[Dave W]

I fully understand the cold air return system in a S&B home. That return air is plumbed into the inlet side of the furnace squirrel cage blower. An RV - that return air just becomes 'common' air in the basement and belly area and requires more Btu input to replace that heat which is lost by recirculating through that virtually open to the atmosphere basement. Those return air grilles without a plenum/ducting then becomes useless as 'preheated air with a slightly open window or roof vent doing about as much good for good heat circulation. Add some ducting back to that inefficiant furnace from the grills and you will probably pick up several efficiancy percentage points.


Now, with that said - yep, I block off those grilles to preserve a/c cool air or cold air on a chilly morning seeping in. Other then that, it is what it is - an inefficient system that should be better (but only at an added cost to buy an RV)