[Greenbuilding] Solution sought for heat rising problem

Topher topher at greenfret.com
Wed Oct 23 13:34:38 CDT 2013


Do you have evidence that it is a problem?  What is the temperature 
differential between the floor and the peak of the roof?  For my house 
(well insulated and well sealed), I have never seen more than a 5 degree 
difference.  At that point I would be wasting more energy running a fan, 
than I would gain.

The math looks like (for my situation): 16 by 8 triangle peak, 32 feet 
long = 2048 ft^3 of air space *  0.018 BTU/ft^3-degree = 37 BTU / degree 
* 5 degrees delta = 184 BTUs.  With a 100 cfm fan we move that every 20 
minutes.  If the heat magically regenerates, we are still only getting 
553 BTUs/hour.  A 100 cfm fan might use 100 Watts or 341 BTUs per hour 
to do that work (plus transmission losses).

This would increase the average temperature of the AIR (only) in the 
house by 0.6 degrees.  Including thermal mass would make it unnoticeable.


Thank You Kindly,

Corwyn / Topher Belknap


On 10/23/2013 9:33 AM, Sacie Lambertson wrote:
> All, currently in Vermont; staying in a lovely house with a big 
> 30'x30', tall 25'+ living room converted from a barn.  In addition to 
> a radiant heated concrete floor, a new pellet stove that blows heat 
> into the space has recently been installed.  About a third of the room 
> is divided by a loft space that forms an extension to the larger room 
> underneath and a bed room above.  The very high ceiling for the entire 
> space is contiguous.
>
> How to bring the rising warm air down to the occupied space below?
>
> The space is well insulated but at the same time it has many windows, 
> at least ten.  It would not be practical nor would it look good to 
> install a beam across the space from which a fan could be hung.  I 
> don't think one can hang a large fan on what would have to be at least 
> a 15 foot single pole.
>
> Ideas/suggestions/solutions for a good way to distribute the warm air 
> would be appreciated.  When winter hits this part of the world, the 
> bedroom space will be overly warm while those sitting below will be 
> uncomfortably cold.


-- 
Topher Belknap
Green Fret Consulting
Kermit didn't know the half of it...
http://www.GreenFret.com/
topher at greenfret.com

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