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.
The 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.
Houses
built to Passivhaus standards can be heated or cooled with the
energy it takes to operate a hand-held hair dryer.
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.
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.
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.
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/m² per year in
heating and cooling energy.
-
Total energy consumption must not be more than 42 kWh/m² per
year.
-
Total primary energy consumption (including heating, hot
water and electricity) must not be more than 120 kWh/m² per year. (Primary
energy is that contained in raw fuels and other forms of energy received as
an input by a system.)
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)
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. It will be featured in a future issue of Natural Life Magazine.
Rolf Priesnitz is the Publisher of Natural Life
Magazine, and also has over 40 years experience in the construction industry.
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