A group of about 130 designers, builders, and Passivhaus fans gathered at U Mass Boston on October 27, 2012 to attend a one-day conference organized by Passive HouseA 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. New England.
It's impossible for this report to be comprehensive, unfortunately, and I won't be able to do justice to all of the conference events. My report will focus on three speakers: Adam Cohen, Chris Corson, and Roger Normand. Among the presentations not reported on here:
Adam Cohen is a designer at a firm called Structures Design/Build in Roanake, Virginia. In recent years, he has had a surprising degree of success convincing residential and commercial clients to build to the Passivhaus standard.
Cohen opened his presentation with some jokes about his corner of Virginia. “I work in the Bible Belt South,” said Cohen. “Right before I came up to this conference, my Obama yard signs were stolen. Someone suggested that I call this session, ‘Passivhaus in redneck country: Building for people who don’t care about the environment.’”
Cohen then shared an affectionate look back at his countercultural roots. “When I was 25, I was a hippie and an idealist,” he said. He showed us a photo of a house he built with his wife (see Image #2, below). “The house cost $3 a square foot. We lived on a commune. Back then, we were building off-grid houses. We were trying to live off the land. If we had 4 or 6 Arco solar panels, that was a screaming big PVPhotovoltaics. Generation of electricity directly from sunlight. A photovoltaic (PV) cell has no moving parts; electrons are energized by sunlight and result in current flow. system. We used gas appliances, wood appliances, gas refrigerators. We built thermosyphon solar hot water systems. We built hydraulic ram pumps out of PVC. Why did we go do all of this? Because we were poor hippies.”
Cohen has come a long way. He is now a successful designer of single-family homes and commercial buildings.
Here are more quotes from Cohen’s presentation:
On blower door testing: “We follow what I call the Duclos method of airtightness — named after Mike Duclos. First, we sheathe the entire building — right over the window and door openings, except for one door. Then we test it with a blower door, and fix any leaks we find. Then we install our windows and test again. Then we fix the window leaks. Finally, we do the mechanical rough-ins, and then test again and seal again.”
On commercial kitchens: “A commercial kitchen range hood in a Passivhaus? It can be done, but it’s not fun.”
Airtightness requires attention to details: “Liquid-applied air barriers are now standard for many commercial projects. We’re already doing a lot of this stuff, but we are doing it wrong. Why should we pay more just to do it right?”
How long is the payback period? “As soon as someone asks me about payback, I change the subject. I want to talk about return on investment.”
The advantages of design/build: “The traditional delivery system — with a separate architect, designer, owner, contractor, and subcontractors — is like an octopus with no brain. Design/build — integrated delivery — is a better system.”
Americans won’t accept hot interiors: “Europeans accept a wider indoor comfort range than Americans. But you can’t have overheating in America. We must meet the expectations of regular WalMart-going Americans — not just you and me.”
On PHPP: “There are tons of things in the PHPP that I don’t agree with. I know that a building doesn’t work with the PHPP defaults. Energy modeling is 25% science, 25% experience, 25% art, and 25% voodoo.”
Regular GBAGreenBuildingAdvisor.com readers are already familiar with Chris Corson’s work. Corson first gained national attention for designing and building an affordable Passivhaus in Knox, Maine. (For more information on that project, see Striving for Passivhaus Affordability and Cold-Climate Passivhaus Construction Costs.) Corson usually specifies triple-glazed Intus windows for his projects.
At the Boston conference, Corson shared photos and construction anecdotes from the Knox Passivhaus job as well as from a deep-energy retrofit project at his own house in Belfast. (GBA published a few photos Corson's deep-energy retrofit project in an article called A Real Chainsaw Retrofit.)
Here are some quotes from Corson’s presentation:
On sub-slab insulation: “The Knox Passivhaus has R-54 sub-slab foam. Under the slab is a great place to hide insulation. It’s one aspect of a house that can’t be retrofitted.”
On space heating systems: “The house is heated with a single ductless minisplit, a Mitsubishi MUZ-FE12NA [outdoor unit] and a MSZ-FE12NA [indoor unit].”
On airtightness: “We blower-door tested the house 7 or 8 times. It ended up at 0.284 ach50.”
On the deep-energy retrofit project at his own house: “Before the retrofit, the house burned 1,100 or 1,200 gallons of oil per year for space heat and domestic hot water. We did a chainsaw retrofit, the method developed by Harold Orr and Rob Dumont. We cut the eaves off the house. We took a straight-up PERSIST approach, and wrapped the entire house with Ice & Water Shield. It was expensive. Then we installed 5.5 inches of polyisoPolyisocyanurate foam is usually sold with aluminum foil facings. With an R-value of 6 to 6.5 per inch, it is the best insulator and most expensive of the three types of rigid foam. Foil-faced polyisocyanurate is almost impermeable to water vapor; a 1-in.-thick foil-faced board has a permeance of 0.05 perm. While polyisocyanurate was formerly manufactured using HCFCs as blowing agents, U.S. manufacturers have now switched to pentane. Pentane does not damage the earth’s ozone layer, although it may contribute to smog. to wrap the house. We bought the used polyiso from Insulation Depot. We used a lot of 8-inch Timberlock screws — 4,000 or 5,000 Timberlocks.”
