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Energy saving idea?

Discussion in 'Home Power and Microgeneration' started by JimmySchmittsLovesChocolateMilk, Dec 2, 2004.

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  1. woudln't Your floor would get cold from the cold attic air, cooling the air
    above it, and forcing your furnace to run more often?

    Once you cyled the air completly once, the radiant heating from the earth
    would take a while to warm the air under the house again,
    more likely it would be the heat escaping thru the floor that would be
    warming the air under the house,
    so I think the net benifit would be little to none, ...
  2. John Harlow

    John Harlow Guest

    What would be the problem with ducting cool air from under a house to the
    attic in warmer months to help with cooling, and just the opposite in the
    winter to help with heating?
  3. I'd be concerned about the quality of air from under the house. Mold spores
    could cause problems.
  4. John Harlow

    John Harlow Guest

    Interesting - wouldn't they also cause problems under the house?

    How about a filter, or a heat exchanger made with some ductwork?
  5. Sure, mold is a growing problem in homes.

    OTOH, bringing in fresh air may help the problem. The filter and heat
    exchanger would help.
  6. xrongor

    xrongor Guest

    interesting idea.. i like it.

  7. John Harlow a écrit :

    Depends what "under a house" means. Is the house elevated? Is the house
    on a concrete foundation? etc etc..

    Do you mean taking cool air from an existing cavity or laying a couple
    of pipes under the house and getting air from there? If its the second,
    it's reasonably common (it's called a Canadian Well here in France). If
    it's the first, it would depend on the air temperature, the thermal
    mass's capacity and fan running costs (cold air won't rise on its own...)

  8. Good point, but there are attics and there are attics. If the attic is the
    unoccupied space above the rooms and the insulation is between the joists,
    you are correct. If the attic is the livable space above the second floor
    and the insulation is in the ceiling, the idea would work to some degree.
  9. John Harlow

    John Harlow Guest

    I'm thinking of the somewhat typical house here in the US (like mine of
    course ;) with a small crawl space over dirt.
    I am thinking about moving the air from the existing cavites using a blower.
    It seems to me, for the price of running a couple hundred watt blower, there
    could be substantial energy savings at least in the summer months.
  10. m II

    m II Guest

    It's only a matter of time. A low 'cubic foot per minute' fan will
    just take a bit longer to do the job. As cold air is heavier per cubic
    foot, he just has to overcome the density difference caused by the
    temperature variation and whatever resistance to flow may be in the
    ducting. Large ducts = less resistance.

    A one or two ampere motor (approx. 100 to 200 watts) can
    deliver/remove a lot more energy in heated air that it uses up. That's
    just a guess for an average bathroom fan motor.

    all in my humble opinion, of course..

  11. Gymy Bob

    Gymy Bob Guest

    A bathroom fan motor would never push hot air down ten feet or cold up ten
  12. Guest

    Would you have any evidence for this article of faith?

  13. m II

    m II Guest

    I respectfully disagree. I stand by my statement that it would only be
    a matter of longer time. The amount of air will vary a bit per time
    period, but it WILL keep moving.


    A fan is a "constant volume" device where the transported volume is
    the same, no matter air temperature and density, if all other things
    are equal. Only the mass flow through the fan varies with air
    temperature and air density.

  14. Gymy Bob

    Gymy Bob Guest

    Bathroom fans have a hard time pushing 55 cfm through a 3-4" pipe 20
    horizontal feet. They are made to vent smells and humid air horizontally

    Do the research and think!
  15. Guest

    Awww. Do they complain?
    You might do this and find that the density difference between hot and
    cold air in houses creates a negligible pressure difference compared to
    the static pressure rating of the fan or the friction loss of a long duct.

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