Quote Originally Posted by George2 View Post
The counterflow furnace you have explains the 20"x20" filter a little better. Now I'm more concerned about the return air grille(s). I see a lot of home that are short on return with upflow furnaces and with counterflow furnaces almost always being short.

Can you tell us how your return air is set up?
George2, that would be a single large return. This single level 2500sqft house was built in 94. The current system (N.Gas Coleman Evcon) works great for airflow. No hotspots or cold areas. Same with AC/Heat via a Heat Pump. This is a dual fuel system.

House is super insulated I feel. For example, the current heater quit working one night around 10 PM. It was 69F inside and 40 outside. By morning the inside temp was 62F and outside was 37F. Our climate is mild, we only have about 1 month of temps below 30F and 2 months of temps above 85F. That's why we get away with it...probably.

For today's standards and State/Federal requirements, you are correct.............I would surely need returns for each room.