Question about saving electricity

Discussion in 'Homesteading Questions' started by Ravenlost, Jun 29, 2006.

  1. Ravenlost

    Ravenlost Well-Known Member Supporter

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    We have a two story house with central heating/cooling units for each floor. At night my hubby sets the thermostat really high downstairs and turns the thermostat upstairs really low...usually a 15-20 degree difference between the two. He says he's doing this to save electricity.

    Heat rises, right? So if it is warmer downstairs the heat is going to come up the stairwell and make the upstairs unit run more, right? So how can doing this save energy?
     
  2. WisJim

    WisJim Well-Known Member Supporter

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    This is such a complex situation that the only way to get an accurate answer is probably to try different combinations of settings and see what your actual savings are. If heat from downstairs actually does make the upper unit run more, it MAY actually use less total energy than having both units running. Why not close the stairwell door, or add a door that you can close, if it would save energy?
     

  3. JAK

    JAK Well-Known Member

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    Sounds like he is bascially turning it off upstairs, so it will be a bit cooler upstairs. Many people prefer to keep bedrooms cooler than the rest of the house. If upstairs is cooler than downstairs more heat will rise from downstairs but you will still lose less heat. Similarly in summer if you don't mind it being a little warmer downstairs during the day but you want it cool enough upstairs to sleep at night you could turn the air conditioning off downstairs and just run the air conditioning upstairs just enough to be able to sleep comfortably at night. This will save energy, and some of the cold air will work its way downstairs so it won't be so bad down there during the day. Also, just running one unit rather than two might save some money, as the systems are most likely oversized for most days. If it is really hot or really cold then you would likely run both, though at different temperature settings. All that said you would probably accomplish much the same thing just be setting the thermostats in each zone to what you really want, with setbacks when you want. As long as you are not heating and cooling at the same time, or even during the same week, you are OK. That would be bad. There should be a period of a few weeks each year where you need to do very little of either, even during a period with hot days and cold nights. Every house should have enough insulation and thermal mass to deal with daily cycles, perhaps even weekly cycles.
     
  4. Michael W. Smith

    Michael W. Smith Well-Known Member

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    Depending on the layout of your house, I would say your husband is right. However, if there are any registers between floors, (I'm sure you already have those closed) but it would help to put something else over them to insulate them more - a blanket, even just a sweatshirt).

    Also, could you put up a curtain in the stairway at the bottom of the steps? Even just a blanket would prevent warm up from coming upstairs and cool air from going downstairs.

    At least your husband is trying to save electricity. How many people go to bed leaving the air on downstairs even though no one will be down there until the next morning?!?
     
  5. Ravenlost

    Ravenlost Well-Known Member Supporter

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    Hmmm...I'm more confused than ever now! LOL...

    There's no door to close the upstairs off from the downstairs. The thermostat is in our bedroom, but hubby won't close the bedroom door (his dogs need to go in and out during the night).

    You can actually feel hot air rising up the stairs. I guess it's trying to get up to the attic where there is no ventilation (shouldn't there be an attic fan to draw the heat out?).

    During the day he turns the upstairs to 80 and the downstairs to 76, which isn't a big difference, but at night he puts the downstairs on 80 and the upstairs down to 72 or lower. Some nights the thermostat never gets below 74, which means the unit has been running all night long. I just think if he put both on about the same temp the upstairs unit wouldn't have to work so hard.

    When I met him he had never opened a window in his house. I grew up without central heat and no air-conditioning at all (in Alabama). It's still getting down into the low 70s at night and I think we could just open the windows and keep the ceiling fan running without any air conditioning.
     
  6. Jack in VA

    Jack in VA Well-Known Member

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    " It's still getting down into the low 70s at night and I think we could just open the windows and keep the ceiling fan running without any air conditioning."

    Theres your answer.
     
  7. Ramblin Wreck

    Ramblin Wreck Well-Known Member Supporter

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    Your hubby probably just likes the bedroom cooler for sleeping. I would. A few years ago I saved $'s by putting in an energy efficient window unit in son #2's upstairs bedroom. He worked nights and liked the room really cool for sleeping during the day. It was much cheaper to zone cool that one room than it was to turn down the thermostat for the upstairs central unit to a ridiculously low level.
     
  8. Michael W. Smith

    Michael W. Smith Well-Known Member

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    Hmmmmmm. Perhaps you would be right then to leave the downstairs air on as well? But is there anyway to put something up (a curtain, a blanket at the bottom of the steps) to prevent the warmer air from coming upstairs?

    Yes, there should be something to draw the hot air out of your attic. Even opening up windows up there would help. With the way things are now, at nights your second floor is "sandwiched" between 2 warmer areas.

    Your husband turns the air down to 72 to lower? Well, you sure wouldn't want to live with me. For years we did without air, and then with a job position change I am in now in air all day. I can't do without it now, and at night especially! We have a window air conditioner in our bedroom and I have it turned to 67 or 68. Wife complains, but I have to have a cooler room to sleep ok.

    As for letting the dogs in and out and can't close the door. Wait until your husband falls asleep and then get up and close the bedroom door!
     
  9. Cindy in NY

    Cindy in NY Well-Known Member Supporter

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    My DH who is an electrical engineer says your husband is right. After a few hours the entire house should attain thermal equilibrium. Your original statement might be true if you ran the air conditioning upstairs and the furnace downstairs at the same time. If the furnace is off and the air conditioning is on upstairs, the laws of physics dictate the house will become cool with just the upstairs unit on.
     
  10. SolarGary

    SolarGary Well-Known Member

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    Hi,
    If it cools down at night, a whole house fan that pulls air into open windows and exhausts to the attic works well -- it both cools the air down and creates some breeze. It also cools the thermal mass of the house down to the outside air temperature, so, the next day the house starts out cool and the AC does not have to be started so early in the morning. There is some material on the whole house fans at the link below. Running a whole house fan is much cheaper than running AC.

    Probably your best bet for saving energy would be in things like upgrading your insulation, reducing air infiltration, and shading windows (preferably on the outside) to reduce heat gain -- east, south and west facing windows can gain a whole lot of heat on a sunny summer day.
    Some ideas here:
    http://www.builditsolar.com/Projects/Cooling/passive_cooling.htm
    and here,
    http://www.builditsolar.com/Projects/Cooling/Shading/Shading.htm

    Gary
     
  11. Wolf mom

    Wolf mom Well-Known Member

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    I installed a fan in the stair well where the ceiling light was & kept it running on low most of the time. Seemed to be cheaper than enclosing the stair well to keep the heat from rising. Worked well.

    It'll be a loooong time before I buy another 2 story or loft type home for that very reason.