On Lunos fans: “We installed eight Lunos ventilation fans — four pairs of fans. It’s a really cool device. It has a ceramic core for heat recovery. The fans cost $1,200 a pair, and they are quiet. We’ve lived in the house for nine months. The air quality is definitely better. The fans are performing better than expected.” (For more information on the Lunos ventilation fan, see European Products for Building Tight Homes.)
On fiberboard sheathingMaterial, usually plywood or oriented strand board (OSB), but sometimes wooden boards, installed on the exterior of wall studs, rafters, or roof trusses; siding or roofing installed on the sheathing—sometimes over strapping to create a rainscreen. : “On some projects we’ve used high-perm fiberboard for exterior sheathing. It’s made in Canada, and it’s expensive. It worked; it did its job. But it’s difficult to work with. It’s hard to install. It’s dirty. It smells like asphalt. When we started installing the cellulose insulationThermal insulation made from recycled newspaper or other wastepaper; often treated with borates for fire and insect protection., it really bellied out. Fortunately we caught the bellying before it became a big problem. We finished the job by watching it closely and babysitting the insulation contractor.”
On the new European membranes: “We’ve done homes without exterior sheathing using an exterior membrane system called Solitex Mento Plus. This stuff is waterproof and UV-resistant. It’s simple and fast to install, and clean to work with. It does require a considerable amount of strapping. You need battens and counter-battens to keep it from bowing out. Even with all those battens, there still is some bowing. We have also used membranes on a roof. We installed Solitex Mento 1000 as a sarking membrane over the roof trusses. It’s waterproof. Again, there is no exterior sheathing — just standing-seam metal roofing over the purlins. We did install OSB under the roof trusses as an air barrier, however.”
Roger Normand (like Chris Corson) is well known to regular GBA visitors. Roger and his wife Lynn are building a new custom home in Saco, Maine, and they are aiming to meet the Passivhaus standard. For the past several months, GBA has been publishing Roger’s blogs about his new home, which is still under construction.
Guided by architect Chris Briley and energy consultant Marc Rosenbaum, the Normands have been discovering the joys and complications inherent in most Passivhaus projects. Roger's blogs describe the downs as well as the ups of building a new custom home.
At the October 27 conference in Boston, Roger Normand and Chris Briley took turns presenting information on the Normands' new home. I've excerpted a few quotes from Roger Normand's presentation below.
On fossil fuel: “I worked for the Department of Defense. Our energy policy is based on using the military to protect our energy supplies.”
On the Passivhaus standard: “I read a lot of things about designing high-performance homes. I stumbled onto LEEDLeadership in Energy and Environmental Design. LEED for Homes is the residential green building program from the United States Green Building Council (USGBC). While this program is primarily designed for and applicable to new home projects, major gut rehabs can qualify. , and then I stumbled onto Passivhaus. I liked the intellectual rigor of the standard. I liked the fact that it was a performance metric. But I’ve discovered that we must pay a huge premium for high-performance windows and high-performance ventilation equipment. And you can’t count the output of your PV system toward meeting your Passivhaus goal, which doesn’t make sense to us.”
On appraisals: “If you’re building a house, you have to go to the bank. The bank wants an appraisal. We’ve learned that it ain’t easy. We’ve contacted three appraisers. They all professed to have green credentials. The first appraiser gave a value of zero for the energy efficiency features of our home. I went ballistic. Fortunately, the bank agreed with me. Finally, a different appraiser gave us credit based on the value of being net-zero for seven years. Why seven years? Well, that’s how long Americans usually stay in a house before they move. This is really a ‘no tickee, no laundry’ situation. People can’t afford energy features because the appraiser won’t put any value on it.” (For further discussion of this topic, see Roger Normand's latest blog, Seeing Red on a Green Property Appraisal.)
On specifying windows: “Picking windows is not easy. We are stuck with going with European windows. We started with Pella windows, but their performance was not even close to what we needed. Picking windows is not intuitively obvious.”
On the bottom line: “It ain’t cheap going green. We’re going to end up at about $220 per square foot.”
The last event of the day was a panel discussion moderated by Jesse Thompson, who introduced the featured speakers — Adam Cohen, Marc Rosenbaum, and me — as “three old hippies.”
Since I was sitting at a table in front of the crowd, I was unable to take notes, so I can't report on what was said. Fortunately, there is a video of the panel discussion. Here is the first segment of the video:
Below are links to Part 2 and Part 3 of the panel discussion:
Martin Holladay’s previous blog: “Fans in the Attic: Do They Help or Do They Hurt?”