May 01, 2008
by Steven Castle
The Control4 system also operates the Lutron Sivoia shading system over the large windows, and the thermostats. The motorized shades roll down automatically at certain times so rooms don’t get too hot and require air-conditioning, for instance.
Green on Green
Neither green nor high-tech was on deFreitas’ early radar. “I thought energy efficiency was great, but sustainability wasn’t something I focused on,” he says. “We bought this little 1950s house and planned to tear it down. And the AIA [American Institute of Architects] was pushing sustainability, so it was a goal through the membership to reduce greenhouse gases and increase energy efficiency [in the buildings and houses they designed]. Then we learned we could expedite the permit process through the city’s building department if we saved 15 percent in energy usage, and we thought that would be worth doing. We also thought it would be fun to do a modern structure.”
The architect set out to plan his somewhat efficient modern house, thinking it would be difficult, and what he found surprised him. “A lot of what I thought about energy efficiency was totally false. It was much easier to get to 15 percent than I thought, and I wondered how far we could go. We got to 40 percent without any significant sacrifice. Then we decided to build the house as a showcase home with local magazine San Diego Home/Garden Lifestyles and do as much as we could.”
The house was designed to save energy and resources in three ways: with efficient design; efficient insulation, windows and mechanical systems; and efficient technology. Start with the design, or what some call “passive solar,” using the placement and orientation of the house to optimize sunlight for lighting and ventilation from prevailing breezes. The main part of the house rests on an east-west axis, stretching 80 feet and measuring only 18 feet wide, thereby taking advantage of light with huge windows in some areas. Other windows against corners or floors optimize the reflectivity of the light on surfaces perpendicular to the windows. According to deFreitas, you can generate 30 percent more light in a room by placing windows this way. In one case, a 2-foot-tall window comes right off the floor, which helps reflect more light into the room. “We tried to design it so we wouldn’t need lights on during the day,” he says.
The house is only one-room wide, with windows on both sides of each room, and windows at each end create ventilation from the prevailing westerly breezes. This helps cool the house and cut down on air-conditioning costs. In addition, long overhangs on the south side help block the hot summer sun from the windows, also helping to keep the house naturally cool.
This efficient “passive” design cuts down on the amount of energy required for lighting and ventilation simply by precluding its use. In this case, prevention was the best medicine.
Next, deFreitas concentrated on the use of efficient insulation, glass and mechanical systems. Some windows are dual glazed, Low E2 (the E for emissivity), which means there’s a surface between the panes that reflects heat and ultraviolet rays, while trapping any interior heat and preventing it from escaping.
Walls on the hotter south and west sides were built double-wide (2 by 8 inches) to blow in a mixture of glue and efficient formaldehyde-free chipped fiberglass insulation, which deFreitas says is also great for sound control. The floors, too, are green. The lower level’s floor is the home’s cement slab, with a terrazzo finish and containing radiant heating tubes that slowly warm the concrete into a thermal mass. Concrete is a great retainer of heat, releasing it slowly into a space. The cement floors are also a boon to one of the deFreitas’ daughters, who has asthma, which can be aggravated by particles that get trapped in carpeting and then released.
The mechanical systems are where Casa Futura creates its own energy. Two Viessmann solar panels on the roof are used to heat a 90-gallon tank to between 125 and 155 degrees, providing all the home’s hot water needs, as well as the heat for the radiant-floor system on the lower level and a forced-air system upstairs. For the second-floor heat, a heat exchanger taps the heat from the hot water and blows the warm air at a low velocity. If there’s not enough hot water, a Viessmann tankless boiler burns natural gas and is fitted with a catalytic converter to produce cleaner exhaust.
The 24 Kyocera solar photovoltaic (PV) panels on the roof comprise a 4.8-kilowatt system that feeds electricity to the grid and effectively spins the home’s meter backwards during San Diego’s sunny days. DeFreitas can monitor his PV system’s performance on a device from Fronius that’s tied to the inverter, which converts the solar panel’s DC power to the AC used throughout the house. On the small box, he can check how much energy his home is producing and how much carbon dioxide the family didn’t create by burning fossil fuels.
Steven Castle is Electronic House's managing editor. he has been writing about consumer electronics, homes and energy efficiency topics for two decades. He is also the co-founder of GreenTech Advocates