Passive House Gets Active
March 03, 2011
A version of this article appears in the March/April 2011 issue of Home Energy Magazine.
Portland, Oregon, is a hotbed of sustainable building. In keeping with that tradition, the 2010 North American Passive House Conference was held there November 4–7, 2010. Almost 350 architects, engineers, builders, and energy consultants from 41 states and six Canadian provinces came to listen to Passive House experts from around the world. Topics included the building science behind the Passive House standard, applying Passive House principles to various building types (new construction and retrofits, residential and commercial), the certification process, and lots of case studies. It was a chance for Passive House supporters to mix and mingle and show off their latest projects, and for those new to the Passive House standard to learn more about this up-and-coming building technique. This was the second annual North American Passive House Conference, with attendance about 30% greater than the first.
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Passive House Primer
The Passive House standard evolved from the superinsulated houses of the 1970s and the research surrounding them. German physicist Wolfgang Feist and Swedish professor Bo Adamson developed it in response to a rigorous energy standard introduced in Sweden in 1988. From 1988 to 1996, Feist refined the underlying concepts and the modeling software. He founded the original Passive House Institute in 1996 in Darmstadt, Germany. (For more on Fiest, see “Interview with Passive House Pioneer,” p. 20.)
A Passive House is designed to be extremely energy efficient. In order to be certified as a Passive House, a building has to meet only three criteria:
- Space heating and cooling cannot exceed 15 kWh per square meter per year (4.8 kBtu/ft2 per year).
- Source energy cannot exceed 120 kWh per square meter per year (38.1 kBtu/ft2 /year).
- Building air tightness cannot exceed 0.6 ACH50.
If you can achieve these goals, you have reduced the energy consumption of the building by roughly 90% over a typical code-built building. Once you reduce your utilities that much, it’s easy to get to net zero energy. Results like these are also promoted by ACI’s Thousand Home Challenge for retrofits (see “The Thousand Home Challenge,” HE May/June ’09, p. 22), and EPA’s next-generation Energy Star program for new construction (see “Energy Star for Homes 3.0,” HE Jan/Feb ’11, p. 6).
What separates the Passive House certification process from most other third-party building certifications is that these benchmarks must be met by blower door testing and analysis of a year’s utility consumption data. You don’t get the certificate unless you can prove that you meet the requirements.
It’s hard to hit these goals via trial and error. Most modeling software isn’t very helpful, either—most energy consultants agree that modeling software isn’t usually very reliable for predicting a building’s energy use. The Passive House standard uses a complex spreadsheet, called the Passive House Planning Package (PHPP), developed by Feist, to predict energy use. Passive House experts contend that it does an excellent job of predicting energy use because it is calibrated to measured performance data. Apparently it’s not that easy to use—a large part of the Passive House Consultant certification training involves learning how to use the PHPP.
The secret behind building a successful Passive House is really no secret at all. The building science has been know for decades:
- Eliminate thermal bridges.
- Make the building airtight.
- Install an energy or heat recovery ventilator (ERV/HRV).
- Use high-performance windows.
- Optimize passive solar and internal heat gains.
For Passive House certification, you design your building using the PHPP software, incorporating those principles; test the airtightness; and then prove you meet the utility consumption thresholds after a year. On the surface, the certification process seems much simpler to manage than some of the prescriptive-based programs like LEED. The only real stumbling blocks are the PHPP modeling, which is not trivial, and actually building the building to the model specifications.
A common complaint about most green-building programs is the additional cost required to meet a certification or a strict set of building specifications. Program supporters have a tendency to search for convincing cases that prove that it really doesn’t cost any more to build a sustainable house, so as not to scare away potential builders or homeowners. Passive House advocates, on the other hand, are very realistic about costs. The figures usually tossed around indicate that it costs from 7% to 15% more to build a Passive House. As with all green-building programs, once you factor in reduced utility, health care, and productivity costs, those margins go down, perhaps even to zero. (For more on Passive House, including book reviews, see “Resources.”)
The 2010 Passive House Conference started with a full day of advanced Passive House Consultant workshops. These were open only to certified Passive House Consultants or people who had already taken most of the consultant training. The two-day public conference, with Katrin Klingenberg acting as hostess, kicked off the following day with a short opening speech by Sam Adams, Portland’s mayor. He focused on the city’s longtime support for all things sustainable and green, and the community’s support for related public programs. Closing, he suggested that all conference attendees go to one of the local microbreweries or wine bars and request a free beverage in return for our support of Portland’s ambitions.
The mayor was followed by several keynote speakers who all had interesting things to say about climate change, the Passive House standard, and related topics. There are about 20,000 certified Passive Houses in Europe, the bulk of them multifamily buildings. There are currently only a handful in North America. All the speakers agreed that the Passive House standard, or a similar approach, is the only way we will avert significant climate change within the next few decades. As one speaker put it, if we can limit climate change to 2ºF, we might survive as a species. Most speakers also agreed that the principles behind the Passive House standard and net zero energy homes have to be incorporated into building codes in order to be successful. Examples include California’s current legislative initiatives and Denmark, which is legislatively targeting Passive House-level performance starting this year.
