[GHallof]

Hi Buckfisher. Understood. When AC runs the system draws the warm air from the basement thru the steps into the living space ever so slightly. When the furnace runs it pulls its supply air from the basement area. So the interior warm air is pulled back through the steps into the basement in the opposite direction. The material that i used is lightweight. Just enough to be lightly pulled against the slits in the steps when the AC runs. When the furnace runs the material is pulled away from the slits allowing air flow.

Speaking of the furnace air supply...I was amazed to find just how open the basement area is to draw air from outside the rig. A number of large openings between the body and frame structure. I know this from the DANG critters that made the basement area and every other nook and cranny a place t store and eat black walnuts last year. LOL