Volume 48, Issue 9- September 2013


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.

Other Options
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.

Common sense
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 green houses.

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.

© Copyright 2013 Key Communications Inc. All rights reserved.
No reproduction of any type without expressed written permission.