It’s not uncommon for homeowners to close air vents in unused rooms, believing it will save them money on their home’s heating and cooling costs. After all, if a room isn’t being occupied, there’s no point in heating or cooling it – at least that’s the belief shared by many homeowners. If you’re guilty of closing the air vents in your home’s unused rooms, though, you may want to leave them open. Closing the air vents in unused rooms can backfire in the following ways.

Damage to Air Ducts

Closing the air vents in unused rooms can damage your heating, ventilation and cooling (HVAC) system’s air ducts. HVAC systems are designed to push conditioned air through the ductwork at a specific pressure. When you fully close multiple air vents, it will increase the pressure of the conditioned air.

Too much pressure can damage your HVAC system’s air ducts. The inner walls of the air ducts may burst. Even if it’s just a hairline tear in the air ducts, it will allow conditioned air to escape.

High Humidity

The unused rooms in your home may become more humid if you close the air vents in them. They’ll suffer from a lack of circulation, which can lead to high humidity levels during the summer months.

Air conditioning systems offer dehumidification. They will remove moisture vapor from the air, resulting in a lower humidity level. If you close the air vents in unused rooms, however, your air conditioning system will struggle to dehumidify those spaces. The other rooms in your home may have a suitable humidity level, but the unused rooms will be heavily saturated in moisture vapor.

Poor Efficiency

Your HVAC system won’t become more efficient if you close the air vents in unused rooms. At best, it will have no impact on your HVAC system’s efficiency. Closing the air vents in unused rooms may actually make your HVAC system less efficient.

HVAC systems are available in different sizes. And contrary to popular belief, bigger isn’t always better. If your HVAC system is too big for your home, it will consume excess energy while potentially short cycling as well.

Closing the air vents in used rooms will change the “functional” size of your HVAC system. Your HVAC system will essentially be bigger relative to the size of your home that it’s heating and cooling. The end result is poorer efficiency and the potential for short cycling.