Air Conditioning Terms
Roof Air.
Roof air is the most common air conditioning system found on both older and newer motorhomes. The air conditioning unit (usually sized at 13,500 btus) is mounted on the roof of the RV.
The older units simply exhausted the cool air from ducts that surrounded the bottom of the air conditioner, which protruded below the top of the ceiling. These units cooled only the area immediately around the air conditioner unit.
Ducted Air. This term refers to how the cool air from an air conditioner is routed through the motorhome. Older RVs, without ducted air, simply had the air coming out of the bottom/sides of the air conditioners. With ducted air, there are air ducts built into the ceiling of the coach.
One advantage to this system, when it is properly designed, is that cool air from the front air conditioner can be ducted to the rear of the RV, and air from the rear air conditioner can be ducted to the front of the coach. This is great for taking a nap—use the front air conditioner, and have cool air in the bedroom, without all of the noise.
Basement Air. Some of the newer motorhomes have an air conditioner/heat pump combination located in one of the basement storage areas—and have earned the nick-name of basement air. These units have one or two air conditioning condensers and also a heat pump. The heat pump can be used to provide some warmth in the coach when the outside temperature is above 40 degrees or so. These units provide both warm and cool air ducted throughout the motorhome.
One advantage of these units is that they lower the high center of gravity (by taking a lot of weight off the roof) that is so prevalent in motorhomes. However, the chief disadvantage is that they take away from badly needed basement storage space. Also, a heat pump is not very efficient as a heater when the outside temperature gets down in the 20s and 30s—performance at temperatures below 40 degrees is negligible.
