While still living in Sweden, I heard about these incredibly energy efficient “Passive Houses”. On average, their annual energy consumption is about 90% LESS than a normal, drafty, comparatively poorly built abode. This is, of course, a staggering slap in the smug face of the construction industry and its code-writing officials, at the same time as it is wondrously exhilarating and totally punk rock progressive in terms of the concept of what our collective responsibilities should be, toward ensuring a future quality earthly existence for all. Since – according to the U.S. Energy Information Administration – “our buildings consume nearly half of the energy produced in the U.S., and are responsible for nearly half of the nation’s carbon dioxide emissions” – buildings like this are a BIG DEAL! Dare to imagine what we could accomplish if our building codes were written so that these houses were the norm rather than the exception… Climate change would slow down significantly if we were to change the rules today, and not allow any grandfather clauses. Dream on, dear readers…
According to Wikipedia, the Passive House standard emerged from a conversation between Professors Bo Adamsson of Lund University in Sweden, and Wolfgang Feist of Institut für Wohnen und Umwelt (Institute for Housing and the Environment) in Germany in May, 1988. By 2003, the idea had spread to the US, where the first Passive House was built in Urbana, IL. By now, there are an estimated 15 – 20,000 Passive Houses around the world, most of them in Germany or Scandinavia.
Now, fast-forward to the proud city of Cleveland, OH. Cleveland, despite a rich cultural history and many worthy attractions, still enjoys the reputation of a “post-industrial shit hole where the river caught on fire, not once, but TWICE.”. Sadly, in terms of sustainable thinking and progressive ideas, the area’s environmental policies have traditionally been the poster child of outdated patterns of consumption and cheerful, mindless wasting of resources. During our brief stay there in 2004, the wealthy eastern suburbs didn’t even have recycling programs in place! We were horrified, as we had just returned from living in Sweden – a country where the simple concept of Refuse, Reuse, Recycle is as natural as breast milk and part of the national conscience. So, imagine my astonishment when, on a visit to Cleveland this past summer, I stumbled upon the first Passive House I’ve ever seen in my entire life! Temporarily erected just outside the Museum of Natural History, was this marvelously energy efficient house, open to the public – just waiting to be visited, admired and explored. I was giddy with excitement! It was built with the intention to promote sustainable building to the residents and businesses of Northeast Ohio. After the exhibit, it was to be sold, and moved to its permanent location at the edge of University Circle – a traditional Cleveland neighborhood. (This fact explains this particular Passive House’s traditional looks.)
The most unusual, and initially startling fact about a Passive House, is that it has NO conventional furnace or heating system. It doesn’t need one! Its primary source of heating is its inhabitants and their appliances. The house is so extremely air-tight that that’s all it needs. How awesome is THAT!?! Some of you might recall that the first passive solar houses of the 1970’s had problems with mold and moisture build-up because they were so air-tight. This is not a problem here. Technology has come a l-o-n-g way since then. To ensure proper ventilation and prevent unhealthy moisture accumulation, a Passive House has lungs in form of an energy-recovering ventilation system and an air-source heat pump that provides an continuous flow of fresh, filtered air at a constant level of humidity. There are no sources of combustion (= pollutants and carbon monoxide production) in the house, and walls are designed and constructed to keep excessive moisture at bay.
There are several design principles that sets a Passive House apart from the norm. One of them is the airtight construction. A drafty old house might have as many as 20 involuntary air changes per hour. A drafty house of newer construction might come in at about 3-6. The building envelope cradling a Passive Home performs at a stunning rate of less than 0.6 air changes per hour as measured by a pressurized blower door test. All seams and holes in the building envelope are meticulously sealed, and the continuous air barrier that runs throughout the building enclosure is located in the center of the wall, where the risk for accidental rips and punctures is minimal.
A Passive House strives to minimize temperature conductivity through its walls by eliminating so called thermal bridges. A thermal bridge occurs wherever poorly insulating materials (metal, concrete etc.) bridge the distance between interior and exterior. No matter how much insulation surrounds this continuous bridge, heat and cold will travel unhindered along it, and thwart any attempt at temperature containment, as it acts as a temperature super-highway between in and out. A well constructed wall makes use of thermal breaks, where good insulators separate the more conductive materials – thus slowing down the rate of heat transfer. The walls of a Passive House are over a foot thick, and use foam and cellulose to create a super-insulated barrier, sporting an insulation value of R-50. To put this number in perspective, it is interesting to know that Ohio building codes only require exterior walls to have a piddly R-13!
