||8/26/1999 1:44:00 PM
Your one story choice has an energy penalty. Two
stories that are near square (round is best) will give
you the option of gravity fed air circulation. The
gravity fed system will save about $35 per month blower
energy. A vertical trunk line for your air ducts needs
to be 23 feet high to get circulation as good as most
fans in forced air systems.
This means that in addition to a second story, you will
need at least a partial basement to get that height. An
evaporative cooler at the top will also cool without a
Air filters to collect pollen and dust will work in
a well designed gravity fed system. Gravity fed
furnaces are nothing more than 2 or 3 fanless wall
furnaces facing each other at the basement level. Cool
air ducts under the basement floor bring air to be
heated from the coldest parts of the basement to the
floor of the vertical trunk line. A service door is at
the same level as the furnaces.
The round or square two story approach optimizes
the roof to wall ratio and square footage of the
building's shell. Customizations that sprawl out the
periphery are penalties that can easily rob an extra
25% of wall loss BTU's.
If heating or cooling demand load is small, it may be
desirable to have a small fan in the vertical trunk
line to help the low gravity forces.
||Partnership for Advancing
Technology in Housing (PATH)
451 7th Street, SW, Rm. 8134
Washington, DC 20410-0001
Telephone: 202 708-4370 Fax: 202 708-5873