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While effective passive solar design is highly climate-specific, in most moderate climate zones the overall intention generally includes collecting, storing and distributing solar energy during the winter months and shielding the home from the sun in the summer. This can include large south- and west-facing windows to allow more lower-angle sunlight to penetrate the home during the winter, and using sun shades, awnings, insulated blinds and trellises to help block the hot summer sun.

Generally, these strategies are nontechnical and can be incorporated at minimal cost. However, considering the potential energy savings that these designs can bring, passive solar “represents the smartest and most economical approach that architects and builders can employ in terms of creating energy-efficient homes,” says Dave Kreutzman, CEO of Next Generation Energy, a solar research and manufacturing company. “A home can be equipped with a state-of-the-art solar system, but without a smart design it will not be energy-efficient,” he says. “This is where integration is important. The home’s orientation, window design, shading, thermal mass, and ventilation need to be correctly integrated in order to achieve a low-energy solution.”

Passive solar design can also be an excellent partner with active solar technology, but it needs to be applied intelligently in order to achieve better energy savings, says Gordon Handelsman, co-founder and CMO of solar company EchoFirst Inc. “The design concept behind passive solar is relatively straightforward but it is not a one-size-fits-all approach,” he says. “The regional climate, the seasonal calendar, and the specific building location all need to be taken into account and factored correctly.”

In extreme climates, passive solar strategies take on even greater significance. Ed Gorman, president of Phoenix-based Modus Development, says in the Arizona desert it is highly important to respect the heat that is imparted by the sun. “We take great care in orienting our buildings to take advantage of passive solar design—improper orientation can increase cooling costs, create glare and make interior spaces uncomfortable,” he says.

All of the units in Gorman’s The Galleries at Turney condominium project were oriented so that they faced due north and south and included large expanses of glass on the south-facing sides to allow a significant amount of light into the homes, virtually eliminating the need for daytime lighting. “The locations for these windows were chosen carefully to minimize solar gain, Gorman says. “The large window walls were recessed 5 feet from the edge of the building to provide shading in the summer, yet allow in the sun during the winter months.”

“Passive-designed homes should have enough thermal mass for energy absorption and prolonged dispersal,” says Milos Jovanovic, co-founder of Portland, OR-based Root Design Build. “Masonry elements provide great ‘heat sinks,’ and adding tile or concrete flooring in front of windows is an ideal way to add thermal mass. Another easy way to beef up thermal mass includes doubling up on drywall on the interior walls and ceiling. Gypsum is a heavy material that easily absorbs heat and provides added thermal mass.”

Windows—the weakest points of the thermal envelope—are a critical focus area in passive solar design. Depending on the climate, several factors in window design need to be considered, including orientation, size, glazing and thermal performance. “The latest building research shows us that we need to strike a balance between the thermal performance and the amount of heat and light that windows admit,” Jovanovic says. “In the past, one of the problems in passive solar design included south-facing windows with too much glazing. Aside from overheating in the summer, heat would tend to escape through the glass during the night.”

More building designs for promoting passive solar heating include sunspaces or solar rooms, which are built on the south side of a home and function similarly to a greenhouse, promoting isolated solar heat gain. Trombe walls, also located on the south-facing side of a home, consist of a thick, dark colored wall with a sheet of glass mounted a few inches from the surface. After absorbing heat throughout the day, the wall slowly releases the heat into the living space during the night. New innovative solutions are also being combined with active solar technology to harness more energy. EchoFirst Inc. has developed an ultra-efficient solar PV panel system that features a solar thermal application that works by capturing and utilizing waste heat from the panels, which in turn can be used toward water heating and home heating or cooling.

Next Generation Energy, in addition to manufacturing solar PV and solar thermal systems, also offers thermosiphon systems, a passive method for heating water that involves a storage tank located above a solar panel. By way of gravity and natural convection, water is circulated through the panels and heated. “Another economical way to incorporate passive solar includes solar skylights, which allow more light and heat energy into the home while also reducing the need to use electricity for lighting,” Kreutzman says.

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