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Project

Bethesda Zero Energy Home (Maryland, USA)

Credits: ©2011 Meditch Murphy Architects

Not far from Washington, D.C., the Bethesda Zero Energy House produces more power than it uses with a rooftop 9.6 kilowatt photovoltaic solar array and its hot water comes from rooftop flat-panel solar hot water collectors. This Maryland green building also uses a geothermal heat pump to heat and cool the home with two 375-foot wells drilled to access the constant ground temperature of about 50 degrees. The solar and geothermal systems could be sized a bit smaller due to the extremely efficient building envelope that is insulated with ultra-tight soy-polyurethane spray foam and rigid polystyrene board insulation. An energy-recovery ventilator transfers moisture from the exhaust air to fresh incoming air. An open floor plan creates better air flow for natural ventilation, and monitoring systems can track indoor humidity, start heating and cooling systems heating with a phone call, and send alerts if conditions go awry. A vegetated roof provides a sort of planted patio above the garage wing, and rainwater is collected into two large tanks on the north side of the house. The home sits in a walkable community, with a community garden, clubhouse, playground, swimming pool, a bus-stop and schools nearby. Green, sustainable materials throughout the home contribute no VOCs. (Scroll to bottom for additional resources)

 

Bethesda Zero Insulation

The architects for the Zero Energy Home in Bethesda, Maryland, specified a layer of insulation on the outside of the house’s framing to act as the first line of defense, with additional foam insulation between the studs. In such a tightly sealed structure, an energy recovery ventilator (ERV) is also used that preconditions the air. ©2010 Anice Hoachlander

The following article is from The Washington Post
By Elizabeth Festa, May 1, 2010

In Bethesda, a home built to have a net-zero carbon footprint
Architect Marcie Meditch set out to show how a highly energy-efficient home could be built for a typical market price in a dense, suburban neighborhood like Bethesda.

So, without a buyer lined up for the house, she and her husband, John Murphey, principals of Meditch Murphey Architects in Chevy Chase, designed a "net zero" house, intended to consume only as much energy as it produces. And despite Meditch's fears that it might be difficult to sell once completed, it was snatched off the market in November -- before construction was finished -- for just under $1.8 million.

The buyer, Ann Luskey, a philanthropist who devotes much of her life to ocean conservation and eco-conscious living, found that the house and its neighborhood offered the green lifestyle she was trying to pursue.

After a divorce, Luskey was looking to downsize from an 11,000-square-foot house in McLean. She wanted a home that was "not too excessive," and where she and her three school-age children would be comfortable. She wanted a home that she could make greener over time, and if she could find one that was LEED-certified, a Leadership in Energy and Environmental Design certification awarded by the U.S. Green Building Council, so much the better.

"As I learned more and more about environmentalism and carbon footprints and all these things, [living in a big house in McLean] started feeling over the top and inappropriate," Luskey said.

"I can't believe I found a house close to the canal, the bike path, close to school in a more typical type of neighborhood for my kids so they could bike to their house," she said.

"The neighborhood I came from in McLean is beautiful, is on the Potomac, is exquisite, but the neighbors are far apart. It is hard to get to each other's houses. There are no sidewalks, no paths," she said. The distance between my room [in the net-zero house] and their room is smaller; [it's] more cozy."

The Bethesda house is in a walkable community, with a pool, a bus-stop and schools, while a community clubhouse, playground, daycare center and community garden all nearby.

In the years between their time in McLean and their new home in Bethesda, Luskey and her children have lived aboard a Dutch-built motor yacht, sometimes docked along the Potomac waterfront. Her youngest learned to walk while living aboard the boat, and it's where all the children have been home-schooled while the family sailed around the Caribbean and the Americas.

Luskey said she looked at the carbon footprint of living on the boat and, dividing it among all the friends and staff members who also live onboard, calculated that it amounted to 11,000 pounds of carbon dioxide emissions per person per year, versus the U.S. average of 20,000 pounds, she said.

Gallery on land
When Luskey bought the Bethesda property, the 4,000-square-foot, five-bedroom house was framed, and had exterior sheathing but no drywall and no exterior siding. Electrical and plumbing rough-ins had just been completed.

