This works well, but can be improved. The heat capacity of the building (mostly drywall) is much larger than the heat capacity of the air in the building. It takes several hours for the drywall to achieve equilibrium with the interior air. So you get better cooling if you run the fan for more than 45 minutes. For best cooling start the air exchange as soon as the exterior temperature falls below the interior temperature, and keep running until the exterior temperature is higher an hour or so after sun up.rixer wrote:We live in Ca also. It gets hot during the day and it cools down about 30 degree;s or so at night. We have ceiling fans in every room, energy efficient windows and a whole house fan. Since CA is a dry climate, the whole house fan works great. We run the fan for about 30-45 minutes in the early morning when the outside air is cool. It exhausts all the hot air in the house and replaces it with fresh, cool air. Then we turn the whole house fan off and close up all the windows. It takes a long time for the heat to build back up so with just the ceiling fans running from then on, the house stays comfortable until around 4-5 PM. Then if needed, we run the A/C until about 9PM. This way, we stay comfortable all day and night and only run the A/C 4-5 hours max for the day. Sometimes, we don't even need the A/C with this method.
This does not require a very big fan. A few air exchanges per hour does the trick, this is quite a bit smaller than your AC fan, if it were ducting air directly from the outside. It should be easy and cheap to automate this having a fan that takes outside air, through a filter and into the buildings air handling system. Controlled this with by a couple of temperature sensors and some software. I have no idea why this isn't a standard part of ventilation systems in areas that have cool nights and warm days during some part of the year (which is most of the US).
I guess electricity is just too cheap -- most of my neighbors keep the AC running when it's cooler outside than inside. In theory they could be using the AC as a heat engine to generate electricity, but somehow I don't think that's whats going on.