Many homeowners faced with onerous summertime energy bills attempt to save energy and money by closing off parts of their home or shutting some of their central air conditioning vents. It makes sense that closing the vents in unused areas of the home would direct more cool air to other areas of the home and would result in lower energy usage and reduced electric bills. However, studies have shown that closing more than just one or two vents did not result in a cost savings and can even cause damage to the system.
Most HVAC systems installed in the past twenty to thirty years were carefully designed to meet the needs of the home. Efficient operation of these systems depends on the right amount of air flowing through the system. If a homeowner closes some of the supply air vents, the air flow within the system is restricted and duct pressure rises.
As the pressure inside the ducts increases, so does the amount of conditioned air that leaks from the ducts. Studies have shown that this increased duct leakage offsets any benefit gained from closing some of the home’s air supply vents, especially if the ducts are run through non-conditioned space such as an attic or crawlspace.
In addition, the reduced airflow through the system can cause ice accumulation on the coils. This ice further blocks the airflow and reduces the cooling airflow.
Your heating and air conditioning system was designed to operate most efficiently with all of the air supply ducts open. To save money on air conditioning costs, talk to your HVAC technician about duct sealing to reduce duct losses and having an HVAC system efficiency analysis performed to find ways to improve efficiency of your heating and air conditioning system.