The rest of the conference included three or four simultaneous breakout sessions on a variety of topics. There were lots of case studies, mostly of buildings that are not yet certified (they have to wait until some actual performance data are collected before receiving certification). A session on the certification process made it clear that it’s not really as simple as it might at first seem to get a building certified. There are documentation and paperwork requirements, and you have to submit a certification package to a certifying agency. One of the most interesting sessions was on mechanical systems for Passive Houses. Compared to a typical forced-air or radiant system, a Passive House can usually be heated and cooled with a minimum of low-cost equipment. The insulation and building envelope do the real work. One other interesting session focused on Passive Houses in a hot-humid climate. The original standard was developed for European climates, which are predominantly heating climates. There are special challenges when you try to build a Passive House in a climate like that of New Orleans.
There were ample networking and exhibit times on the agenda. Not surprisingly, there were a lot of window vendors exhibiting. There were also several ERV/HRV vendors. The closing session on November 6 featured Dr. Wolfgang Feist and Rocky Mountain Institute founder Amory Lovins (via video). Lovins built possibly the first building in the United States patterned after the Passive House standard, after visiting Dr. Feist in Germany. The final, optional, day include a tour of Passive Houses in the Portland area. More than 130 people went on that tour, a healthy turnout.
Not So Passive Anymore
Overall, this conference was very interesting. There were more case studies than I would have liked and less building science than I would have liked, but it was definitely educational. Many of the presenters were from Europe, where they have a lot more experience with Passive House construction than we do in the United States. It was interesting to hear the European point of view. On top of that, the food was good, the weather was great, the facility was very nice and reasonably priced, and the crowd was interesting.
The Passive House approach is just one of many competing standards for alleviating climate change, reducing our dependence on petroleum products, and building better houses. There are many voluntary regional and national green-building standards and certification programs, and we’re starting to see more and more mandatory green building codes. It’s becoming difficult to keep track of all these things. I’m hoping that at some point in the future, we see a convergence of some of these standards. As one of the European conference presenters suggested, the only way to really solve the problems related to climate change is through national building codes and standards. If that ever happens in the United States, which is questionable, I hope that parts of the Passive House standard are included in that code.
Steve Mann is a HERS rater, Green Point rater, LEED AP, Certified Energy Analyst, serial remodeler, and longtime software engineer.
The Passive House Institute is the original Passive House online resource that promotes the work of the Passive House creator Wolfgang Feist. Although this is a reasonable English-, French-, and German-language resource, Passipedia provides much more content in a readily digestible form.
Passipedia is the definitive online resource on the Passive House standard. The wide-ranging content, in both German and English, includes articles about Passive House basics, construction detailing, building certification, case studies, and much more. Members of the International Passive House Association (iPHA) have special access to content that is more in-depth.
With more than 20 national Passive House advocacy and certification organizations around the world, the movers and shakers in the Passive House community decided to create an international umbrella organization. iPHA’s focus is to promote the Passive House standard and increase public and media awareness.
PHIUS is the North American iPHA affiliate responsible for certifying Passive Houses and Passive House consultants in the United States. PHIUS produced the 2010 North American Passive House Conference. It also provides ongoing Passive House consultant training.
Homes for a Changing Climate (2008)
This 100-page, small-format (6 inch x 8 inch) book is coauthored by Katrin Klingenberg and Mike Kernagis, PHIUS cofounders, and Mary James, former Home Energy publisher. It contains a brief introduction to the Passive House standard, followed by nine case studies. Most of the case studies are not actually Passive House-certified projects, but they do demonstrate applying Passive House principles to new and retrofit construction. Readers looking for construction detailing or hard-core building science should consult some of the on-line resources. Available at homeenergy.org and lowcarbonproductions.com.
“Passive Efficiency” and “Passive House” (Home Power, Issue 138).
This pair of articles by Katrin Klingenberg and Mike Kernagis, Passive House Institute US co-founders, is a good introduction to the science and art of Passive Houses.
Recreating the American Home: The Passive House Approach (2010).
This book, the second Passive House book by Low Carbon Productions, contains a brief Passive House introduction and 10 case studies. At 100 8.5 inch x 9 inch pages, including lots of photos, it doesn’t contain a huge amount of detail, but it’s the most in-depth Passive House book currently on the market. Each case study includes an extensive description of the project, basic floor plans, often some construction detail drawings, and quite a few color photos. Projects include new homes, various types of retrofits, and even a factory-built modular home, in a variety of North American climates. The text mixes very basic building science with some very detailed construction assembly descriptions, an interesting juxtaposition.
There’s a certain amount of repetition from case to case, but there is also a lot of good information as well. The extensive color photos give the book the feel of a small-format coffee table book—attractive, but not necessarily an in-depth resource. Personally, I could use more construction drawings and photos, and fewer interior and exterior design shots. Window and ERV/HRV manufacturers, and envelope sealing and insulation products are usually mentioned by name, but it’s time consuming to refer back and dig them out. An annotated product glossary would make that much easier.
Those minor criticisms aside, Recreating the American Home: The Passive House Approach is a good introductory book if you want to know more about the Passive House standard and how real people are using it on real projects. It’s inspiring to see the energy efficiency that you can achieve with a tight envelope, high insulation levels, and extreme attention to detail.
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