[Greenbuilding] Natural ventilation.

[Frank Tettemer]

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