We live near Seattle, where the summers are enviably temperate. However, we usually have a handful of days each summer where the temperatures spike into the upper 80s and even into the 90s. Because we only suffer for small periods of time, A/C is just not a viable option (though ask me on a day like today, and I'll tell you money should be no object when it's this hot!). We just set up our furnace to let the fan run to help move air throughout the house. I'm hoping this will make the house more comfortable on our rare hot days in one of two ways: a) the air intake is located in the basement, which is considerably cooler and which would make the air blowing out the registers likewise cooler, and b) because just creating air flow can make a hot room more comfortable, rather than letting the air sit stagnant.

Does anybody have any suggestions on what I should do to maximize the performance of the fan? Specifically, I want to know whether I should leave windows open or closed? When and how long should I run the fan? I haven't figured out whether our electronic programmable thermostat will actually control the fan, since I don't expect the temperature to really fluctuate in order to trigger the thermostat.