Meditch said she and her design team simplified the layout so they could put money into green features. The first floor has an open plan and consists of living room, dining room and kitchen, put together as one long room, and the master bedroom and garage are in another wing, forming an L-shaped house.

The price of the house, Meditch said, was "fairly comparable" for the square footage in that neighborhood, nestled between MacArthur Boulevard and Wilson Lane. A nearby home had recently sold for about $1.5 million.

While the house interior was still being finished, Luskey helped outfit it with eco-conscious finds, such as plants for the green roof that were salvaged from the Solar Decathlon held on the Mall in October. The kitchen floor is made of recycled concrete and wood.

"The thing about green construction and green-living designs is it's not a sacrifice," Luskey said. "If you take the time to research different products, you are going to find incredibly beautiful, cool things. If I do a Google on 'green countertops,' I can find 20 products that are LEED-certifiable or green in some form or fashion. About 50 percent are something I like a lot," she said.

Luskey, who has a background as an interior designer, has decorated her home with finds from her world travel. Pygmy headdresses made of brightly dyed chicken feathers are poised high above the sofa and chairs. The gallery-like space holds an enormous blue painting by Hungarian artist Agathe Vaito. The walls are adorned with African fertility statues and masks from her time living in Tanzania.

Energy from sun, Earth
The design calls for all the energy required by the house to be generated onsite by a large 9.6 kilowatt photovoltaic solar array on the roof and flat-panel solar hot water collectors. The design also relies on a WaterFurnace geothermal heat pump to heat and cool the home.

The house was built with ultra-tight insulation from soy-polyurethane spray foam and rigid polystyrene board insulation. An energy-recovery ventilator transfers moisture from the exhaust air to fresh incoming air in the tightly insulated house

Without a good insulation, the solar array would have to be much bigger to meet the home's energy needs, Meditch said, and the open floor plan creates better air flow. Monitoring systems can track indoor humidity, start heating and cooling systems heating with a phone call, and send alerts if conditions go awry.

Green principles dictated the choice of many building materials as well. Walls were built with gypsum wallboard harvested and manufactured within 500 miles of use. Maple flooring was from a sustainable managed forest; the 400- to 500-gallon rain barrels will save water from the downspouts. The landscape is planted with Eco-Lawn by Wildflower Farm, which is slow-growing and drought-tolerant.

A driveway and patio made of pervious concrete allow rainwater to go through to the earth, and the material's light color minimizes heat buildup. The roof is made of "low emissivity" or "cool" roof materials, so it reflects sunlight rather than absorbing its heat.

Colors other than green
"The lighting plan is where I made the most changes in the house," Luskey said. "Marcie wanted to make sure the house could stay in the capacity of the solar panels. As an interior designer, lighting is my thing. . . . I have a certain aesthetic; I like a certain type of fixture, so I changed to a different version of fluorescent. We went to a different fixture that I liked more, then I added more area lighting," she said.

Meditch is eager to see how the house operates with kids running about. Will they remember to extend and retract the hand-crank awnings to control indoor temperatures? Will they leave doors open? Luskey hoped that the required tidiness of boat-living will carry over to life on land.

Meditch plans to apply for LEED Platinum certification, the highest level, after the landscaping, which could increase their score, is finished. Joan Honeyman, of Jordan Honeyman Landscape Architecture, is just finishing the installation of a shade trellis with non-invasive wisteria vines over the south-facing patio to block heat during summer but allow in light during winter.

Having just moved in, Luskey continues to tweak the design. She is not happy with the big, white plastic look of the rain barrels, so they aren't installed, yet; she wants to find a way to bury them so they can operate without detracting from the landscape.

The family's time at sea is not over, though, despite the move to land-based housing. Luskey and her children plan to cruise the Caribbean this summer, assisting marine biologists on various projects. Luskey described their plans as "fun adventures which help the planet -- just like the house! A fun house which helps reduce stress on the planet and its natural resources. . . . .Our children deserve it, the creatures we share the planet with deserve it, and the planet deserves it!!!!!" she wrote in an e-mail.


Documents

  Bethesda Magazine Extreme Green Homes 2009 (699 kb)

  Designing the Zero Energy House (Bethesda, Maryland, USA) (14,543 kb)


Resources

Meditch Murphy Architects (Maryland, USA)