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As awareness of the emissions associated with materials and construction grows, architects take a more holistic approach to meeting complex sustainable building standards.
FOR MORE than 30 years, Passive House principles have been a valuable guide to making buildings energy efficient. But now, with steady improvements in our understanding of embodied carbon-the carbon emitted when building materials are created, transported, and installed-the overall carbon impact of Passive House construction has become a subject of concern.
Just how much energy does it take to make the added insulation, extra layers of glazing, and other features required to meet Passive House standards, compared to how much energy those features might save over time? "A decade ago, we would talk about the tremendous benefits of operationalenergy savings," says Alan Barlis, a principal at BarlisWedlick, a New York-based firm that has completed about 25 certified Passive House buildings. "Today we tell the rest of the story, and a big part of that story is embodied carbon."
A particular concern is that the large amount of carbon emitted by spray-foam insulation, which is used in some Passive House buildings, will cancel out the expected operational-energy savings. But proponents of Passive House standards say there are many other kinds of insulation, and that Passive House buildings need not be high in embodied carbon. Bronwyn Barry, a San Francisco architect who works pro bono as the policy lead for the New York-based Passive House Network (until recently called the North American Passive House Network), says, "We're starting to pay close attention to embodied carbon. What we've seen from our early studies is that the choices homeowners make about things like square footage have a greater impact on embodied carbon than the decision to follow Passive House standards."
Those standards, developed in Germany in the 1980s, require buildings to be heavily insulated and practically airtight, minimizing heating and cooling loads. They also mandate high-efficiency ventilation systems to circulate fresh air. Thousands of buildings have been certified by the international Passive House Institute, or PHI, and its competitor, the Chicago-based Passive House Institute U.S. (PHIUS), and the numbers are increasing sharply. Plus, experts say, for every building certified there may be a dozen or more that follow some or all of the Passive...