By Marie Caruso
A house recently built in Woodstock, NY, could be the vanguard of the future in zero-energy housing.
Daniel Levy, Ph.D., a former industrial education professor and certified Passive House consultant and builder, has constructed a two-story, 2350 square foot home, built with non-toxic materials while meeting the criteria for “Passive House.” Passive House is generally considered the world’s most stringent building and energy standard.
Passive House (PH) buildings, which are as likely to be commercial structures as homes, save eighty percent or more energy compared to structures built to current codes in the U.S. The name is a less than ideal translation from the German passivhaus, and is often confused with passive solar designs.
The principles of PH construction are superinsulation, thermal-bridge-free (no components that conduct significant heat through the building’s thermal envelope), airtight to minimize energy loss through infiltration, high performance windows and doors, filtered fresh air with energy or heat recovery ventilation, and design which optimizes solar gain. PH building not only saves energy, it has the added benefits of being more durable and comfortable than conventional construction.
Most houses in the U.S. are built with wood, even those meeting PH standards, and chemical foam insulation products are popular. This one is built with autoclaved aerated concrete (AAC) reinforced with steel rebar, insulated with mineral wool on the outside, and clad with fiber cement siding, which looks similar to wood. The exterior walls are 17 inches thick.
AAC is a lightweight pre-cast concrete product which is fire-, water-, pest-, and sound-resistant, and very strong and durable. It can be worked with typical carpentry tools and holds temperature extremely well. Developed in Sweden in 1923 and commonly used in many other countries, it is just starting to gain a foothold in the U.S.
According to Levy, there are now two homes built with AAC in the United States which are certified by the Passive House Institute US (phius.org), and four additional homes are underway in Staten Island, NY. The Woodstock house is the only one which doesn’t use plastic foam insulation products. The AAC Passive Houses under construction on Staten Island are being built to replace buildings destroyed by Hurricane Sandy. These are being constructed with support from the New York State Energy Research and Development Authority, to demonstrate the resilience of AAC to storms as well as energy efficiency.
Levy’s Woodstock house sits on a concrete slab underlain with 10 inches of Foamglas insulation and a thick Stego vapor barrier. The ceiling is insulated with 24 inches of cellulose. The windows are tilt and turn, triple-glazed, imported from Europe.
The siting of the house and overhangs are designed to maximize sun exposure in the winter and minimize it in the summer. It is all electric, with a 7.56 kilowatt system of photovoltaic solar panels on a steel roof. It is on the electric grid, yet on an annual basis these panels should generate as much power as is needed for both this house and a studio apartment above the attached garage. The garage is wired for electric vehicle charging. There is no chimney, as there is no combustion whatsoever.
As the house is airtight, stale air is removed and fresh air provided through an energy recovery ventilation system. Heating and cooling are achieved with a ductless heat pump. The temperature remains even and comfortable in all seasons.
All the appliances meet Energy Star, and lighting is entirely LED. The water heater and dryer operate with heat pumps, which draw heat from the surrounding air. Cooking is done by induction and baking by convection.
In addition to being certified by Passive House Institute US (PHIUS), the house meets the US Department of Energy Zero Energy Ready Home, NY State Energy Star, Indoor Air Plus, and Water Sense programs.
Levy is passionate about this method of construction and is planning smaller, more moderately priced homes built to the same Passive House, chemical-free standards as this one. If you’d like to learn more about the features of this house and his building techniques, you can reach Levy through his website: GreenspringBuildingSystems.com.
A shorter version of this article was originally published in the summer 2016 issue of “Fresh Air,” the newsletter of the Atlantic Chapter Mid-Hudson Group Sierra Club. Marie Caruso has been an active member of that group since 1979, having previously served as Group Chair, Executive Committee Member, and currently, as Volunteer Coordinator. As a leader in the fights to preserve Lake Minnewaska in the Shawangunk Mountains and Williams Lake in Rosendale, NY, she has written extensively about those issues.