Most homeowners have a bad habit of closing their vents whenever their room is not in use. Little did they know that closing vents can actually place a high level of strain on their air conditioners and reduce their efficiency. What happens when you close your vents? If you are using a permanent split capacitor (PSC) blower, closing your vents can cause a rundown of oxygen in the system. The blower will slow down and it can’t overcome the pressure inside. If you have an electrically commutated motor (ECM), closed vents can cause it to ramp up to adjust on the pressure thus causing high energy bills. Since closed vents deprive the system of proper airflow, the evaporator coils will likely to get cold and freeze. The refrigerants would flow back and damage the compressor. This can also allow for the heat exchanger to overheat and break. If these happen, repair can be very expensive. You might just replace your entire outdoor unit and heating system instead. Closing your vents also leads to longer time cooling your home. This doesn’t sound like a saving mechanism; rather, it doubles your utility bills. It even allows for air leaks in your ducts to get worse. Closed vents increase pressure in the system which forces more air through the leaks. It causes the leaks to open even more allowing your needed air to flow out of the system. However, opening your vents won’t solve air leak problem. You must call an HVAC professional right away. In addition to these, you will also experience comfort issues due to poor airflow, increase in mold growth and condensation during the cold season and increased infiltration due to leakage. How closing vents could work? Multi staged variable speed ECM blowers allow for closed vents in signaling the unit to lessen the heat produced. This happens in a properly designed zone duct systems only. Other that, you can be subjected to all the dangers mentioned above. There are many saving strategies you can use for your HVAC system. Be sure to remove closing your vents from your long list of saving tips. Or else, you might end up spending too much.