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Community and Q&A

Can you safely close air intakes?

GaryJanL | Posted in Energy Efficiency and Durability on

We added solar panels to our house this year and switched our boiler from propane to electric. We have been optimizing our system of radiant heat through the floor by utilizing programmable thermostats and utilizing the variable speeds of the pumps pushing the water through the floor. We noticed today that we have cold air intakes almost directly above the thermostats in two rooms. It feels like the A/C is on while the heat is on. A hand-held laser thermometer is showing the cold air intake at 48 degrees directly above the thermostat which is set at 65 degrees. We are wondering if we can safely cover a couple of those air vents during the winter and uncover them again when we turn on the A/C in the summertime? There is a very large air intake in the great room (main, large open room of the entire house) that will NOT be covered. We do have a propane furnace that is used for emergencies, and the furnace system is used to push the cold air through the house when the A/C is being used. Can we safely cover those two air intakes to reduce the cold air coming into the house in the wintertime? We get VERY cold for a good part of the winter (-20 degrees), so we need to be as energy efficient as we can be. The house is 7 years old, lots of glass but well insulated. Thanks!

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  1. GBA Editor
    Martin Holladay | | #1

    You call them "air intakes," but these are either supply-air registers or return-air grilles, connected to your forced-air system. If properly installed, they should not be introducing any cold air into your house.

    Ideally, your furnace is located inside your home's thermal envelope, and all of the forced-air ductwork is also located inside your home't thermal envelope. All of the duct seams should be sealed with mastic to prevent duct leaks.

    If all of this is true, there shouldn't be any reason that your supply air registers or return-air grilles introduce cold air into your house.

    Something is wrong with your system. Either some of your ductwork passes through an unconditioned area -- with or without duct leaks -- or there is a ventilation duct that introduces outdoor air to your forced-air system, and the HVAC contractor forgot to include a motorized damper on the outdoor air duct.

  2. GaryJanL | | #2

    It looks like it is probably a return-air grille. The furnace is not used except for emergencies (or to distribute cold air from the A/C in the summer). The house is heated via radiant heat from an electric boiler. This return air grille is located in the ceiling directly above the wall where the thermostat is located. It is possible that some of the ductwork has been bumped since various contractors have been up in the attic. The solar panel installers were up there beefing up the roof trusses and then the HVAC guy ran a wire through the attic to a new breaker when they installed the wiring for the electric boiler. There are two of them in two different rooms though that have really cold air coming down through them, so it makes me think it's something else. The solar panel installation could be the reason in one of the rooms, but not likely the other one.

  3. GBA Editor
    Martin Holladay | | #3

    Yes, you can cover the grilles during the winter. But if there is a chance that the attic ductwork has been disturbed, it's possible that a duct has become disconnected. I would have your ductwork checked before turning on your air conditioner.

  4. GaryJanL | | #4

    Roger that. Thank you Martin.

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