Lowering thermostat , how much and closing vents

Discussion in 'HVAC Heating & Cooling' started by lyban, Dec 7, 2009.

  1. lyban

    lyban New Member

    Messages:
    13
    Location:
    Quebec
    I bought a home with an electric furnace. (Canada)
    I have programmed the thermastat to turn down the heat at nightime and also during the day when my husband and I are at work.
    There is one guest room over the garage which gets very cold but we do not use this room very often. So I closed all the vents and closed the door but I can feel the cold air coming under the door.
    I have a few questions. What is the best way to stop the drafts from under and around the door. Or should I leave the vents open in this room.

    also am I making a mistake by turning the heat down too much during the daytime and night.
    How much should we turn heat down at night and during the day? Does this make a big savings or are we just spending the money saved by trying to get the house warm again while there.
    Thanks for any imput.
  2. veesubotee

    veesubotee New Member

    Messages:
    11
    If you are feeling cold air, and no heat is felt coming out of the duct, then the room has become depressurized and outside (cold) air is being pulled in from around windows, or other areas.

    Probably better to have some heat to room (also better for your furnace).

    V
  3. lyban

    lyban New Member

    Messages:
    13
    Location:
    Quebec
    Thank you veesubotee for your reply.
    Would anyone else have an answer for me.
    '
  4. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,924
    Location:
    New England
    There's more than a few issues here. It depends somewhat on how well the house is insulated. If the setback period is long enough, and the room has a bunch of dense things (say a chest or even a dense foam mattress or couch), then when you turn the heat back up, you may get the air temperature to be warm, but then you get the heat sucked out of you when you sit down. But, you normally do savey a couple percent for each degree you drop the temp over an 8-hour period. Comfort levels may or may not be good. It also depends somewhat on how close the heating system's size is to maintaining the temp, or recovering. Recovery takes a larger unit than maintaining it on a design day in the middle of the winter.
  5. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,924
    Location:
    New England
    One concept to understand is that there is no such thing as cold...it is the absence of heat. Heat always is trying to migrate to the cold areas and make everything equal. You can slow that transfer down with insulation, but never stop it. If you are getting cold air from under a room's door, then it sounds like you have a leak - maybe a window, or around the electrical boxes. You may feel the heat from your hand being sucked away if the room is very cold, sort of like putting your hand near the open door of the freezer. If there is an actual draft, the dampers may not be closing fully, and the small volume of air from the furnace that does get through is so small, it is just pushing colder air out. Ideally, each room would have a return duct, and it wouldn't come out under the door, but that isn't done as often as it should be.
  6. lyban

    lyban New Member

    Messages:
    13
    Location:
    Quebec
    Jim

    The cold area coming under the door is from the bedroom that we are not using and therefore have closed all the vents so that there is no heat coming into that room. The house is old and poorly insulated and this particular room is also over an unheated garage.
    What I am asking is is it better to heat this room and not close the vents or should we close the vents and try and stuff and seal the door going into room.
  7. jadnashua

    jadnashua Retired Defense Industry Engineer xxx

    Messages:
    21,924
    Location:
    New England
    Are there any water lines that might freeze if you fully shut it off? Anything running in the walls or floor in the room being shut off? If not, the entire wall will appear sort of like an exterior one, buffered by the volume, and may make those near it colder. It's rare to have insulation between interior rooms, so you may notice the fact that room is no longer warm. It's worth a try, unless, as I said, you might end up freezing a pipe and creating a big mess.
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