My house is three stories plus a basement, and, not surprisingly, there's often quite a range of temperatures across levels. My current central forced air system has a single thermostat on the second floor, and often kicks into cooling or heating mode, when I feel like some clever air circulation (i.e. just the fan running, with the right intake ducts open) would do the trick.
For instance, it's often hot on the second or third floors while the first floor is cool, and just circulating the air should drop the upstairs temperature without having to run the power-hungry AC condenser. Alternatively, the whole house might be hot, but the basement is cool (even in the summer), or the outside air is cooler than inside (e.g. in the evening after a hot day). It seems like having a basement or external intake for this purpose would be a more efficient source of cool air.
My questions, then, are roughly as follows:
1. Is it plausible that some plan along these lines would actually save power, or is this unlikely to be significant in practice?
2. Are there thermostats that have temperature-controlled fan operation, as opposed to temperature-controlled heater/AC operation? Or maybe fan operation triggered by the temperature difference between multiple sensors (one on each floor)?
3. Assuming the answers to the above are yes, would it make sense to install basement or external intakes, along with automatic opening/closing of the intake vent and a basement/external temperature sensor?
My limited searching at local home improvement stores and online hasn't turned up any sufficiently advanced thermostats that would be able to handle this..
Thanks in advance for any thoughts or suggestions.