||05-09-2007 01:50 PM
The temperature inside your house should be.... whatever you are comfortable with.
Typically AC systems are sized for an indoor temperature of 70F-75F. While "studies" have indicated that the typical comfort level for humans is 75F and 50% relative humidity, everyone is different. Seems like most guys I know want it between 69F and 72F, and most women want it between 73F and 77F (summer time, in cooling mode).
That being said, if you live in a humid location, you need to think about humidity; that is, when your AC unit runs, it also dehumidifies. If you live in a "leaky" house, in a very humid climate, and you set your AC for a higher temperature, you are likely letting the humidity levels in your house get fairly high and risking mold/mildew issues. Also, if you have an AC system that is oversized for your house, and you set it for a nice cold temperature, the system will cycle (turn on, cool the place down to that temperature, and then shut off) too quickly, and thus not run long enough to adequately extract enough humidity from the air. That can promote mold/mildew growth as well (and a "clammy" feel in the space).
Typical AC systems are designed for outdoor air temperatures that are a "worst-case" for the area in which you live - in most of America, a summer temperature between 90F-96F, and humidity in the 40-55% range. They are then sized such that the supply air temperature is somewhere in the ballpark of 55F. The target is to have a 75F space (thus, 20 degrees difference across your cooling coil, known as "delta-T"). This commonly varies within about 5 degrees (usually with the supply air temp being slightly higher and the room/return air temp being slightly lower), but the closer you can keep it to the 20F delta-T, the more efficiently your system will be running.