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GBlist: Natural air flow

To answer the question 
>From: "David F. Lambertson" <dlambert@falcon.cc.ukans.edu>

I'll offer one suggestion: the building envelope is very airtight, thus 
minimizing the stack effect, which you characterize as "the rising hot air 
syndrome".  One way to verify that this is the case is to air-tightness test 
the house.

Stack action is the air flow that is generated when warm air leaks our the 
cracks in the upper portions of the building, replaced by cooler air that 
leaks in at the base of the building. The leakier the house, and the colder 
the weather, the more pronounced it will be. In a tight envelope, there is 
no chance for the air to escape or cold air to infiltrate, so there will be 
a more even temperature distribution. 

Dome structures often are inherently quite airtight when waterproofing 
considerations are made.

Applying the airsealing considerations (and good, balanced insulation levels 
throughtout) to a more conventional structure will achieve the same results. 
But the operative concept is airsealing the envelope of the building. This 
means special attention to construction details. (of course, attention must 
be given to the "house as a system" - this also means that a mechanical 
ventilation strategy has to be considered).

> two years ago we had the pleasure of house sitting the home of an architect
>friend who sells the design and the engineered structure of her unusual
>house in a kit form.  Built in the shape of a wooden egg, beneath the
>clerestory windowed dome is a steel collar holding the rafters together.
>The open interior is a two floor plan with the second floor covering two
>thirds of the first.  There is a gap around perimeter of the second floor to
>allow air to more easily circulate from below.  We were there in early
>November when we needed a bit of heat from the single source, a wood stove.
>I was interested to experience none of the rising hot air syndrome I am used
>to in a 'normal' house; indeed the entire house felt evenly heated and very
>comfortable.  I would like to know why.  Is it the dome shape or the
>perimeter gap or both?

>However, I am wondering if the
>principles of the design that allow such a naturally good air flow as to not
>feel extra heat or cold anywhere might not be applied to a somewhat more
>conventional structure.  Specifically I need to know how it works and does
>it need a curved surface to do it.  And, as I said above, I would be most
>happy to pay for an answer if that is appropriate.  I've culled such
>excellent real-life advice from other colleagues in this forum that I don't
>in the slightest mind paying this time.
>I am especially appreciative of the current on-going discussion regarding
>wall systems.   The question about the best combination of materials for
>walls has elicited responses that are highly thoughtful.  The wall that
>comes out looking like a Japanese wattle wall hit the jack pot for me.
Richard Kadulski Architect
208 - 1280 Seymour St.
Vancouver, B.C.  V6B 3N9
Tel/Fax 604-689-1841
e-mail: kadulski@cyberstore.ca

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