By today’s standards, it’s a modest house: three bedrooms, single level, architecturally suited to the late-1960s-era neighborhood in which it sits. Even after just a few months, and thanks in part to the preservation of the mature landscape around it, neighbors tend to forget what the previous house on the lot looked like—a sure sign that the new dwelling is fitting in just fine.
But unlike any other house in Lewisville, Texas, and only a few nationwide, this 2,500-square-foot home is designed and built to achieve net-zero energy consumption. An array of 42 photovoltaic panels along the south-facing roof, hidden from street view, is set to gather and convert enough solar power into electricity to equally offset even the most extreme cooling loads and the rest of the home’s power needs, with a little extra capacity built in to earn some extra net-metering credits from the local utility. Ideally, the only line item on the homeowner’s monthly energy bill will be the service charge to keep the account open.
Still, the 600-square-foot PV array is only the mechanism for balancing the home’s power draw, not its defining feature. “This is a high-performance house with some green products in it,” says Chris Miles, a principal with GreenCraft Builders in Lewisville and a student of building science. “You don’t need green products for a house to perform well, but homeowners like it and I enjoy integrating them into the houses we build.”
That mix of passion and market savvy has enabled Miles to build seven homes to LEED-Gold or higher certification. This latest one reaches the Platinum level of that rating system (with a HERS score of 1, among other feats) and meets the standards for the Energy Star Qualified Homes and Green Built Texas programs (the latter of which is awarded automatically to homes that achieve at least LEED for Homes Silver); certification under the ANSI National Green Building Standard is pending.
Even after collecting all that hardware, the builder is only impressed with how his homes actually perform. That’s why, after discovering and diving head first into building science five years ago, Miles became a Building America builder, dedicated to reducing the carbon footprint of the built world under the guidelines of that Department of Energy program. “They come in and test for everything,” he says of the Building America verifiers who use homes like his to expand their database of real-world applications and results. “It’s the only way we really know how to improve what we do.”
That testing came in handy when Miles and architect Bill Peck considered the challenge of a net-zero house. “There’s no way of knowing if you have enough PVs unless you know how much energy the house will require,” a calculation based on its design, construction, and everyday occupant behavior, says Miles.
Results from monitoring the energy demand of a 2,400-square-foot, single-story, high-performance house Miles built two years ago, his first show home with GreenCraft, proved invaluable for this latest project, helping drive the home’s orientation and layout to accommodate an array that would generate 1,000 kWh of electricity to offset an anticipated draw of 805 kWh a year. “We didn’t have to guess on this one,” says the builder.
Even if net-zero hadn’t been the goal, Peck says he still would have oriented the house the same way, primarily along a north-south axis instead of the east-west exposure the previous homeowners endured. “We maintained the west-facing street presence of the original house (and its setbacks, per local ordinance—another reason the new house fits in so well), but the main living areas are oriented the opposite way,” he says, to achieve a more comfortable indoor environment.
To shield the new south-facing elevation, Peck designed deep roof overhangs, including a flat section extending from the gable roof eaves of the living room, and added an extensive deck with a trellised roof; the deck also corrals an existing mature tree on the property that provides another measure of shade. On the west side, Peck designed custom-fabricated sunshades for the bedroom windows that mimic the standing-seam metal roof and add to the dimension of that elevation.
High-performance, fiberglass-framed casement and awning-style clerestory windows help mitigate solar heat gain, as well, thanks to an NFRC-certified 0.23 solar heat gain coefficient; by design and placement, the windows also capture prevailing breezes and vent hot air for passive cooling. And, with a visual light transmittance of 52%, they allow ample natural light into and through the narrow building footprint.
“[Some people] give us a hard time about how many windows we use in an energy-efficient house,” says Peck, noting that the ratio in his designs is often about 20% of the total wall area, a third more than what’s considered conventional. “But if you have enough natural light, you don’t need to turn on the lights during the day and the spaces are more livable.”
With the comfort of his homeowners a priority, Miles recently committed to integrating finish products that reduce indoor pollutant sources. “When you build this tight, you have to consider your finishes,” he says, referring to their off-gassing of volatile organic compounds (VOCs). To that end, he specified and applied low-VOC paints and adhesives, and cabinets and other woodwork with formaldehyde-free MDF; he also completely eschewed finished flooring, instead gaining the owner’s support for a stained concrete floor throughout.
That floor combines with reclaimed brick from a south Dallas warehouse, engineered decking, fiber-cement siding, the metal roof, quartz surfacing, and stone accents for a relatively hassle-free maintenance list for the owners—and another aspect of the home’s overall sustainability. Even the PV panels, solar thermal collectors, and rainwater collection and irrigation system feature few moving parts, making them easier to troubleshoot, if necessary.
From the beginning of the project, Miles educated the owners about optimizing the efficiencies of their new home, including their selection of a television (plasma bad; LCD good), turning off lights in unoccupied rooms, and unplugging cable boxes and other devices at night.
The impact of a wasteful lifestyle on the energy bill is driven home, Miles says, when the owners watch the meters that Building America uses to track the consumption of the heating and cooling system and see that their behavior, not the A/C, is what’s boosting power demand. “Once they realize that, they start making some changes.”
Fortunately, the owners were savvy to Miles’ methods. “It all made sense to them from the beginning,” says Peck, who first worked with the owners to try and remodel the original house before finding extensive structural damage that required a teardown. “Their learning curve was very short.”
Rich Binsacca is a contributing editor for EcoHome.
PROFILE: Chris Miles
GREENCRAFT BUILDERS, LEWISVILLE, TEXAS
Chris Miles, GreenCraft Builders, Lewisville, Texas
Chris Miles’ drive to reduce the carbon footprint of the built environment is tireless. While he finished a LEED-Platinum custom spec house last March, just in time for tours during the NAHB National Green Building Conference, he and architect Bill Peck began a zero-energy house with a 14-week construction schedule, this time with a homeowner already attached. “We weren’t going to do a second show house this year,” Miles says, “but in a down year we were afraid we’d lose our sponsors if we didn’t jump on it.”
Sponsors are just one anomaly of Miles’ homes and his history. For nearly 15 years every Saturday afternoon, for instance, he’s hosted HouseTalk, a radio show advocating building science and energy efficiency, among other things, to consumers and pros in North Texas.
And while Miles subjects his homes to various green certification standards, he resents manufacturers and suppliers who push green products as a way to gain rating-systems credits. “That’s not why I use a particular product or how I want my business to be known,” he says. “I use something because it’s good for the house, to enhance its comfort and quality, not to get a bunch of points.”
What does excite him about LEED and other programs are the provisions and requirements for using local and regional sources, reclaimed and recycled-content products, water-conservation and reclamation systems, and construction waste management tactics. “Learning about ways to meet those specifications is what’s fun about what we do.” —R.B.