[DutchmenSport]

If not using your furnace you can close them off. But that vent is the return vent for your furnace. Close it off and you won't have furnace circulation inside the coach area.

I think the cold air is a problem for almost everyone. I took care of mine by taking a different route.

I removed everything in the front pass through compartment. I removed the back wall and looked inside that gigantic cavity under the coach floor. I noticed all the holes and gaps where the Coloplast is screwed to the frame. I noticed all the holes and gaps where the walls connected and where all the wires passed through from one area to the other and the pipes, air vents and everything.

I used about 20 tubes of calking, about 5 cans of Foamy Stuff (expanding foam for insulation) and a whole bunch of screws and closed up the underbelly, all those holes, and every where I could see light coming through inside that cavity.

The end result was, .... no more cold air comes through that vent.

Your furnace needs to blow under the floor. It's designed to do that. The recirculation is actually under the floor. The recirculation of the air pulls from both the underbelly and the inside of the coach through that vent. But, when the furnace is running, it's now pulling all that air through all those holes, pulling in cold air. The end result is, your furnace has to work harder, use more propane to heat the air being pulled in from all those holes and gaps.

After I did the hole, seal-up project, my furnace works a lot, lot better. I have no cold drafts across the kitchen floor (kitchen is in the bottom middle area), and even the air conditioner doesn't have to run as much as it's not pulling in warm air from outside through those same holes.

The warmth of the camper (in winter) and the cooling of the camper (in summer) improved greatly, actually tremendously. Since I plugged all those holes, there has been no need to close off that vent. Air does not come through it any more if the furnace is not running. And it's sealed now, so the air conditioner is not pulling air from their either.

Take the time to plug all those holes and your heat and AC, and all those drafts on the floor will be much more improved.