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The Dangers of Closing Air Vents in Unused Rooms

Many of us close air vents in unused rooms to save money and energy. But here’s the kicker: closing the vents actually causes your AC, heat pump, or furnace to work harder. This can damage your system, put your health and safety at risk, and cost you more money in the long run. In this month’s blog, the home comfort specialists at Main Stream Mechanical explain the problems caused by closed air vents and offer suggestions on how to increase your system’s working efficiency and decrease your energy costs.

1. Lost Efficiency Your HVAC system is sized to efficiently condition and heat your home. Closing the vents doesn’t improve its effectiveness and here’s why: Closed registers force the same amount of air through other ducts. This increases pressure in your air ducts and makes your HVAC system work harder to distribute the air where you need it. Not only does this decrease efficiency, but it compromises the blower.

  • If you have a Permanent Split Capacitor (PSC) blower, a closed vent will cause the blower to slow down because it can’t manage the increased pressure. A slower system takes longer to bring your home to its desired temperature.

  • An Electronically Commutated Motor (ECM) blower can adjust its speed to varying conditions. However, when you close vents it will boost its capacity in order to overcome the extra pressure, leading to larger energy bills.

2. System Damage

When you close the vents, the PSC blower slows down, and delivers less air to the air conditioner’s evaporator coil. Reduced airflow causes the coil to get too cold and freeze, forcing liquid refrigerant back to the outside compressor, and damaging it. Additionally, low airflow can cause your furnace’s heat exchanger to overheat and possibly crack. If you damage the compressor or heat exchanger, you’ll need to repair or replace it.

3. Increased Duct Leakage Closed air vents can cause leaky ductwork to worsen. When you close the registers in unused rooms, the pressure builds and turns those small leaks into costly problems.According to Energy Star, the average home loses about 20 percent of air through small leaks and poor connections in the ductwork.

4. Carbon Monoxide Risk When you close the air vents in unused rooms, it’s much easier for the heat exchanger to crack, which can release deadly carbon monoxide into your home.

5. Mold Growth When you close any of your HVAC system’s registers, condensation could occur in other rooms because the air coming out is too cold compared to the room’s temperature. The condensation on the register can result in mildew and mold growth.

System Solutions

In essence, closing vents in unused rooms forces your system to work overtime. In reality, you’re paying more, decreasing your system’s life span, and potentially putting your health and safety at risk. The more vents you close and the longer you keep them closed, the more likely you’ll experience problems.

Still have High Energy Bills?

If you still struggle with higher-than-normal energy bills, you may have other problems such as air duct leakage or an inefficient furnace. An inspection by a home comfort specialist can identify the source and repair your system.

HVAC Installation, Maintenance and Repair in NH and MA

If you have issues resulting from closed vents, contact the home comfort specialists at Main Stream Mechanical. Our HVAC service technicians will address the problem and repair your system. We service many locations across Massachusetts and Southern New Hampshire including Haverhill, Amesbury, Newburyport, Rowley, Topsfield, and Boxford. Powered by Sprout


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