Image Credit: Image #1: Scott Gibson Chris Corson (a Passivhaus builder from Maine) and Bill Hulstrunk (National Fiber's cellulose expert) on the trade show floor.
Image Credit: Images #2 through #6: Martin Holladay Tomas O'Leary (co-founder and managing director of the Passive House Academy in Ireland) enjoying stuffed grape leaves and pasta-on-a-toothpick at an evening party at Performance Building Supply in Portland. Bob Irving (a certified passive house consultant from New Hampshire) and Chris Briley (one of the Maine architects who hosts the Green Architects' Lounge at GBA). Jesper Kruse (a Passivhaus builder from Maine) and Marc Rosenbaum (director of engineering at South Mountain Company in Massachusetts). If you like the looks of this cork-filled, aluminum-clad European entry door, you can order one from Yaro Windows and Doors (Cambridge, Massachusetts) for about $3,000 to $4,000, plus shipping.
The North American Passive House Network held a two-day conference in Portland, Maine, this month. The well-attended conference drew attendees from all over the U.S., as well as from China, the U.K., and Germany.
Because it was a four-track conference, it was impossible to attend every session — a frustrating fact for attendees. Many of the experts who gave presentations at the Portland conference have written for, or been featured in, Green Building Advisor; among the familiar names were Matthew O’Malia, Chris Corson, Dylan Lamar, Malcolm Isaacs, Nabih Tahan, Peter Schneider, Graham Irwin, Marc Rosenbaum, Tim Eian, Jesper Kruse, and Phil Kaplan.
With so many smart people gathered together under one roof, the conversations in the hallways and at the lunch tables were almost as valuable as the presentations. Like most people who attended the conference, I learned a lot while I was there.
It was exciting to see so many consultants, designers, and builders present their latest projects. These construction professionals are doing excellent work. At the Portland conference, they talked about their mistakes, presented information on new methods, and shared data. In many cases, Passivhaus builders are discovering new, less expensive ways to build excellent buildings — including some of the best homes being built in North America today.
Dr. Feist flew in from Europe
Dr. Wolfgang Feist, the founder of the Passivhaus Institut in Darmstadt, Germany, gave the conference’s keynote address on Monday morning, September 22.
According to my notes, Feist made five important points:
- The Passivhaus standard is based on science.
- Building to the Passivhaus standard is cost-effective.
- There is no need for climate-specific standards.
- The Passivhaus Institut has developed a primary energy factor for renewable energy.
- The Passivhaus Institut has announced three new construction standards.
The Passivhaus standard is based on science
At the beginning of his address, Feist repeated one of his points at least three times. Referring to the Passivhaus standard, he told the audience in Portland, “The background of this is science. … It’s about science. … It’s a concept which is based on science.”
He named five scientists whose work helped smooth the way for the Passivhaus standard: Arne Elmroth, Bernd SteinmÃ¼ller, Vagn Korsgaard, Claes Bankvall, and William Shurcliff. Since the first Passivhaus was built 23 years ago in Darmstadt, Germany, it is now possible to say that the Passivhaus concept is “long-term tried and tested.”
Meeting the Passivhaus standard is cost-effective
Feist acknowledges that Passivhaus buildings cost more to build than conventional buildings. “There is some extra investment,” said Feist, but these expenses “are a good idea.”
Feist said, “Good windows are an important part of the development of Passivhaus.” As better building materials become available, Feist predicted, “we can reduce the overall investment costs.” He also noted, “We are not in love with insulation. We just use as much as we need to make it a Passivhaus.”
Feist conceded, “Heat-recovery ventilation at the moment is a little bit more expensive in a Passivhaus. We are open to saying that. We are going to change that. We have ideas to improve these heat-recovery systems and reduce the cost of these systems, and to have a collaboration of scientists and industry. But already now, heat-recovery systems are improving internal comfort and are worth the investment.”
When calculating the value of any investment in energy features, Feist advised, “Forget about payback time. Payback is misleading. It is not a good measure for the economic result of an investment.” Instead, Feist advised the audience to focus on net present value. (For more information on net present value calculations, see Payback Calculations for Energy-Efficiency Improvements.)
