The Passive House: Built for Energy Savings

By Katherine Salant

Unusally energy-efficient Passive House in Bethesda, Maryland by architect David Peabody uses 90 percent less energy for heating and cooling than a comparably-sized conventionally built house. Photo Credit: Jim Tetro Architectural Photography

The casual passerby in Ian and Lydia Kline’s neighborhood in Bethesda, Maryland, would notice that their clapboard-sided, four-square Craftsman-styled house stands out from the 1930s and ‘40s brick-sided Cape Cods that line their street.

The more astute observer would note the pristine condition of the Klines’ house and correctly surmise that it is the newest one on the block.

The visitor invited inside would be immediately taken with the well-proportioned, sunlit spaces and the clever update of an American classic designed by Alexandria, Virginia, architect David Peabody. Unlike the four-squares of 100 years ago that were chopped up into small and very separate rooms, Peabody’s version is very open, with each quadrant defined by strategically placed closets and columns and ceiling treatment, not walls. In the Klines’ house, the person fixing dinner in the kitchen is not shut off from the activity in the adjacent living and dining areas and entry foyer.

But few of the Klines’ visitors will note the detail that marks their house as unique in the Washington, D.C., area and one of only four in the entire Mid-Atlantic region. That detail would be the 7-inch deep window sills and deep-set windows that reveal the unusually thick 9-inch walls.

The Kline’s house was built to the Passive House Institute US standard, and it consumes 90 percent less energy for heating and cooling compared with a conventionally built house of similar size, Peabody said.

Germany to America
The Passive House concept was first developed in Germany about 20 years ago as a way to drastically reduce the cost of home heating by minimizing the amount of heat required. A Passive House achieves this with its unusually thick, well-insulated walls and roof and a near obsessive plugging up of all air leaks during construction. The first Passive House in the U.S. was built in Urbana, Illinois, in 2003. Karen Klingenberg, who heads up the Passive House Institute US, said that by the end of 2013 her organization will have certified more than 100 houses. The Klines’ house, which was completed in July of 2011, was the 23rd.

Peabody said he was initially drawn to the Passive House approach because “it promised energy efficiency that was both astounding and affordable, and energy efficiency is the name of the game for climate issues.” In the U.S., building energy use is the biggest source of the greenhouse gas emissions that are causing global warming.

Peabody said he was also drawn to the simplicity of both the Passive House concept and its execution. A Passive House is basically a super-insulated box, and its extreme energy efficiency is achievable with readily available, off-the-shelf parts. “No pricey space-age technology is required!” he said.

But, Peabody realized, to build a house to the Passive House standard and get it certified by the Passive House Institute US, he had to work with a home builder who would be open to very different construction techniques and a mechanical engineer who could design a heating and cooling system that could deliver a high level of comfort in Washington’s cold winters and humid summers with a minimum expenditure of energy. Peabody teamed up with two Maryland professionals, Brendan O’Neill Jr. of O’Neill Development, a Gaithersburg firm known for innovation, and Dan Foley, a Lorton-based mechanical engineer.

Peabody based his design on a traditional four-square house because its simple box shape maximizes the interior volume while minimizing the area of its exterior envelope and potential heat loss.

Building with SIPS
The building envelope of Peabody’s Passive House is made of structural insulated panels, commonly called SIPS, rather than the “stick built” wood framing that is common in the Washington area. Each SIPS panel has a foam core sandwiched between two sheets of oriented strand board. To achieve the desired level of insulation, the SIPS wall panels are 7 inches thick; another 2 inches of rigid foam insulation was added to their exterior side. The SIPS roof panels are 12 inches thick. The casement windows have three layers of glass and the window frames are also insulated. Lydia Kline said that when you look out, you can’t tell you’re peering through three panes of glass; if anything, she said, the view is clearer.

Heating, cooling, saving
Peabody said the most challenging part of the project was the heating and cooling system. Because the building envelope is so tight, fresh air is brought in mechanically; about half the air in the house is replaced every hour. To minimize the amount of energy required to heat or cool all this incoming air, the team used a low-tech, low-energy system that tempers the incoming air — it heats it up or cools it down, depending on the season — before it passes into the house. Once inside, only a minimal energy draw from the heating and cooling system is needed to bring the incoming air to the desired room temperature. Attesting to its performance, Foley said he’s been in the house when the outside temperature was over 100 degrees Fahrenheit and the interior was a comfortable 74 degrees.

The energy-saving aspect of the house appealed to the Klines because Ian Kline is an energy consultant who monitors energy usage in commercial and industrial buildings and, he said, “I wanted a residential application of what we pursue as a firm.” But both Klines said the bigger draw was the ambiance of the house. Though it’s brand-new construction and Craftsman-styled, it feels like the 1870 Boston-area Victorian they lived in before moving to the Washington area.

With the heavily insulated walls, Lydia Kline noted, the house is incredibly quiet inside. So quiet that during last fall’s Hurricane Sandy, “you had to look outside to know there was a storm,” she said.

The Klines said their utility bills average about $200 a month, despite the 4,400-square-foot size of their house. Such a low amount for such a big house impresses those who ask, though Ian Kline said he isn’t sure that people find it credible. “People hear these numbers and say they sound amazing, but I’m not sure everyone believes the numbers,” he said.

The features that reduced the Klines’ household energy for heating and cooling by 90 percent added about 6 to 8 percent to its construction cost, O’Neill said. For this house, which sold for $1.4 million, the added cost was about $55,000.00. At this price point, O’Neill noted, the added cost was not a deal breaker.

O’Neill anticipates that the added cost of the energy-saving features will go down as he builds more Passive Houses and their unusual construction requirements become routine (he’s building his second one now).

Is the Passive House destined to remain a niche product or does it have mainstream potential? Bob Hubbell, president of Brookfield Homes Washington, D.C., Metro Area Division, said that today’s production home buyers still favor glitz and glamour over energy-saving features. But, he said, as building codes require new houses to become ever more energy-efficient, the Passive House might become a feasible option for the mass market. February 2013

Originally Published in Katherinesalant.com

08/06/2014

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