[Greenbuilding] Natural ventilation.

[Alan Abrams]

can't quantify it for you, but my hunch is that a 4" ceiling vent relying on
stratification and not mechanical force is not large enough to overcome
static pressure and induce significant flow through a 4" ground
intake--particularly if the ground intake is long enough to cool incoming
air appreciably.  A venting skylight might be a better option, assuming
summertime solar gain and wintertime thermal loss were factored in.
regardless, many variables need to be considered...


*Alan Abrams**
Abrams Design Build LLC*
*A sustainable approach to beautiful space*

6411 Orchard Avenue Suite 102
Takoma Park, MD 20912
office  301-270-NET- ZERO (301-270-6380)
fax      301-270-1466
cell     202-437-8583
alan at abramsdesignbuild.com
www.abramsdesignbuild.com



On Mon, Aug 29, 2011 at 8:20 PM, Frank Tettemer <frank at livingsol.com> wrote:

> Hi All,
>
> Here's a ventilation question, for all the fresh air fans on this list.
> I'd like to use gravity ventilation, and I need to plan a way of opening
> and closing the vent.
>
> We're building a small straw bale home for a couple this year that has
> engineered trusses.
> The upper cord, defining the roof surface, is 6/12 pitch.
> Inside, the ceiling in one area of the house is a 3/12 pitch.
> The walls are 8'-3" at the truss plate, and the central high point in the
> ceiling is 10'6".
> The home will be heated with an ESSE wood cooker, and has a 4" diameter ABS
> pipe emerging from the floor, behind the ESSE, bringing in fresh air, from
> below ground, and will be ducted to the combustion air inlet on the wood
> stove for the winter.
> During the summer, a 4" TEE in this air pipe will allow earth-cooled
> outside air into the home.
> (We've provided condensation drainage, as well as a straight clean-out,
> from the outside of the home, to deal with potential mildew troubles.)
>
> What I would like to do is provide a 4" exhaust vent, up at the peak of the
> interior ceiling, to complete the ventilation scheme, which relies on
> gravity to power the flow, i.e., hot ceiling air vents upward, through the
> attic space, while colder earth-tempered air is drawn in from the outside in
> the North shadow, to the centre of the home, near the stove.
>
> I know that while windows are open, the earth-tempered air may not flow
> inward with any serious pressure.
> But the hot air, at ceiling height of 10'-6" will surely flow upwards and
> out, no problem.
>
> Back to my original question around ventilation. How do I open and close
> that 4" ceiling vent?
> Is there anything on the market that has very positive closure, and could
> be used?  A good closure system will be necessary during the long winter
> months, here in Ontario, near Algonquin Park, which has weather similar but
> colder than Ottawa, Ontario.
>
> I'm sure this has been done before, and there must be a practical way to
> control this venting.
> Any ideas?
>
> Frank
>
> --
> Frank Tettemer
> Living Sol ~ Building and Design
> www.livingsol.com
> 613 756 3884
>
>
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