Woodstock home features the latest in passive house design


Daniel Levy (photos by Dion Ogust)

Contrary to popular wisdom, says Daniel Levy of Greenspring Building Systems, “Houses don’t need to breathe. When your house breathes, you’re heating or cooling the outdoors.”

We’re standing in the utility room of his Woodstock home, built according to passive house standards that have been widely embraced in Europe as a means of reducing fossil fuel emissions. Overhead is a heat-exchange box connected to four insulated tube-like air ducts.

Inside the box, explains Levy, air arriving from outdoors passes through a filter to remove dust and allergens before it’s sent to living spaces in the house. At the same time, the temperature of the incoming air is raised or lowered through proximity to a compartment of exhaust air from the kitchen and bathrooms, passing through the box on its way out of the house. The heat exchange, combined with super-insulated walls and roof, an airtight building envelope, and a low-energy electric heat pump system, keeps the house at a constant temperature with minimal expenditure of energy, no fossil fuels, and low utility bills.


Levy’s home is the second certified passive house in the U.S. to be built with autoclaved aerated concrete (AAC), a lightweight, highly insulating, fire-resistant, insect-resistant, mold-resistant building material. Three more AAC buildings on Staten Island are nearing certification as part of a study to demonstrate the resilience of the material in flood events. According to Aercon, the only U.S. manufacturer of AAC, the substance is made from quartzite sand, lime, water, cement, and a rising agent, such as aluminum powder — not so different from the baking powder that adds bubbles of air to your cake in the oven. Aercon states that the ingredients are all natural and can be broken down and recycled when necessary. The steam-curing process that is used to bake the blocks is said to have low environmental impact.

Levy sandwiched his AAC with plaster on the inside and six inches of mineral wool insulation, covered by fiber cement siding, on the outside. The blocks, which contain air pockets, are so light, his then 12-year-old son was able to help with construction when Levy used them for a project in Baltimore.

AAC was invented in Sweden in 1924. There are now over 300 factories worldwide, and many buildings in Europe have been made with the product. In the U.S., it’s been slow to catch on, as has the passive house concept (not to be confused with the passive solar concept). Levy believes our slowness to adopt sustainable technologies is due to the country’s heavy investment to oil. “In Europe, they jumped on it,” he said. “Here, we go to war to keep oil prices down.”

“When Europeans come here, we’re a third-world country in terms of housing standards,” agrees Tina Lieberman, Levy’s life partner and education chair for the Sierra Club’s Hudson-Mohawk Group. But U.S. interest is slowly growing. Lieberman recently attended a public meeting of the Hudson Valley chapter of the Passive House Alliance, which featured presentations by architects, city planners, and builders. A representative of NYSERDA, the New York State Energy Research and Development Authority, reported on a recent trip to the Netherlands to study the use of passive house technology. NYSERDA offers rebates for construction that successfully combines passive house design with solar power to produce more energy than it uses — the grail of net-zero energy.

“When they say renewable sources will never meet our energy needs,” remarks Levy, “I say, reduce the amount of energy we need by building more efficient buildings, and we’ll be able to supply it with renewables. A lot of people put up big solar arrays, but they don’t address the energy use of the building.” He considers passive house design more efficient and much cheaper than geothermal  technology, which pulls heat out of the ground — especially in the cold Northeast.

Passive design has been applied to buildings other than homes, including dormitories, factories, and low-rise apartments. In fact, it’s more cost-effective in larger structures because of their lower ratio of surface area to volume. The cost of building with passive technology has been estimated at zero to 25 percent higher than traditional building designs, but that increase is offset by the reduction in energy costs. Habitat for Humanity has been building passive homes across the country as affordable housing, given that low-income families tend to use up to 40 percent of their income on utility bills. The organization built a set of passive-design townhouses in Hudson in 2013.

At Levy’s house, the outdoor heat pump provides heating, cooling, and dehumidification through small indoor ductless “mini-split” wall-mounted units, like the ones installed in recent years at the Golden Notebook in Woodstock and the Phoenicia Library. Levy’s water heater and clothes dryer are both run by the heat pump. All windows and doors are triple-glazed. Solar panels on the south-facing roof have been sending energy back to the grid all summer, and Levy is starting to draw on his built-up credit with the power company to run the heat pump in the cold season. So far, he has not had to pay for power, aside from the $24 monthly fee just to have an account.

Levy, who also restores buildings, says it’s possible to retrofit homes with passive design. He’s excited by the technology and is constantly measuring its effectiveness in his own home, which has been certified, through stringent testing and study, by the Passive House Institute U.S. (PHIUS). Levy himself is certified as a passive house builder through PHIUS. “I’d love to build a row of townhouses or a community of zero-emissions homes that are also low-maintenance,” he says. “We could pull in permaculture folks to produce food year-round. I’m looking to collaborate.”

He rents out one of his upstairs bedrooms on Airbnb, and he says the guests are impressed by the quality of the house. The only problem is the tendency of renters to open the bedroom windows, diminishing the benefits of the carefully calibrated ventilation system by admitting humidity and unconditioned air. “Some people complain they want the smells and sounds of nature,” said Levy. “I think you should go outdoors for that, so I built a screened-in porch.”

On the other hand, he pointed to an ultra-thin layer of dust on the dresser. I wiped it with my finger, and the dust barely coated my skin. “I haven’t dusted since I moved in,” he said, “and that was seven months ago.” Now there’s a plus!

For more information on passive house design, or to contact Daniel Levy, visit http://www.greenspringbuildingsystems.com.