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passive house

A Passive (aggressive!) approach to energy use

In November 2010, Build Boston featured a comprehensive exploration of the Passive House standard by those who have helped it succeed in Europe and those on the forefront of its emergence in North America.

To whet the industry’s appetite for learning more about this cutting-edge approach to design and construction, the BSA recently sat down with Dr. Harald Rohracher, who was visiting from Austria’s Alpen-Adria-University, and Paul Eldrenkamp, of Byggmeister and the DEAP Energy Group, to discuss Austria’s great success in adopting the Passive House standard and how Massachusetts can emulate it.

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What is Passive House?

Eldrenkamp: Passive House is a very simple, clear building standard, which has just three criteria: the amount of total energy a house or a building uses; the amount of total energy that can go to heating and cooling; and an air-tightness standard that’s tested with a blower door. It doesn’t include any criteria for what’s traditionally been viewed as green building in the United States—for example, there’s no water-usage or material-sourcing category.

How does Passive House compare with LEED?

Eldrenkamp: The biggest difference is that LEED covers eight different categories, whereas Passive House covers just one directly. (Indirectly, it covers a range.) If you compare Passive House to the energy-usage component of LEED, you’ll find that LEED doesn’t really set a specific target: It gives a maximum that is really a pretty modest baseline. One of the backlashes against LEED has been that LEED buildings really have not demonstrated significantly less energy usage than buildings built to code. For example, with LEED residential construction, you only need to hit the Energy Star standard, which is only 15 percent better than code.

With Passive House, it’s all about the energy use. It dictates a very specific energy budget that you cannot exceed. By mainly focusing on energy efficiency, at the residential level, Passive Houses use only about one-fifth of the energy that a building constructed to code would use—for an 80 percent reduction in energy consumption.

How does Passive Haus achieve that level of efficiency?

Eldrenkamp: Passive House calls for super-insulation (which means triple-pane windows and thick walls), a ventilation system with very efficient heat recovery and, at least in heating climates, passive solar gains.

Rohracher: Thanks to this efficiency, the energy needs of Passive Houses are so low that internal heat production by their inhabitants—including people, computers and other systems—can meet a significant part of their energy-supply needs.

Is there a way to predict internal gains?

Eldrenkamp: The Passive House Planning Package (PHPP) is an Excel spreadsheet that has about 35 different tabs. It’s a very precise German tool with detailed data input to calculate the internal gains.

How successful have Passive Houses been in Europe?

Rohracher: The first Passive Houses were built in Germany in the early 1990s by Wolfgang Feist from Germany in cooperation with Bo Adamson from Sweden. They developed both the concept for the Passive Houses standard and the framework for its dissemination: the Passivhaus Institut in Darmstadt, Germany. The institute has developed an international network of professionals and coordinates the software package supporting the energy-efficient design of Passive Houses (the PHPP) and certifications for the different components, among other activities.

The Passive House concept spread to Austria a few years later, and now Austria has five times as many Passive Houses per capita than Germany. By the end of 2009, there were already close to 7,000 Passive Houses in Austria, and we are estimating that, by the end of this year, 25 percent of all new building construction in Austria will be to the Passive House standard. Around Europe, 22,500 Passive Houses have been built so far.

So the standard really has taken off, and it’s becoming more and more popular. Regulations are starting to adapt, and there are subsidies encouraging its more widespread adoption.

What is the state of Passive Houses in the United States?

Eldrenkamp: In 2002, the first Passive House was built in the United States by a German architect named Katrin Klingenberg. She had just moved here and was pretty discouraged with the energy-efficiency standards of the American housing market. She built a Passive House in Urbana, Illinois, and then another, before founding the Passive House Institute U.S. in 2005. The institute held its first round of Passive House consultant training in 2008, with about 20 people passing the exam and becoming certified Passive House consultants.

We’re not two years away from the completion of that first training session, and the Passive House standard has really taken on a life here. Many architects, builders and engineers are growing disillusioned by the green building movement and its overall lack of rigor, accountability and impact. It seems to a lot of us that the movement has been more about putting a greenish tint on business as usual than really moving the design and building industry toward making significant reductions in greenhouse-gas emissions. Passive House is an attractive standard because it’s rigorous and quantifiable.

