Keep all vents and registers unobstructed.
When air can flow freely through your furnace and air conditioner, it provides quick comfort, costs less in energy bills and improves the functioning of your system.
Make sure that baseboard heaters and air returns free from blockage.
Move drapes, rugs and furniture away from heat registers and return-air vents.
Keep all the ducts and vents open in your home.
Closing or covering up vents is typically not a good way to save on energy costs. Heating and cooling systems balance their load throughout the duct system. If one vent gets closed off, it throws the system off balance. Pressure can build up in the duct work, causing leakage and less air circulating in your home. This reduces system efficiency and home comfort. (ParkCityGreen.org)