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Buying or Building Your Sustainable Home
Passive Houses - Passivhaus
by Rolf Priesnitz

In this column in the November/December 2009 issue of Natural Life Magazine, I noted that the Green Building Council’s Leadership in Energy and Environmental Design (LEED) is no longer the only standard for sustainable building. After being part of the construction industry for over forty years, I am thrilled that their leadership has resulted in a variety of green building standards that are also capturing the attention of builders and the public. I’ll be outlining some of them in this and future columns.

As I mentioned last time, one of the problems I see with many of the demonstration projects that are popping up is their reliance on technology to the degree that they often ignore the more obvious low-tech solutions. Those include awnings, natural ventilation, minimal windows facing away from the sun, buffering landscaping, clotheslines and so on.

One of the newly emerging building concepts that addresses that issue is the Passivhaus movement, an exciting European building design program that offers tremendous energy savings – as much as ninety percent – due to reliance on passive heating systems and good sustainable design. The claim is that houses built to Passivhaus standards can be heated or cooled with the energy it takes to operate a hand-held hair dryer.

PassivhausThe first Passivhaus buildings were built in Darmstadt, Germany in the early 1990s. In 1996, the Passivhaus Institut was founded in Darmstadt by German physicist Dr. Wolfgang Feist to create, promote, and control the standard. There are an estimated fifteen thousand houses already built in Europe to this standard. Feist drew inspiration from a number of pioneering buildings from the 1970s, including the Lo-Cal house developed by researchers at the University of Illinois in 1976, the Saskatchewan Conservation House completed in 1977 (featured in Natural Life Magazine in our second year of publishing), and the Gene Leger house built in 1977 in Pepperell, Massachusetts.

Surprisingly, it took until 2008 for the concept to come to North America.  The Passive House Institute US (PHIUS) was formed in 2008 to address the U.S. building market and to develop and test standards for North American climate conditions. For instance, Alberta would require additional insulation levels and, in warm climates like Florida, cooling becomes the major factor in energy usage. In more humid climates, dehumidification becomes an issue in designing a Passivhaus. The first certified Passivhaus in North America was built in northern Minnesota in 2006, although a few were built in Illinois to the standard and not certified.

The Passivhaus movement likes to define a passive house as a fundamental design concept rather than a rigid energy performance standard. A Passivhaus is super-insulated and virtually air-tight. Typically, it will use a variety of methods such as strategic window placement and triple pane double low-e glazing and shading. Special attention is given to eliminating thermal bridges, which are created when building materials that are poor insulators (such as electrical sockets, lintels, radiator enclosures, parapets, reinforced concrete pillars, window sills) create “bridges” that allow heat to leak.

The Passivhaus does not need a traditional heating or cooling system and is, instead, heated by well-thought out passive solar gains and by the heat given off by people, electrical equipment, hot water and so on. A whole house mechanical ventilation system allows the exhausted air to be used to heat or cool fresh incoming air while maintaining good indoor air quality. Using a geothermal system to cool or warm air by forcing it through earth-buried ducts provides an additional heat source and opportunity to increase the efficiency of the ventilation system.

In areas of extreme temperatures, designing thermal storage mass into the building is important. To this end, the designer will specify features such as tile floors, finished concrete slabs, concrete or granite countertops, stone fireplace surrounds, adobe walls or earthen plaster.

Some designers utilize solar hot water systems in addition to the passive house construction techniques, since domestic hot water is the second biggest energy requirement in a home, next to space heating/cooling. The system can serve a dual purpose, with the hydronic heating coil integrated into the ventilation system to provide extra space heat where required.
Houses built to Passivhaus standards can be heated or cooled with the energy it takes to operate a hand-held hair dryer.

The specifics required to meet the Passivhaus certification vary, depending upon the climate. They are generated and verified at the design stage using what’s called the Passivhaus Planning Package, a software suite that projects heat load, heat loss and energy usage for a specific building. Also, a quality control procedure is required in order to avoid onsite problems that could prevent optimum levels of airtightness and thermal insulation being achieved.

One of the things I like about the Passivhaus system is the relative simplicity of its requirements, compared to many of the other green standards. Here, for instance, are the required performance characteristics for central Europe:

  • The building must not use more than 15 kWh/m per year in heating and cooling energy.

  • Total energy consumption must not be more than 42 kWh/m per year.

  • Total primary energy consumption (including heating, hot water and electricity) must not be more than 120 kWh/m per year. (Primary energy is that contained in raw fuels and other forms of energy received as an input by a system.)

The Passivhaus does not need a traditional heating or cooling system and is, instead, heated by well-thought out passive solar gains and by the heat given off by people, electrical equipment, hot water and so on.

So what about cost? At this time, PHIUS estimates an additional investment of approximately ten percent over a code-compliant home in the U.S. That relates mostly to the low availability and high cost of passive construction materials. Presumably, as the movement gathers steam in North America, the market for the required building components will grow and the prices come down. In Europe, passive houses tend to cost only about five percent more to build than conventional ones.

The additional up-front costs are, of course, more than offset by long-term energy cost savings. One of the criticisms I noted about LEED buildings is that much of their energy savings depends upon the actions of trained and interested occupants. A passivhaus, of course, doesn’t rely on active intervention by the homeowner, so it should be easier to maintain low energy usage on an ongoing basis.

Aside from cost, there are a few hurdles for Passivhaus builders to overcome in North America, including marketing and the good old American love of gadgetry. It remains to be seen if the Passivhaus standard will migrate well to a different climate and culture. But it’s definitely generating some interest. And it’s definitely an extremely green standard.

Learn More

Homes for a Changing Climate: Passive Houses in the U.S. by Katrin Klingenberg, Mike Kernagis, Mary James (Aspen Publishers, 2009)

An Award-Winning Affordable Passive House Design

Passivhaus Institut,  Darmstadt, Germany

Passive House Info in English

Passive House US Urbana, Illinois

Waldsee BioHaus Bemidji, Minnesota

Update: February, 2011 - Canada's first Passivhaus certified project has just been completed. A duplex in Ottawa by Vert Design Inc. that was destined for LEED certification has also met Passivhaus standards.

Rolf Priesnitz is the Publisher of Natural Life Magazine, and also has over 40 years experience in the construction industry.

 

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