Thursday, July 22, 2010

Betting on Bethesda: The Net Zero Energy House



The Olympics are a memory and few in D.C. are high jumping in the searing summer heat, but in the case of Bethesda Net Zero Energy House, an architect’s leap of faith may surely result in winning the Gold - or even Platinum: LEED Platinum.

“Jimmy Carter had solar panels on the White House,” Meditch Murphey Architects Principal Marcie Meditch recalled, an image which may have fueled her vision from time to time and compelled her to build a 4,000 s.f. net-zero energy “spec” house in Montgomery County’s comfortable, cohesive Bannockburn community. Mulling over the concept for a year or two, concerns about building a market-rate house that was green and had a net zero energy footprint - or used as much energy as it produced - and which would sell in a conservative market had precluded immediate action. “I couldn’t find a client,” Meditch said, recalling the “serendipitous meeting of a friend of a friend” at a conference whose mother had recently passed away. The mother’s mid-century wood frame slab-on-grade house in Bethesda had not aged well and needed to be sold, but the family didn’t want a “McMansion” built on the property in its place.

With siting a key requisite, Meditch recognized the potential and seized the moment for her energy efficient home that would make the best use of the sun, as well as of passive natural energy from water and cross ventilation.

Nature and NASA

“We believe that the best place to start when you’re trying to do energy efficiency is not by conceiving of all the high-tech things, but rather how do you create a house which is thermally efficient, has very efficient walls and proper placement of windows,” said project architect Mike Binder. “If you look at the plan for this house, it’s very simple, for instance the living room windows are right across from each other…so air can flow through the house and cool it naturally rather than having to use mechanical energy. There’s a very strong element of sustainable design that has nothing to do with technology but is more about using what nature provides already,” he said.

Nature withstanding, yet conceding that “nobody lives in this area without air conditioning,” Binder, who was a NASA engineer and literal “rocket scientist” before transitioning to architecture, said a ground source heat pump was designated for the house: two wells planted 375-feet deep that store air at a constant ground temperature of about 50 degrees. In the summer, instead of trying to take the heat from the 78-degree air inside and push it into the 95-degree air outside (a huge expenditure of energy), it is taken from the house and mitigated in the ground. The same principle applies to winter air, where rather than creating heat from the 30-degree air outside, it is culled from its constant 50-degree base in the ground.

With an energy-efficient envelope warranting extreme insulation, Meditch Murphey Architects used a layer of insulation on the outside of the house’s framing to act as the first line of defense. Additional insulation was used between the studs, which Binder explained typically act like a “thermal bridge” for energy loss: energy getting into and out of the house. And with a structure that is essentially sealed the way this one is, an energy recovery ventilator (ERV) preconditions or removes the heat, cold and moisture from the air that’s leaving and puts it into the air that’s entering, according to the seasons, which saves on energy.

Light and Water

On the roof, a flat-panel photovoltaic solar array and flat-panel solar hot water collectors harness and utilize available energy, as does the home’s recirculation loop which uses the cold water supply as a return. “When you turn on the hot water in the bathrooms, unless you’ve got tankless water heaters in each of them, which would be costly, there’s this lag time while you’re waiting,” Binder said, noting all the potable cold water gets flushed down the drain in the meantime. “We take that water and actually put it back into the cold water line, and it goes right back to the hot water heater, so nothing is wasted.”

Where lighting was concerned, a combination of LED lights, halogen and other incandescent types were used in the five-bedroom (one is part of an au pair suite), four-bath home, with halogen used in strategic locations such as bathrooms and the kitchen. “LED’s are still a little cool in their color rendering,” Binder said, noting a more balanced light is important “when you’re looking at your face or when you want to see what color your food really is.” He added that the firm doesn’t subscribe to the tenet of “energy efficiency at the expense of all else, including comfort.”

Wood and Glass

To that end, bathroom features are a confluence of sustainability and aesthetics. Custom vanities were crafted by Ray Amos of Pennsylvania’s New Oxford Studios, whose philosophy mandates using reclaimed lumber. Flooring in much of the home is maple from a sustainably-managed forest, where documents show the trees were harvested without impinging on the ecosystem. In the basement, engineered flooring called Eco Timber, a composite that includes a plywood layer, means the highest quality wood is reserved only for the top where it is visible. In the kitchen, substrate for the cabinets is particle board which, instead of being made with traditional high-VOC binders, has a high recycled wood content that is low-VOC with no formaldehyde added to help promote the home’s indoor air quality.