Feist stressed that the Passivhaus standard is cost-effective. He said, “Least cost is the standard of the Passivhaus.”
There is no need for climate-specific standards
Feist’s discussion of climate-specific standards was an apparent response to the recent efforts by the Passive House Institute U.S. (PHIUS) to develop climate-specific standards for North America.
Feist said, “We have a lot of climates in the U.S., but there is an even broader spectrum of climates in China. We can build to the same standard everywhere. There is no different physics in China. The solutions of the equations might be different, but the physics is the same.”
Responding to architects who question whether the Passivhaus standard is appropriate for hot, humid climates, Feist discussed design strategies that work in New Orleans. “The dehumidification load is a big load in New Orleans,” said Feist. “You reduce the dehumidification load with better airtightness. The other thing is humidity recovery, using what is called here ‘energy-recovery ventilation.’ … Outside air tends to be humid, but this device [an ERV] can take away a big part of the humidity.”
Feist admitted that Passivhaus buildings need an HVAC system. “It is not about avoiding any kind of HVAC system,” Feist said. “In a humid climate, that’s not possible. There are sources of humidity inside the building. There is always a minimum of latent load. So, yes, there is an active part in a Passivhaus in New Orleans, just as there is a small active heating system in a Passivhaus. The important thing is that the loads are low.”
A primary energy factor for renewable energy
Feist spent several minutes discussing efforts by the Passivhaus Institut to develop a primary energy factor for renewable energy systems (chiefly PV). Here’s the logic behind this new factor: those who design net-zero energy homes shouldn’t assume that a kilowatt-hour of electricity generated by a PV array in June is equal to a kilowatt-hour of electricity used for space heating in December. Feist contends that these two kilowatt-hours are not equivalent.
He put it this way: “The net zero energy approach is misleading. You can’t substitute missing electricity during the winter with excess electricity produced during the summer.” Feist calculates that a house can’t truly be considered net-zero unless it has a PV array that generates about twice as much electricity on an annual basis as its occupants use.
With a PV array, Feist said, there is “a lot of energy during the summer, less in winter. … The winter gap is a problem — the electricity used for heating.”
Feist continued, “There is still need for energy storage.” According to Feist, “short-time storage is no problem,” but “seasonal storage is not as easy as a lot of people thought. Maybe you need a flywheel or battery. If you load a battery once a year, how expensive will it be? No chance this will work. It would be extraordinarily expensive. … There is no problem on a daily basis. But this won’t work on a seasonal basis.”
Another possibility is thermal storage. “Thermal storage is not inexpensive. It requires huge storage devices. It might be possible, but in narrowly crowded areas in Europe it is not possible. And it will still be too expensive for seasonal storage.”
What’s the solution to long-term storage? According to Feist, “You have to change the energy into chemical storage” — hydrogen or methane. Feist said, “We calculate how much [PV] energy you can use directly, and how much goes into short-time storage, how much into seasonal storage.”
Feist foresees a future that includes long-term storage of renewable energy. He said, “At some moment you have to store it, and some [of the energy] will have to be stored on a seasonal level, at an efficiency of 25% to 35% percent. That’s not a bad thing. It’s not a big problem, but we have to be aware of it. We need more primary electricity to get the net energy we need.”
Feist said, “When we look into primary energy factors for renewable energy, [the factors] will depend on whether it is used for heating or for a washing machine.”
The Passivhaus Institut has come up with a primary energy factor for renewable energy — an annualized average for all different categories of domestic electricity use — that varies according to one’s geographical location. It doesn’t vary by much; the range is from 1.8 to 2.0.
Three new construction standards
Feist ended his address by outlining the three new construction standards that were announced by the Passivhaus Institut in April 2014.
As Ken Levenson reported in his May 2014 article about the Passivhaus conference in Germany, the three new construction standards are known as Passive House Plus, Passive House Premium, and Energy Conservation Building.
The Passive House Plus standard will require adherence to the Passivhaus standard, as well as the inclusion of an onsite PV array sized to make the building net-zero.
The Passive House Premium standard will include a bar that is even higher than Passive House Plus, requiring a building to have a larger PV array so that it is energy-positive.
