Roof Vents Open or Closed When Running A/C?

gotsmart wrote:

PackerBacker wrote:
Well the hot air should expell through the ac unit but I also leave the vents open just for additional fresh air. My vent have fans in them so leaving them open simply allows me to turn a fan on when needed for places like the bathroom and kitchen area.

If it's very hot and humid, I will sometimes close the vents.

I know that at home, we keep everything shut when the ac is on but we don't have vents there.

Some folks may be confused by the fact that the dashboard air conditioners in many vehicles also pull in fresh air from the outside. It can act as an air exchanger in addition to cooling. Thus cracking a window open allows it to push out hot cabin air and cool the interior faster.

The roof AC in an RV is a closed system (at least the ones that I know of). Just like a window AC in a home, it does not draw in outside air. Opening a roof vent fan doesn't help much unless a window is opened to pull in outside air. This will bring in fresh air, but the trade-off is increased workload on the roof AC.

A roof AC is already drawing in hot air at the ceiling and is pumping out the cold air - which sinks to the floor. Oscillating floor fans would serve to better distribute the cold air throughout the RV than roof vent fans.

Possibly the better roof vent fan solution to use with AC are fans with "dome closed" operation like these Shurflo fans. They can recirculate the interior air by running the fan with the vent cover closed. Granted it is a vertical column of air, but at least it doesn't have to draw in outside air.

I agree, I just like having the vents open and I run the fans as needed.

Up north here in the Airondacks it usually cools off enough at night that the ac's don't kick in (I leave them on 'auto'). I find that the open vents just provide us with some fresh air without opening a window. :C

... Eric