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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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Heating and cooling: Disappearing Heat

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  1.  
    • CommentAuthorgyrogear
    • CommentTimeApr 1st 2016 edited
     
    Desirous to get green, I thought I'd try heating my crawlspace using house air.

    I installed a couple of inline fans and started pulling air out of a warm basement room, and my (warmer) lounge.

    However, the Crawlspace temperature immediately started *DROPPING* ! and kept dropping until I reduced the fans to half-speed, then it rose slightly.

    When I turned the fans OFF, the CS temp returned to its normal level.

    Would appreciate an explanation of what is happening, in layman terms if at all possible :sad:

    cheers,

    gg
    •  
      CommentAuthordjh
    • CommentTimeApr 1st 2016
     
    Dunno, but maybe the breeze is causing evaporation of water from the surfaces?
    • CommentAuthorEd Davies
    • CommentTimeApr 1st 2016
     
    I assume the CS temp you're referring to is the air temperature. Maybe that's been a bit warmer than the ground for a while and the breeze is causing it give up its heat to the ground. Or maybe the breeze is causing movement to suck in outdoor air.

    It's not obvious, though. Also not obvious is how heating more volume follows from a desire to get green.
    • CommentAuthorgyrogear
    • CommentTimeApr 2nd 2016 edited
     
    Posted By: Ed DaviesMaybe that's been a bit warmer than the ground for a while and the breeze is causing it give up its heat to the ground


    Thanks, Ed, I am sure this is true: the ground temp (from reading town water) is 11°C and the CS has been at 15°C and over for weeks...

    Posted By: Ed DaviesOr maybe the breeze is causing movement to suck in outdoor air.


    Aha ! had not even thought of that one, but very likely also (I had a basement window open, for ventilation while the experiment was in progress...).

    Posted By: Ed Daviesnot obvious is how heating more volume follows from a desire to get green


    Good point ! I was just hoping to use solar gain to warm the crawlspace, in order to stop the latter from making the rest of the basement COLD, thereby requiring use of electric heating !

    Posted By: djhthe breeze is causing it give up its heat to the ground


    what would be the exact mechanism behind this ? I remember reading Foster-Tom's explanation of how heat goes into thermal mass (and back out...) and wonder if this would be similar ?

    ======
    Posted By: djhDunno, but maybe the breeze is causing evaporation of water from the surfaces?


    Thanks, DJH, had not thought of this neither. The RH in the CS started off at 82%, and dropped to 80 when the CS got coldest... so sounds plausible !

    thanks, gents, reading between your respective lines, I am tempted to continue the experiment to see if I am actually sending heat into ground mass ! Maybe the efficiency will increase as the weather gets warmer ?

    gg

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