The third standard, called the “Energy Conservation Building Standard,” will be less stringent than the current Passivhaus standard. Energy Conservation Buildings will be allowed to use about twice as much energy as would be consumed by a comparably sized Passivhaus building.
There are critics
Readers of GBA probably know that I have written that the Passivhaus standard is arbitrary and compels cold-climate designers to include very thick insulation that isn’t cost-effective.
Since my July 2005 article in Energy Design Update (highlighting energy use data from the multifamily Passivhaus project in LindÃ¥s, Sweden, that revealed that each of these “apartments without heating systems” actually required 1,800 kWh per year of electric resistance space heating), I have written several articles on this topic. Among these articles are my August 2009 article, Can Foam Insulation Be Too Thick? (written with input from John Straube) and my April 2011 article, Are Passivhaus Requirements Logical or Arbitrary?
While Katrin Klingenberg, the founder of PHIUS, was at first rather dismissive of these criticisms, her opinions have gradually changed.
In a blog which she posted on February 27, 2014, Klingenberg was remarkably gracious. She wrote, “Looking back, I see there was another critical group — and I mean critical. Let’s call them the passive house skeptics. They’ve ranged from Marc Rosenbaum to Joe Lstiburek to Martin Holladay. … I didn’t understand it at the time — and misunderstood it as resistance to change. It was quite the opposite. It was the notion that this passivhaus or passive house was new that was irksome to them. … What we have learned — and I say we because we’ve learned it side-by-side with CPHCs and builders who’ve faced real-world challenges across climates — is that this group of early pioneers had valid misgivings about passive house as formulated in Europe. The concerns included the small-house penalty, North American issues with latent humidity, and the cost-effectiveness of investing in the envelope as opposed to renewables. The biggest concern: deep disagreement that a single numerical standard for all climate zones could make sense.”
Feist’s remarks invite analysis
While Feist never mentioned the traumatic PHI-PHIUS divorce, it’s clear that he has been closely following developments in North America. Why else would he have devoted as much time as he did to the topics of climate-specific standards and the challenges presented by the climate of New Orleans?
While many U.S. designers and builders feel a sense of loyalty to the Passivhaus Institut in Darmstadt, others have clearly chosen to align themselves with PHIUS. The fact that there were two important Passive House conferences in the U.S. in a single month — the PHIUS conference in California and the conference in Maine that featured Dr. Feist — is evidence that the PHI-PHIUS split remains unhealed.
A full response to Feist’s keynote address is beyond the scope of this report. But here are some reactions that popped into my head as I listened to Feist in Portland:
- Passivhaus is “a concept which is based on science.” While today’s building scientists certainly owe a debt to the scientists who performed ground-breaking research on building performance and airtightness, our debt of gratitude is irrelevant to the question of whether the energy-use limits established by the Passivhaus Institut are arbitrary or not.
- On cost-effectiveness. Although the levels of insulation required to meet the Passivhaus standard in Darmstadt may, in fact, be cost-effective, that doesn’t mean that the levels of insulation required to meet the Passivhaus standard in Minnesota are cost-effective. It takes much more insulation to hit the same energy target in Minnesota than it does in Darmstadt.
- “Physics is the same.” Feist dismissed calls for climate-specific standards by saying, “The solutions of the equations might be different, but the physics is the same.” Of course the physics is the same. But when the “solutions of the equations” call for R-80 insulation instead of R-40 insulation, the cost-effectiveness of the last R-40 needs to be calculated. Maintaining that an energy use target of 15 kwh/m2*year is the magic sweet spot for every single location on the planet defies logic.
- A primary energy factor for renewable energy. It’s hard to tell whether the logic that Feist used to develop a primary energy factor for renewable energy indicates that he thinks that seasonal storage of renewable energy is likely to be implemented soon, or whether the exercise is simply an academic method for obtaining a factor that will be useful for his new construction standards. If it’s the former, I think that his prediction is unlikely to come true. I doubt if we’ll be using PV arrays to produce hydrogen during the summer in the foreseeable future.
Fortunately, I had the chance to follow up on some of these issues when I sat down with Dr. Feist after his speech for an interview. I’ll publish that interview next week.
Martin Holladay’s previous blog: “Brick Buildings Need Roof Overhangs.”