In honor of the fifth annual US Passive House conference taking place in our fair city of Portland, Oregon this week, I want to introduce this exciting and relatively new standard for building efficiency known as Passive House.
I have been interested for many years in efficient building approaches. In the mid 80’s I had the opportunity to visit what Amory Lovins jokingly referred to as his “banana plantation in the Rocky Mountains”—his home and office of the Rocky Mountain Institute—and saw for myself the banana trees that grew well in the middle of the snowy Rocky mountain winters (they even had to keep windows open in the winter because it was too warm). I knew, and this proved to me, that there was a better way than the terribly inefficient standards of typical home and commercial construction being pursued here. Unfortunately, we haven’t advanced much in standards of efficient construction, but there are now some inspiring opportunities if given the proper focus and support.
In January 2009 I had the pleasure of hearing about a still relatively new approach to construction that was inspired by Amory Lovins and others experimenting in the US with super-insulated buildings that was later developed—in Germany with great attention to building science—into what has become the most rigorous standard in the world for energy efficiency, what’s called in German Passivhaus and translated into English, Passive House.
While the name in English is awkward and a bit confusing (people tend to confuse it with passive solar), Passive House could be the new gold standard in efficient building. The Passive House standard does not focus on a wide range of green building elements and therefore is not a replacement of LEED and the Living Building Challenge, it does however, zero in on the linchpin of green building: energy use. The Passive House standard also does not dictate a particular construction method, but sets an extremely high—but reachable—standard for energy efficiency which ensures that homes meeting this standard use 70 to 90% less energy than typical new homes built in the US (other building types find similar reductions in energy use).
In short, the Passive House standard requires the building to meet three stringent measures of performance:
• Maximum annual heating and cooling demand that does not exceed 15 kWh/m2/year (4.75 kBtu/sf/yr),
• Total energy consumption of not more than 120 kWh/sq m (38.1 kBtu/sf/yr) per year, and
• Airtight building shell of no more than 0.6 ACH @ 50 pascal pressure, measured by a blower-door test.
So what does this all mean? In short, it means that the focus is on an extremely efficient building envelope with ample insulation, strategically placed high-performance windows, very minimal thermal bridging (where heat and cold can easily transfer from inside to outside and vice versa), and efficient lighting and appliances. Further, this means that instead of a typical furnace, a single family home can be heated with a small auxiliary heater of 1000-2000 watts—when needed at all. In other words, we can trade our furnaces for something the size of a hairdryer. Also, since it creates an airtight envelope, a device (HRV-Heat Recovery Ventilator or ERV-Energy Recovery Ventilator) is used to constantly bring in fresh outside air which is warmed by the heat of the outgoing stale air from in the building, so it also enjoys an extremely high level of fresh, healthy indoor air quality.
Given the fact that US buildings currently consume ¾ of the electricity in the US—more than any other single sector—and is one of the key contributors to greenhouse gases, the opportunity to shift our new and existing building stock to this level of efficiency should be a top priority. Although the Passive House standard is just getting started in the US, it is growing quickly—following Europe’s lead, which has already built over 15 thousand buildings to this standard.
Look for more details on this in coming posts. Meanwhile, check out these links for more information:
Passive House Institute of the US
Passivhaus Institut (Germany) English site
Green Without Gizmos, Fine Homebuilding, April/May 2010
Can We Build A Brighter Shade of Green? New York Times story Sept. 2010
Snug and Tight House, New York Times graphic