In Northern Europe and (slightly slower) parts of North America heat recovery ventilators are becoming standard on new buildings. In my country all new homes ne

In Northern Europe and (slightly slower) parts of North America heat recovery ventilators are becoming standard on new buildings. In my country all new homes need to come with a unit that is at least 90% efficient. Retrofitting such systems isn't that hard, especially if you already have ducted AC. If you don't there are units that can ventilate a single room, they just need a 15cm hole in the wall. You mention home automation, but it's actually interesting with newer houses that are built smarter, there is less to automate: - The ventilation system needs to be sized for the house, then it can be left running all the time (you could turn it off or down when nobody is home, but these systems often consume under 100W of electricity - it's just two fans). - With low temperature hydronic underfloor heating in a concrete floor, it takes so long for the system to heat up or cool down that turning it off when nobody is home will barely affect the temperature. If the system is balanced correctly, taking into account how much energy from the sun each room receives, you can do without individual temperature controllers in each room. Once it's setup the only adjustment needed is to turn it on in the autumn and off in the spring.