Why Closing Air Vents in your Home Can Strain your HVAC System

Closing air vents in rooms when you’re not using them – it sounds reasonable as a simple way to reduce your AC costs in the summer. As HVAC experts in the city Phoenix, we know full well how high AC costs can get.

It’s not so simple, though. Closing air vents in unused rooms can actually put more strain on your HVAC system more than leaving them open!

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Why Closing Air Vents in Your Home Hurts Rather than Helps

Your home’s HVAC system works a lot like your own respiratory system: the blower manipulates the air pressure in your house’s duct system, using negative pressure to take air from inside your home through the return ducts and positive pressure to return the cooled air back through your home via the supply ducts.

Because the ducts themselves can’t change size, closing the vents in a room throws off the pressure gradients that your HVAC system relies on, dramatically increasing the air pressure and forcing the blower to work much harder than it should. This extra strain can cause significant damage to your blower.

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What Happens

If your home has a permanent split capacitor (PSC) blower, the most common type, closing vents will slow down the airflow because it cannot handle the extra pressure. As a result, there won’t be enough airflow over your AC’s evaporator coil to keep it from freezing over. Once frozen, your air conditioning will not be working and it’ll need to be shut off and the coil defrosted.

Electronically commutated motor (ECM) blowers monitor air pressure, so they will actually increase the airflow to compensate for the change in pressure. However, this takes a lot of energy, and will end up increasing your electricity bill!

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Good Habits Should be First on Your HVAC Maintenance Checklist

There’s no better kind of HVAC preventative maintenance than taking good care of your equipment. This includes using it exactly as intended. Keeping vents open, even in unused rooms, ensures that the blower gets the air pressure that it was meant to when the HVAC system was installed, and will prevent it from experiencing unnecessary wear and tear.

Day & Night Air

Ultimately, closing vents will result in the need to have HVAC preventative maintenance done more frequently than usual, or even worse, you may need to repair or replace parts of the system! If you have other questions or need some maintenance done, please get in touch with us. Our skilled and experienced team will be happy to help you.