bluhorizan

Hi: I've asked myself the same question as you are regarding insulation of the pool shell. The biggest heat loss is through surface evaporation. A pool cover reduces that significantly. However insulation of the pool shell will also substantially reduce heat loss. Consider that the temperature of the soil surrounding the pool varies from 30 degrees in the winter to 60 degrees in the summer (5 feet below grade) and you are trying to maintain a water temperature of 85 degrees, there will be a significant gradient resulting in ongoing heat loss. The R value of concrete is essentially zero and a fiberglass shell is slightly higher. Adding 2 to 4 inches of spray on foam or rigid polystyrene insulation will dramatically increase the R value and markedly reduce heat loss from the pool. This will reduce energy heating costs noticeably. The cost to do this will probably be in the $1000 to $2000 range. I think its worth pursuing. Good luck!

look at www.poolnut.com He did exactly this to insulate a gunite type pool with very good results