I have a 100FT buried 3 " pipe that carries water and electric to my garage. It also brings in outside air from the garage. IV noticed the air is cool but not near as cold as outside air. Ill have to take a temp scan on a cold day and see what the difference is.An ERV preheats the incoming air. If you have the right topography you might be able to deep bury an air intake pipe or two to take advantage of natural earth tempering of the intake air. .