It sounds like the heat pump isn't working correctly. Have you noted any freezing on the outside unit in the winter. If so it is an indication that the Freon is low. I think your home warranty goes through 03/22/10. It might be good to have the unit checked before then.

I think I recall the HVAC unit is on the west side of the house. Does the late afternoon sun hit the unit in the summer? This can cut way down on it's ability to cool.

I checked the inspection report and found The inspector noted two passive vents on the roof and soffit vents to bring in air from the eaves, he noted R32 insulation.

My first suggestion is to check the HVAC unit then consider adding ridge vents. (You can never have too much ventilation.) You may try checking with the neighbors as well.

HVAC systems are designed to handle the normal high and low temps in a given area. Last summer was unusually hot. It may be that the unit was having trouble because of the unusually high temperature and humidity.

Please let me know if you aren't able to work out the problem. There is a way to build an automated water spray system that mists water onto the outside coil when the unit is running in teh summer. I build one last year for our house.

Philip