due to the fact that heat is being drawn away from the hand.

Does this experiment sound relatively sound and representative?

Cheers

Greeny

[The Natural Philosopher]

Your builder is essentially correct., and your exeprieriment will confirm your prejudice, but actually prove nothing.

[John Rumm]

It would make more sense to dig two holes to the same depth, insulate one, insert liners in both, and heaters in both, fill, and cover with a thermal cover.

With a non thermostatic heater you would expect the pools to each reach different equilibrium temperatures. With a thermostatic heater, you would expect the insulated pool to consume less energy to maintain the temperature.

While I accept the argument that the soil may be a poor insulator - but you do have lots of it, this seems to ignore the fact that it does have a large thermal mass that will take energy to heat. The more you prevent this being heated the better. A sharp thermal gradient in a highly insulating but low thermal capacity material, is going to require less energy to maintain the insulation at halfway between pool and ground temperature on average. The type of soil will also have an impact - if there is any water mobility in the soil then this will allow additional heat loss due to convection.

[Angela]

Having owned an outdoor pool for a number of years (and I would never own another!) you will lose all your heat from the surface of the water not the soil. If you want to save energy heating it, then I suggest you cover it with a really good thermal cover, and never actually take it off and use the pool!