[amluto]

> perhaps one way to cut costs could be to over ventilate at night in the summer (after measuring temperature) forcing (filtered) cold air from outside into the house and forcing the existing warm air out.

Setups like this are fairly common, especially in commercial construction. There are “economizers,” various forms of “whole house fan,” and a few HRVs/ERVs with a built in bypass feature. Also windows. HRV bypasses are not especially high flow.

Sadly, most whole house fans are designed quite specifically for houses with vented attics. While most house do have vented attics, there is very little excuse these days to build a vented attic, especially in wildfire-prone areas.