low energy building design
Choose the
H
PV may be the sexy strategy,
but solar-responsive design is
cheaper and, by reducing a
building’s energy consumption,
more sustainable.
By norber T M. LecHner
norbert M. Lechner ( lechnnm@auburn.edu) is an
architect, professor emeritus in the College of Architecture, Design, and Construction at Auburn University, LEED-accredited professional and ASES Fellow.
He is an expert in energy-responsive architectural
design with an emphasis on solar-responsive design.
Lechner’s book, Heating, Cooling, Lighting: Design
Methods for Architects, is used by more than a third
of all architecture schools in the United States and in
architecture schools worldwide. He is also a sought-after speaker, giving keynote lectures and workshops
at universities and conferences around the world.
For most people, “solar energy” invokes the technologies of photovoltaics (Pv) and, more generally, active solar systems that use electrical or mechanical systems,
like most solar water-heating systems. Unfortunately, these strategies are “high-hanging fruit” in
that they are expensive ways to enjoy the on-site,
pollution-free benefits of solar energy. Should
we not first pick the low-hanging fruit, such as
passive solar techniques?
taking a “Free Lunch”
Although not always recognized as such, the
following strategies are all directly solar: the form
and orientation of a building; the size, number
and location of windows; the solar heat gain
coefficient of the glazing; daylighting; shading;
the landscaping around a building; green roofs
and walls; and the color of the roof and walls. All
of these strategies utilize solar-responsive design
to reduce the energy consumption of buildings. These are the low-hanging fruit (figure 1).
Although some of these strategies do not collect
solar energy, they save energy by designing with
PV (photovoltaics)
Active Solar
Daylighting
Window Size
Window
Placement
Building
Orientation
the sun in mind. Just as a dollar saved is a dollar earned, energy saved is equivalent to energy
produced. not only is it cheaper to save energy,
it is also much more sustainable.
Some of these low-hanging-fruit strategies are
a “free lunch,” in that they cost nothing and yet
save much energy. Some are even what Amory
Lovins has called, “better than a free lunch, it’s
a lunch you get paid to eat,” in that they save
energy while reducing the initial cost of the
building. For example, rotating a certain building 90 degrees during the design stage can not
only save up to 50 percent of the energy needed
for heating, cooling and lighting, but it can also
lower the initial cost because the size of the cooling system can be reduced (figure 2).
Though not usually free, a strategy that is
usually cost-effective is shading. It may well be
the solar strategy with the most benefit now and
in the near future because shading can greatly
reduce the energy consumed by air-conditioning
systems. mechanical cooling is no longer limited
to developed countries — it is widely used in
china, Southeast Asia and increasingly in India.
Passive Solar
Shading
Building
Color
Figure 1: When it comes to solar energy
strategies, sustainability is most advanced
by picking the “low-hanging fruit” first,
