This is only partially related to automation, but please bear with me... I had a friend tell me he cut his heating bill in half by installing filters on the back side of his return vents (as opposed to just before the blower cabinet) and installing an automatic thermostat to turn the heat down when no one is home.
The automatic thermostat is a no-brainer, but I can't even find fliters designed to attach to the back of the return vents. Is this something anyone else is doing? Can there be significant advantages to this approach? It seems to me that if this was a better mousetrap, all forced-air systems would be designed that way. What am I missing?
Any thoughts are appreciated. Thanks!