Stay Comfy Blog

FAQ: Does Closing Vents in Unused Rooms Really Cut Cooling Costs?

AdobeStock_56922809 (1).jpegWe’ve probably all heard the sage advice: “Just close off the registers in the rooms you’re not using. Closing vents will save on energy costs if you’re not cooling (or heating, for that matter) those rooms.” But is that really true? And if so, how much can you actually save? We checked in with Keith Hill, resident HVAC expert at Stay Comfy to find out.

An Integrated System

Your HVAC system isn’t simply a combination of parts that conveniently came together. It’s actually a carefully designed system meant to accommodate the right amount of air and airflow to heat and cool your home. “HVAC distribution systems are engineered, meaning the ductwork size, location, configuration, and the registers and grilles, both in size and quantity, are selected to direct the correct volume of air where it’s needed,” Keith points out.

The whole system is designed to conduct the precise amount of air and distribute it where it’s needed to match the heat loss or gain—to heat or cool—each room. As Keith notes, “The HVAC professionals that designed your system did not oversize the system. Why would they?”

Airflow is Key

The airflow through your HVAC system is what conducts heating and cooling to all parts of your home. That’s pretty obvious, especially if you’re near a vent when the heat or AC kicks in. But what may not be as obvious is that airflow also returns through the system. Both the air supply—the air that you’re aware of venting into a room—and the return airflow are based on a calculated pressure that keeps the system running smoothly and efficiently. And that translates into effective heating and cooling for your home.

Disrupting the Balance

If you decide to close off registers or block grilles to interrupt the planned airflow, you’re also forcing the system to adjust to a different pressure than it was designed to handle. You’re asking the whole system to work harder than intended. And that could become problematic. If your system is operating at a sub-par level, that means your overall cooling and heating isn’t going to be as effective. But that’s not where it ends.

Keith explains it this way: “If you upset the balance by closing off registers you may create a problem of low airflow, which if severe enough, will damage your furnace and air conditioner. Both of these require a minimum amount of air to work properly and efficiently. The small amount of savings you may gain by not heating or cooling a room or two will be more than offset by the efficiency loss.”

If prolonged or severe enough, that low airflow could even cause your furnace to overheat or your AC coil to freeze. If not caught in time, that could even damage your compressor. Now you’ve really got a problem.

An Alternative to Closing Off Vents

If you have rooms or whole areas of your home that you don’t use for part or all of the year, there is a better solution. It’s called zone heating and cooling or zone control. Zone control lets you set different temperatures for different rooms or areas of your home. So no more closing vents in an attempt to save on fuel costs. Many new home constructions have zone control, but you can also retrofit a home to include it. If that sounds like it might be the right solution for you, talk to a reputable HVAC professional. You can find one in your area using our dealer locator.

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