"A myth many people believe is that they can close off some of their supply registers without harm. The system installed in your RV is designed for a certain amount of airflow. If this airflow is restricted in any way it causes the system to function improperly and could potentially cause system failure. Modern systems are designed specifically for a certain amount of air flow and if you restrict that airflow, whether it be by a dirty filter or closing vents, problems will occur. If you have a modern forced air heating system, the pressure load is balanced through the RV. Blocking vents will impact how the system inhales and exhales air; it can throw the system out of balance, causing it to overwork and possibly break down."
The following was taken from "eHow":
"Contrary to popular belief, closing off vents with today's high efficincy heating systems results in little energy savings and can actually raise your energy bill, increased suction in the return air ducts pulls in outdoor air from cracks around windows and exterior doors.
The following was taken from "The Family Handyman"...
"Closing the heat register without sealing the return air duct can actually increase cold air infiltration and cost you more than you thought you'd save.
That's because with the heat vent closed, the suction from the return air duct can pull in cold air from the outside through any cracks around windows, exterior doors or exterior wall electrical boxes.
Second, if the heat duct seams haven’t been sealed properly, the extra pressure from closed-off vents will force hot air through the leaks. That can be as much as 15 percent of heated air into basements and floor cavities instead of into rooms. Finally, if you have a well-designed, finely tuned heating system, closing off too many vents can damage your furnace because it has to work too hard to distribute the air."