When the home, not yet finished, sold quickly in the fall of 2009, new homeowner Ann Luskey got involved early enough in the process to choose her own tile for the kitchen and downstairs floors, according to Binder, selecting Ecocem (part cement; part cellulose fiber) which is entirely recycled. Countertops are Eco-Terr, which is cement and polished, recycled glass. “It looks like Terrazzo because of its really beautiful finish,” Binder explained, “but it doesn’t have to be shipped all the way from Italy.”

Earth and Trees

Outside the home, Joan Honeyman of Jordan Honeyman Landscape Architects selected trees endemic to the region that would not require artificial irrigation. The trees, deciduous to open the home’s exterior to the sun in winter, will grow as high as the eaves, and not the solar panels, in order to shade just the house in the warmer months. Eco-Lawn, a drought-tolerant grass which requires no watering once it’s germinated and no fertilizers, was also used. All of the patio areas around the house were constructed with pavers: essentially bricks without grouting around which water can flow into the cracks and soak into the ground. Pervious concrete used for the driveway, which Binder said resembles Rice Krispies, allows water to penetrate through to an underlying gravel bed and ultimately to the ground beneath. A flat roof over the master suite and garage was designed to be green, but the architects weren’t sure they could afford it so took a step back. However Luskey, with a background in design, resourcefully went to the Mall at the end of the 2009 U.S. Department of Energy Solar Decathlon, where 20 collegiate teams had built solar powered homes, and wrangled a green roof destined for the green roof graveyard. “She has maybe half of the area covered. Hopefully some day the house will have a complete green roof,” Binder said, noting the house was designed to be able to evolve easily with its occupants’ needs.


Endorsed by the owner and angling for a LEED Platinum rating, the architects didn’t know until the spring if the grass would come in properly, a prerequisite for the USGBC (U.S. Green Building Council) LEED inspection which is pending this month. During construction, the architects made ample use of government subsidies for energy efficiency such as property and income tax credits and loan programs from the state, which meant that somewhere between 30 and 50 percent of the cost of the home that sold for $1.8 million was defrayed. “They are essential in making these things attractive to people from a financial point of view,” Binder said.

Photography by Anice Hoachlander

3 comments:

Whiteknuckled said...

Hey, great house and very cool thoughts on the design. If all houses in Montgomery County had these features it would be a huge reduction in energy and resource use. I'm definitely in favor.

But let's just end with the "net-zero energy" talk when discussing a home in a location in which residents are going to be driving to absolutely everywhere they need to go. Nobody in Bannockburn/Potomac can walk much of anywhere, and it's silly to be talking about a home like it's not going to use any energy when it's occupants are going to rack up thousands of miles in their cars generating emissions and burning gasoline every year.

Let's pause to consider the possibility that the house without all of the shiny brand new green tech in an older DC/VA/MD neighborhood where you can walk to the store, kids can bike to school, take the bus or the train to work, and generally own fewer cars and use them less if at all might be greener and use less energy overall than the most awesome space-age NASA-certified green house out in the rolling hills of Potomac.

We've got to quit thinking of buildings as isolated islands of energy and emissions use, and consider the transportation ramifications of where they are located. It's all part of the equation.

Thanks for the post. Indeed, a very cool house.

http://maps.google.com/maps?q=bannockburn,+montgomery+county,+md&ie=UTF8&hq=&hnear=Bannockburn,+Potomac,+Montgomery,+Maryland&gl=us&ei=w2ZITKjKLcH48Aaf3vntDg&ved=0CBMQ8gEwAA&ll=38.971121,-77.141275&spn=0.018818,0.038409&t=h&z=15

m meditch said...

We want to give photo credit to Anice Hoachlander for her terrific photos of the Bethesda Net Zero Energy. We appreciate comments from Whiteknuckled and wholeheartedly agree with establishing 'walking communities'. Contrary to your assumption,the location of the house is within walking distance of a daycare center, elementary school, swimming pool, neighborhood community center, neighborhood garden, post office, grocery/convenience store and a bus stop. We did take these issues into account in the selection of this particular site. Admittedly, we can't control the habits of the occupant. We can only present an opportunity to be 'car-less'.

Anonymous said...

They now make electric cars that use no fuel. Zero Emissions. Drive thousands of miles and using no fossil fuels.

 

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