Add to this high-performing, triple-pane argon casement windows and you get a very comfortable, quiet interior. We were there a few days after July 4th, and were told that the commotion of the parade that passed by right outside the glass front door of the house, could hardly be heard on the interior! But, the most noticeable of all was that despite outside temperatures in the high 90’s, the interior was wonderfully cool and pleasant, even on the second floor. These windows have an R-value of 11, which means that they almost meet the Ohio code for walls! Really – this ought to be down-right embarrassing to the reactionary crackpots who pen those codes…
The shape of the building also matters. It’s that old ratio of surface area to volume that’s at work here, and along with basic considerations like optimal siting in regards to solar gain, this is the place to start the planning of a Passive House. Consequently, the absolute best would be a spherical house, but considering the shape of most building materials, it has to be concluded that anything close to a boxy square or a chubby rectangle would have to be deemed good enough. It certainly will be much easier and cost effective to build! The aforementioned ventilation system recycles heat with an 84% efficiency as it transfers the heat of the outgoing air to the fresh, incoming air. In order to weather the long, cold Cleveland winters, this house was also equipped with a small, ductless air source heat pump, which does double duty providing supplementary cooling during the hot, muggy Midwest summers. Compared to a conventional furnace, the energy required to run the heat pump is negligible. Lastly, it goes without saying that nothing less than Energy Star appliances and LED lighting would be considered here. Why ruin a good thing with anything else… right?
What does all this cost? Offsite pre-fabrication and modular components help keep prices down, and the final price tag is surprisingly affordable. On average, a Passive House costs around 14% more than a conventionally built house. Mind you, this number is said to increase significantly at latitudes north of 60° (think Helsinki). Either way, at today’s soaring energy costs – considering what you will be saving in the long run, a house like this will probably owe you money some day, before too long! With such a low energy use to begin with, the upgrade to a net-zero house is very much within reach. In the PNC SmartHome in Cleveland, this additional perk was illustrated by an adjustable solar panel which, like a sunflower, moves with the sun and captures up to 40% more solar rays than stationary units. In the spirit of the project, the exhibitors also incorporated rain water harvesting systems, a native garden, reclaimed and repurposed wood, etc.
So, how does the “green-ness” of a Passive House certification compare to, say, the U.S. Green Building Council’s various LEED (Leadership in Energy and Environmental Design) certifications, a Living Building Challenge, or any of the other green building certification systems? PHIUS – the organization that issued the certification to this house, and others built in the U.S. – requires:
1) Energy use for both heating and cooling must be less than 15 kWh/m²/year (4,755 Btu/ft²/year).
2) Total primary energy use must be less than 120 kWh/m²/year (38,000 Btu/ft²/year) for all energy needs (including lighting, water heating and appliances).
3) Air leakage must be less than 0.6 air changes per hour at 50 pascals of pressure difference between the interior and exterior (0.6 ACH50). This is measured by a blower door test.
As you can see by the three stated requirements above, the Passive House philosophy concerns itself primarily with energy performance. The LEED certification has a more broad-spectrum approach, incorporating anything from building site location, nearness to public transportation, life cycle impact of materials, indoor air quality, landscaping, etc. The Living Building Challenge is in a class by itself, as it requires total self reliance regarding both energy and water, demands locally sourced building materials from within a set geographical radius, and strict commitment to the avoidance of any “red-listed” toxic ingredients. Having just emerged from a Living Building Challenge when I saw the Cleveland Passive House, I was puzzled by certain material choices that had been made – notably the use of EPS (expanded polystyrene) foam insulation and vinyl fencing, which I perceived as a blemish on their green commitment. In a Living Building Challenge, both of these would be on the “Red List”, meaning very unhealthy for both humans and environment. Although EPS obviously is a highly efficient insulator, I wonder how many years the inhabitants of the house have to inhale its fumes. Perhaps this was the reason that, in this case, the EPS panels were placed on the outside of the exterior wall – on the exterior side of the continuous air barrier?
In August of 2011, there was a bit of a blow-up between PHI (the Passive House Institute), and PHIUS (its American partner). According to the Jetson Green blog, the rift had to do with several matters:
“1 )PHIUS allegedly certified Passive House Buildings without the requisite documentation, thus threatening the integrity of the standard.
2)PHIUS allegedly infringed the Passivhaus Institut’s copyright in the PHPP software by selling and making changes to it without authorization or license.
3)PHIUS introduced a competing professional certification scheme and allegedly refused to honor existing contractual obligations with the Passivhaus Institut.”
Sad as contractual disruptions and philosophical frictions are, I ask myself if I really care. The answer is no. I really don’t. My highly personal opinion regarding certifications are that while they may serve to rally allegiance around certain issues, and – upon project completion – provides an excellent marketing tool as well as a shiny new feather in the hats of the people that made it happen, they really don’t matter at all. What truly matters is that a real effort to build better, healthier, safer, and with focus on sustainability and environmental responsibility, was made. I can’t help but think of the various certifications as a kind of territorial pissing contest. There – I’ve said it! I think the important thing is that we all do our best – opt for longterm benefits, embrace sustainable technologies, and strive to optimize the way we use and reuse our dwindling resources. How we do it is less important, as long as we do it, but I think a good start would be to up the ante on the building industry by increasing code requirements throughout the world, but in particular here in the U.S. The new requirements should come combined with economic incentives in the shape of more tax rebates, and more accessible, cheap energy loans for home owners – both for new construction and retrofits. In the face of looming planetary adversity, a certification more or less isn’t going to mean a damn thing! The fact that there were enough progressive minds in stodgy old Cleveland to successfully pull off a project like this, filled my heart with joy. If they can do it in Cleveland, most surely there is hope for the rest of us… 2012 – here we come! Let’s make a difference!