Currently, there are maybe only 10 certified Passive House buildings in the U.S., but there are many more under construction, in design and in the pipeline.

Have any local projects met Passive House standards?

Eldrenkamp: There’s one on Martha’s Vineyard that I believe may have hit the final standard. I know it was getting very close. The project hadn’t achieved the air-tightness standard last I heard, and I don’t know if they’ve been able to make the necessary tweaks yet. But that’s been up and running for more than a year now.

There’s a project nearing completion in Shrewsbury. I’m involved in planning a Passive House project in Falmouth that should break ground in about six weeks. There is also an architecture firm in Maine that’s developing stock Passive House designs that could be adapted to local climates.

How does Austria’s climate compare with New England’s?

Rohracher: I believe it’s rather similar, though Austria’s mountains are sometimes a bit colder.

Eldrenkamp: I would agree. The Department of Energy has defined seven climate zones in the U.S. New England is climate zones 5 and 6, with our most- northern states being zone 6 and the rest zone 5. Austria is right around climate zones 4, 5 and 6, depending on the elevation.

However, Austria doesn’t have the same de-humidification and cooling needs as New England. We’re still trying to address those issues here and still fall within the Passive House energy-usage parameters.

What led to the speedy adoption of Passive Houses seen in Austria?

Rohracher: There were many different aspects, all of which were important. Austria focused strongly on architectural quality; in Germany, the movement was perhaps more engineering-driven. Passive Houses started off in a region in Austria where there was a strong emphasis on high-quality buildings, both in terms of energy efficiency and great design.

That region managed to set up a network for both architects interested in Passive Houses and the businesses that supplied and adapted components for them, such as window manufacturers and producers of ventilation systems. The area also was home to a strong intermediary organization, the Energy Institute, so there was a coordinated effort in setting up a structure for Passive Houses.

Nationwide programs, such as the Building Of Tomorrow program, focused on the research and development side—creating better building components, but also providing sociological research on perception and use.

There was also a strong focus on vocational training for diverse building-industry professionals and an emphasis on public awareness programs, including media campaigns and excursions to Passive Houses—with the ability to rent Passive Houses for a few days or weeks to “test them out.”

Can you only meet Passive House standards through new construction?

Rohracher: The original concept was focused on new construction, but there is huge potential to use Passive House knowledge and technology for retrofits. The latest available figures for Austria showed only 50 retrofits in 2008 meeting the Passive House standard, but that number is growing quickly. It’s certainly more difficult to meet Passive House standards via retrofitting, because you can’t change buildings’ orientation and factors like that. But you can apply different Passive House components, such as super-insulation and highly insulated windows, and get very close to the standard, if not all the way there.

Can you really apply Passive House standard to commercial buildings?

Eldrenkamp: “Passive House” is a direct translation from the German, where “haus” means “building.” So the concept can apply to diverse building types, from single-family homes to large office buildings.

Rohracher: Yes. The concept was originally used in Germany for modest residential buildings. But more recently in Europe, we have seen the Passive House standard applied in non-residential buildings, including schools, factories, supermarkets and office buildings.

How much does it cost to build to the Passive House standard?

Eldrenkamp: In the U.S., it may cost only 5 to 10 percent more to design and build a new home to the Passive House standard. But we have found that while it’s not impossible to retrofit an existing home to the Passive House standard, it’s prohibitively expensive in most cases: sometimes equaling 80 percent of the cost of new construction. So that’s problematic.

Rohracher: It depends on what the building looks like and how easy it is to retrofit. I’ve just seen recent figures from Austria, where retrofitting to the Passive House standard cost on average only 10 to 15 percent more than standard renovations. Our experience in Austria is that, with new buildings, Passive House construction only costs 3 to 5 percent more than regular construction. The economics are getting better all the time, as we become more experienced and Passive House materials become cheaper and more widely available.

What is the return on investment for Passive House construction?

Rohracher: In Europe, if you sell a building, you have to provide some certification of how much energy it uses. So an investment in Passive House construction increases the value of the property. If there is this kind of incentive around new construction, you don’t need to have long-term plans for a property to realize a return on your investment.

Eldrenkamp: In the U.S., however, people often have a very short-term view on construction costs. On average, people move about every seven years and tenant leases are typically only a few years long, too.

