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Community and Q&A

Close off rooms?

RickManGR | Posted in General Questions on

Does closing off rooms, bedrooms that are not in use, affect the heating system? Does it save gas, affect the furnace efficient (I have a new high efficiency furnance, or does it matter?
By close off I mean one of two ways: 1. Close the doors to those rooms, 2. close the registers and doors in those rooms.

Thank you, Rick

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  1. Expert Member
    Dana Dorsett | | #1

    It depends on how well balanced and air-tight your duct system is, and how tight the house is. With well sealed well balanced ducts closing the register AND the door to an unused room can save on heating or cooling energy use. But closing off registers raises the static pressures on the duct system, increasing the duct leakage (if the ducts are leaky) and increasing the amount of air handler driven outdoor air infiltration on unbalanced systems. Closing a supply register will somewhat unbalance the duct system, slightly depressurizing the room (assuming it had the proper return path to begin with), but if that room is fairly air tight the impact on air handler driven infiltration is small. If the room is leaky to the outdoors it will increase the air infiltration levels.

    The combustion efficiency of the furnace doesn't matter, but the sizing does. An oversized furnace will be pushing more air, with higher static pressures on the duct system, exaggerating the effects in any changes in duct balance. If it's a 2- stage furnace that's oversized with multi-speed air handler, sometimes defeating the controls that cause it to step up to the second stage will help overall efficiency, due to lower parasitic losses and slightly higher combustion efficiency at low-fire/low air handler speed.

  2. RickManGR | | #2

    Thank You

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