I recently built my new home and tried to incorporate all the ebergy efficient options. The house is built on an ICF foundation, I have WallTite Eco foam on the rim joists, walls and entire roof deck and my windows are triple pane, 2 compartment gas filled fixed or casement style. Heting/air conditioning is provided by 7 tons of GeoThermal system. When the initial plans where evaluated I was told I could heat the house with light bulbs and would require very little airconditioning. So far I am a bit disappointed and baffled by the performance of the house. We have recently experienced some fairly warm weather and the geoThermal system in cooling mode has kept the house at the set 73F. What baffles me is in the evenings and night time when the outside temperature drops as low as 64F the house temperature will still rise above 73 and call for air conditioning. it is as if the house is acting as a heat dam and releasing heat back into the house at night. This may seem like a good thing but causes the air conditionig to run excessively or else we must monitor the situation and turn off the AC and open the windows in the evening. This isn't such a bad thing but seems to defeat the idea of building an energy efficient home and relyying on the technology to keep us comfortable. I guess what I am wondering, is this behaviour to be expected. Is the foam in the walls absorbing heat during the day and releasing it back into the house at night? any explanation would be appreciated. I should note that we do have about 85 sq. ft. of glass on the West exposure. Thanks.