Habitat Chapter Sees an Energy-Efficient Future
An upstate New York chapter of Habitat for Humanity starts with Energy Star building and decides to up its game to the Passivhaus standard
An upstate New York Habitat for Humanity chapter was already committed to energy-efficient design when it began mulling over the possibility of a project built to the PassivhausA residential building construction standard requiring very low levels of air leakage, very high levels of insulation, and windows with a very low U-factor. Developed in the early 1990s by Bo Adamson and Wolfgang Feist, the standard is now promoted by the Passivhaus Institut in Darmstadt, Germany. To meet the standard, a home must have an infiltration rate no greater than 0.60 AC/H @ 50 pascals, a maximum annual heating energy use of 15 kWh per square meter (4,755 Btu per square foot), a maximum annual cooling energy use of 15 kWh per square meter (1.39 kWh per square foot), and maximum source energy use for all purposes of 120 kWh per square meter (11.1 kWh per square foot). The standard recommends, but does not require, a maximum design heating load of 10 W per square meter and windows with a maximum U-factor of 0.14. The Passivhaus standard was developed for buildings in central and northern Europe; efforts are underway to clarify the best techniques to achieve the standard for buildings in hot climates. standard — maybe not right away, mind you, but some time in the future. Then executive director Brenda Adams ran into a celebrated architect who had just wrapped up his first Passivhaus project. "What are you waiting for?" he asked her.
The result of the ensuing collaboration between the Columbia County Habitat chapter in Hudson, New York, and architect Dennis Wedlick and his firm was a two-unit town house. It didn't quite meet requirements for Passivhaus certfication, but Adams is convinced that energy-efficient design is the future of affordable housing, and the chapter already has broken ground on its second Passivhaus project. A third is in the pipeline for next year.
Adams said that Habitat had been drawn to the Passivhaus standard because the standard had the potential to overcome one of the principal challenges to home ownership for people who don't earn a lot of money: high energy costs. Wedlick, whose firm BarlisWedlick has offices in both Hudson and New York City, had recently completed the state's first Passivhaus project, and his nudge was all it took.
Wedlick and his partner Alan Barlis donated their services, and together they worked with the Habitat chapter to plan the project.
It was a "tremendously positive experience," Adams said.
Close but no cigar on certification
The 1,200-square-foot Hudson townhouses (1,614 square feet each if the conditioned basements are included) have double stud exterior walls that are insulated to R-42 with blown-in cellulose. The main roof is trussed; it is insulated to R-87. The slab is insulated to R-56.
This year's project, Adams said, is a hybrid that combines stick construction with structural insulated panels (SIPs). Next year's project will be an all-SIP design.
Habitat's real goal, she said, is the development of a template for affordable housing that can deliver predictable results.
Columbia County (population, 60,000) is south of the New York capital on the Hudson River. The chapter now builds two houses per year, although Adams said she hoped that number would grow in the future.
The townhouse project was a "small but mighty" first step. Adams said that the building's performance has been measured since completion. Adams said the townhouses performed better than planners had expected despite a cold winter.
But Passivhaus certification was not in the cards. The project just squeaked by on the blower-door testTest used to determine a home’s airtightness: a powerful fan is mounted in an exterior door opening and used to pressurize or depressurize the house. By measuring the force needed to maintain a certain pressure difference, a measure of the home’s airtightness can be determined. Operating the blower door also exaggerates air leakage and permits a weatherization contractor to find and seal those leakage areas. for air-tightness, at 0.59 air changes per hour at a pressure difference of 50 pascals (the limit is 0.6 ach50). But air-flow problems with the ventilation system prevented the project from meeting all of the certification requirements, according to Jordan Dentz of the The Levy Partnership, which did field testing on the project. Levy Partnership also donated its time.
Other project details
Each three-bedroom, 1 1/2-bath townhouse cost about $125,000 and required 4,000 hours of volunteer labor, according to an article about the project in Builder. Money to build the units came from a variety of sources. The city of Hudson donated the infill lot.
Other details, as provided by Barlis/Wedlick and The Levy Partnership:
- Domestic hot water: Electric storage tank model.
- Heating and cooling: One ductless minisplit heat pumpHeating and cooling system in which specialized refrigerant fluid in a sealed system is alternately evaporated and condensed, changing its state from liquid to vapor by altering its pressure; this phase change allows heat to be transferred into or out of the house. See air-source heat pump and ground-source heat pump. per side unit.
- Windows: triple-glazed Intus units with solar heat gainIncrease in the amount of heat in a space, including heat transferred from outside (in the form of solar radiation) and heat generated within by people, lights, mechanical systems, and other sources. See heat loss. coefficients ranging from 0.37 to 0.62 and center-of-glass U-factors ranging from 0.09 to 0.123.
Habitat chapters around the country make their own decisions about the projects they undertake. A relatively small number of them have decided to build high-performance housing, either net-zero energyProducing as much energy on an annual basis as one consumes on site, usually with renewable energy sources such as photovoltaics or small-scale wind turbines. or Passivhaus, but about three-quarters of all new Habitat housing meets Energy StarLabeling system sponsored by the Environmental Protection Agency and the US Department of Energy for labeling the most energy-efficient products on the market; applies to a wide range of products, from computers and office equipment to refrigerators and air conditioners. guidelines.
- BarlisWedlick Architects