Searching for the Sun
The Ins and Outs of Passive Solar Design
by Mike Kelley
Even in the earliest times humans knew to capture the sun
for heat. Today, we know that solar energy is the most efficient of all
of our energy sources. It heats our oceans and land masses; it heats our
entire planet. Many people think only of photovoltaics (PV) when they
hear the term “solar energy.” PV is an exciting and promising technology
that has resulted in billions of dollars in investments, as well as some
famous failures. By garnering high amounts of media attention PV has caused
a lot of confusion and has pushed the most basic forms of solar energy
into the shadows. Pun intended.
Some of us in the glass industry are involved with PV, but almost all
of us are involved with solar energy. There are few glazing applications
that do not allow solar lighting or solar heat. Many of our customers
rely on our suggestions to make the best use of solar energy. People do
not like to work or live in caves and it is our role to show them the
importance of glass in energy efficiencies.
The technology to which I am referring is called passive
solar or climate design. With this type of design technique, there isn’t
a specific product to install or sell; that’s why there is no lobby, no
advertising and no funding subsidies. However, residences that were built
in the 1970s with this design tactic in mind are still enjoying its benefits
and will as long as the sun shines.
The most beautiful aspect of passive solar design is that it is mostly
common sense. Some questions commonly asked about passive solar include:
• How can you get heat in the winter and not in the summer?
• How can you eliminate heat from electric lighting, without gaining heat
from the windows?
• Can you overheat some areas to store heat for cold nights
• How can you use the daily movement of the sun to control lighting and
heating of the structure?
• How can you use seasonal movement of the sun to control lighting and
heating of the structure?
Solutions and Answers
The most common structure for passive solar is a highly energy-efficient
residential structure. Many are built into a hill for the north elevation
and are two stories of glass on the southern elevation. There would be
a small amount of glazing on the east and west to provide daylight. One
of the goals of this type of construction is minimizing electric lighting.
The rooftop eave would extend far enough over the glazing so there is
no direct sun in the summer, but maximum direct sun in the winter. In
addition, deciduous trees would protect the glazing areas from direct
sun until they lose their leaves in autumn. It is also possible to achieve
the same shading from screens, movable awnings and the new electrically
activated films. The local climate would dictate the performance levels
of the glazing and windows. However, natural cooling through operating
windows should be a major consideration in any climate.
The interior is important as well. Some might use water-filled
columns to store heat for the night. Sometimes an effective siphon can
be set up so that the heavier, cooler air will flow to the sleeping areas
and the lighter warm air will rise to the highest level for easy ventilation
with an automatic mechanical vent window such as the kind they used in
Passive solar is not a one-product solution that can be
ordered online. Every structure, every latitude and orientation to the
sun requires different techniques that can only be provided by experienced
and well-trained professionals.
Though it may not be the most frequently used design method,
passive solar will never go away and will never become obsolete. I expect
that those who embrace it and employ it will always be in demand.
Mike Kelley manages special projects for TriStar
Glass in Catoosa, Okla. His column appears bi-monthly.
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