The short answer
Usually not. Shutting the vents in rooms you don’t use feels like it should cut the heating bill, but in most Northern Virginia houses the furnace or heat pump still runs the same and pushes the same air into the same ducts. In houses with ducts outside the living space, a Lawrence Berkeley National Laboratory study found closing registers raised energy use. It went up, not down.
The part most people don’t know
Your blower doesn’t know a vent is shut. It moves about the same air every time it runs. Close a register and that air doesn’t disappear: the pressure in the ducts climbs and pushes harder on every seam, joint and gap in the ductwork. When those ducts run through an attic, a crawl space or an unfinished basement, the extra air leaks out there, and you’re paying to heat the attic.
The Berkeley Lab researchers tested exactly this, and their advice is plain: closing too many registers, more than 60% of them, is not recommended. Meanwhile the thermostat sits in the hallway, the rooms you left open still have to warm up, and the system runs longer to get them there.
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What closed vents do to the equipment
Higher duct pressure costs more than the bill. On a furnace, less air across the heat exchanger means it runs hotter, and the high limit switch can shut the burners off and start them again, which is one cause of short cycling. On a heat pump, or an AC in summer, low airflow can freeze the indoor coil. A newer variable speed blower ramps up to fight the pressure, so it draws more power and gets louder.
A clogged filter, a crushed flex duct and a blocked return all do the same thing. It’s one problem with different causes: not enough air moving through the system.
The bigger waste is usually the install
The larger loss usually isn’t something you did. A NIST researcher put the cost of common installation faults, like the wrong refrigerant charge, low airflow and leaky ducts, on the order of 30% more energy than the system should use. No vent trick saves that much, and you can’t see it from the thermostat.
When closing a vent is fine
Partly closing one or two registers to balance a room that runs hot is fine. So is easing back an upstairs vent in winter to push a little more heat downstairs. The trouble starts when people shut half the house. If you’re trying to fix a cold room, the answer is usually in the ductwork: a disconnected run, a crushed flex duct, no return in the room, or a duct that lost its insulation in the attic. Our cold room guide walks through it, and leaky ducts covers the attic and crawl space side.
What to do instead
- Open every register and keep rugs and furniture off them.
- Change the filter on schedule. A clogged one starves the system just like closed vents.
- Set the temperature back when you’re asleep or out. ENERGY STAR says its labeled smart thermostats save about 8% on heating and cooling bills on average.
- If one room never gets warm, have the duct that feeds it looked at before you blame the furnace.
What we check
Our heating check is $67 per system, through December 31: furnace, heat pump or boiler. On a furnace, for $229 (regularly $467) we also pull the blower wheel and clean it blade by blade, fit a new filter and set your dampers for winter, which is the right way to send more heat to the rooms that need it. Tell us which room runs cold when you book. For the ducts themselves, our duct cleaning starts with camera photos of your ducts, free, so you can see what’s in there before you pay for anything. The cleaning is $598 instead of $798 for one system in a home up to 2,000 square feet.
Book it
Book the heating check, call (703) 997-9757, or book online from goswiftpro.com/cookiesoffer and a box of warm cookies comes with the visit. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Questions people ask
Does closing vents in unused rooms save money?
Usually not. The blower pushes the same air either way, so closing vents raises the pressure in the ducts and more of that air leaks out through seams in the attic, crawl space or basement. In a Lawrence Berkeley National Laboratory study of houses with ducts outside the living space, closing registers raised energy use.
How many vents can I close?
The Berkeley Lab researchers recommend against closing more than 60% of the registers. Partly closing one or two to balance a room that runs hot is fine.
Can closing vents damage my furnace?
It can strain it. Less airflow makes the heat exchanger run hotter, which can trip the high limit switch and make the furnace short cycle. On a heat pump or an AC, low airflow can freeze the indoor coil.
Should I close vents upstairs in winter?
Easing an upstairs vent partway closed can push a little more heat downstairs, and that’s fine. Shutting most of the upstairs vents isn’t. Setting the dampers for winter does the same job the right way.