In addition, I don’t really like the idea of using simple payback formula for energy-efficiency improvements to homes and offices because the service life of a building is so long. In Boston, for example, we have buildings with a service life measured in centuries, whereas our ability to predict energy prices is measured in days.

That said, it is so much cheaper to build for maximum energy efficiency at a building’s outset, that it seems nuts to make value-engineering decisions that will last 100 years. One of things I found most compelling about the Passive House standard is that it says this is a useful energy budget, not only in terms of building economics but also in terms of sustainable use of the world’s energy resources.

And when you’re designing to a specific budget, the question becomes how do we most cost-effectively build this structure to get to this specific goal? That is a very different conversation from what’s cost-effective in terms of our ability to anticipate where energy costs are going to go over the next few years or even decades.

What are the barriers to moving toward adopting Passive House standards?

Eldrenkamp: One barrier is the general availability of components—primarily that really good windows are still inordinately expensive. We have not traditionally asked much of windows in the U.S., and the difference between the window you can use in a Passive House and the window that meets code is huge. You’re doubling or tripling the cost of your windows right there.

The HVAC and mechanical systems here are also lacking. In Europe, they have these elegant all-in-one units that do heating, cooling, ventilation and domestic hot water—all in a component that fits into a small linen closet.

Europe also has a wider range of insulation, more widely available. We can find all the same insulation here, but some of it is just very difficult to get in quantity or cost effectively.

So there’s the availability of building components part, which is solvable long-term, but there’s also consumer resistance to certain components. In a Passive House, you probably want to go with casement windows rather than double-hung windows. You likely want to have an electric range top rather than a gas cook top. You definitely don’t want an open fireplace. And ideally your dryer is a condensing dryer, so it’s not vented to the outside.

From the industry’s perspective, the biggest barrier is the initial cost: the investment in basically learning a new language. Austria is “exhibit A” that building to the Passive House level of performance gets easier with time. But it definitely costs a lot more to do your first Passive House, and not all those costs can be passed on to the client or the homeowner.

And then there are the perceived design limitations. Independent of those features I talked about, with regard to the consumer, the architects will find that they need to have simpler geometries. They have to do their floor plan layout so that most of the glass can face south. It’s also harder to do a Passive House with a basement than on a slab, so that’s a perceived design limitation. The cheapest way to insulate the attic is to put a couple feet of cellulose up in there, which means there’s no pull-down stair. So you start eliminating the storage in the basement and the storage in the attic, and there’s resistance both from architects and homeowners.

Rohracher: Many of these issues were also barriers to adoption in Europe. Many of them still are. And many of them you can work around.

For example, more than half of the Passive Houses in Europe have basements—you just have to change the design to decouple them firmly from the rest of the building. You need more collaboration between the different building professionals, because a Passive House is a much more tightly coupled technical system than a normal house. You have to integrate all building professionals into the planning process, and there needs to be a specific level of competence among all the different participants in construction.

Europe also has the same problems and issues in terms of uses and usage perception. Aesthetic quality is still an issue in Austria. It was so very important to show that you can make very good architecture and still meet the energy-efficiency standards. The proponents of Passive Houses would say that great architecture always comes from working with or against certain resistances and limitations.

Do we have to wait for U.S. manufacturers and suppliers to catch up to have access to Passive House building components and materials? Or can we work with what’s already available in Europe?

Rohracher: As Paul said before, it’s not just a matter of availability in the U.S. You have the technology, but it’s not widely available. And you do have not the same range of options seen in Europe. It’s something that will develop along with demand, I think.

Eldrenkamp: For some projects, people were actually shipping windows over from Germany because they were able to do that more cost-effectively than to buy North American triple-glazed windows.

But North American manufacturers are starting to respond. There’s a handful of window manufacturers now making windows efficient enough to meet the Passive House standard. A company in New Hampshire is starting to import Swiss mechanical systems and switching over the controls, so that you can use this Swiss equipment in the United States. You could normally do that with HVAC equipment because Europe is on 50 cycles a second, whereas the U.S. is on 60 cycles a second.

It's only a matter of time: The U.S. can build anything it puts its mind to. It just needs to put its mind to it.

Top photo: Mountain Retreat Schiestlhaus, Hochschwab. Robert Freund, ÖGUT.

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