The Passivhaus Institute (or Passive House Institute), located in Germany, has been pioneering the most energy efficient buildings in the world since the early nineties. Buildings certified to the Passivhaus standard are ultra-low energy buildings requiring very little energy for space heating.
For European passive construction, a building must meet the following requirements:
- Total primary energy use for all appliances, domestic hot water and space heating and cooling less than 120 kWh/m2.
- Total energy demand for space heating less than 15 kWh/m2 per year
A few comments to help qualify the figures above:
- An average home in Canada consumes 0.93 GJ/m2 or 258 kWh/m2 per yr
- Space heating in Canadian homes utilizes the most energy in the residential sector and accounted for 60% of the total residential energy consumed in 2005, or approximately 163 kWh/m2 per household per yr
There are over 6,000 certified Passivhaus’ in Germany, Austria and Switzerland. These houses use on average 85% less energy than comparable North American structures and far surpass even LEED Standards. And contrary to what you may think, these homes are as solid and durable as ordinary houses, brilliantly full of light and air, and comfortable. In fact, the Passivhaus mandate is that these buildings should be well known as the most comfortable homes in any region within all climates.
You may be asking: “Is it really reasonable to be comparing European standards to Canadian buildings considering the greater heating demand in our cold climate?”. My answer is YES, but also NO.
YES because there is no reason that we cannot incorporate sound and demonstrated methods and building techniques into our buildings to substantially increase energy efficiency, decrease losses and take full advantage of solar gains (i.e. free energy).
NO because it would be unwise to copy direct details from the Central European examples to other parts of the World. The Passivhaus concept must be first adapted for the climate under consideration.
Before discussing whether this could be done, I need to first describe how the impressively low energy demand is achieved.
The key elements of a Passivhaus include:
- Superinsulation: very high insulation to reduce heat transfer through walls, roof and floor is achieved using technologies such as Vaccum Insulated Panels and construction methods to minimize thermal bridges. The resulting U-value is between 0.1 – 0.15 W/m2/ºC.
- Passive Solar: planned and well thought out utilisation of solar and internal gains using compact shapes and windows oriented towards the south to maximize solar gain.
- Excellent air tightness: Air barriers and careful sealing minimizes the amount of warm air that can pass through the structure.
- Superwindows: Thermally efficient windows and frames with a U-value less than 0.8 W/m2/ºC. This very low window U-value is achieved by an intricately designed frame that minimizes thermal bridging. The triple glazing utilizes low-e coatings and inert gas filled air spaces to reduce radiative and convective losses. Because of the very low U-value and the high transmittance the windows can actually be considered thermal appliances as they provide more thermal gain than loss through the course of the year! It?s hard to believe, but true.
- Heating Load: All of these elements combined in the Passivhaus result in the energy efficiency being radically increased and the heat demand dramatically reduced. In fact, the peak heating demand in a Passivhaus is less than 10 W/m2.
[Comments from K.Klingenberg: 10 Watt/m2 and year: not true that this is the case independent of climate. it works out almost perfectly in Germany and Austria. Here in Illinois for example we meet the 15 kWh/sm and year, but the heat load is up to 16. That means that we need additional heat sources in the house, which is not a big deal. The initial requirement of 10 was recently turned into a recommendation by Wolfgang Feist and the PHI. We have learned that in very severe climates it is almost impossible to meet the 10, but it is still possible to make the annual 15 which is really the more important criteria since it is defines the overall consumption.]
With this low a heating demand, the ventilation system can easily be used for space heating and a separate heating system (i.e. boiler, natural gas furnace, forced air heating, electric baseboards, etc) is not required- regardless of the climatic conditions. Essentially, an advanced heat recovery ventilation system is used to recover and disperse heat while maintaining air quality.
Alright, to qualify some of the values that I?ve been throwing out, lets compare again to Canadian houses:
- Insulation: An R22 building (house with 2×6 wall construction) has a wall insulation U-value of 0.26 W/m2/ºC. Older homes in Canada built with 2×4 wall construction have an R value of 12, assuming fiberglass batt insulation. This is equivalent to a U-value of 0.47 W/m2/ºC (As compared to 0.1 ? 0.15 W/m2/ºC for a Passivhaus).
- Solar Gains: Few new homes in Canada are built taking into consideration passive solar gains and the ?free? energy available from the sun.
- Air Tightness: Construction standards for air tightness allow for 20 times more air leakage than allowed in a certified Passivhaus.
- Windows: A double pane window found in many typical Canadian homes has a U-value of approximately 2.5 W/m2/ºC. The best triple glaze, inert gas filled with low-emisivity coating that we could find in North American had a U-value of 1.77 W/ m2/ºC (as compared to 0.8W/m2/ºC).
- Heating Load: The resulting typical values for heating load range from 40-120 W/m2 (as compared to 10 W/m2).
The energy differences are staggering. The first big questions is: “What about the cost?”. In Germany, where most passive houses have been built, it has been published that with careful design and the increasing competition in the supply of specifically designed Passivhaus products (windows, wall materials, etc), it is now possible to construct buildings for the same cost as those built to normal German building standards. This is largely due to the cost savings from not having to incorporate a conventional heating system. However, we’ve also found reports of Passive Houses requiring an additional 40% investment. What is most important to consider of course, is not necessarily investment, but economics and energy autonomy. Considering that the peak heating load has been reduced to 10 W/m2 compared to an average assumed heating load of 75 W/m2 you can see that the energy savings on a monthly basis would be substantial.
[Comments from K.Klingenberg: The price per sqft (conditioned actual living and floor area), construction budget only, is currrently $120. If you take the footprint incl. the thick passive house walls, as the appraisers do here, it is $100. That is not bad at all. Locally, $110-$125 is the price per sqft for an ICF house advertised as being very energy efficient, but still uses 50% (compared to PH 10%) of heating energy. Our local construction prices are relatively low as you might have noticed.]
The second big question is: Is it possible, in Canada, to incorporate passive house technologies and construction methods and actually achieve a heating load comparable to passive houses in Europe considering that Germany, Austria and Switzerland generally have a milder climate than we do? Well, although there is not one certified Passivhaus in Canada to date- we think that this trend is coming. Now considered a mature technology in Central Europe, Passivhaus’ are being built in Poland, a passive apartment building in Sweden completed in 2006, and more than 15 passive house projects are currently in the planning phase in Norway. The Norway projects range from mild coastal to cold inland climates between 58º and 70º degrees latitude. Lastly, the first certified Passivhaus building in North America, the Waldsee Biohaus, located in Minnesota, was completed spring 2007. In terms of climate design criteria, Minnesota has a heating design temperature of -26ºC, latitude of 47.5ºC and annual degree-days of 5056. Calgary has a heating design temperature of -26.2ºC, latitude of 51º and annual degree-days of 5135.
[Comments from K. Klingeberb: I built the first passive house in 2003 (in Urbana, Illinois). Dr. Feist (Founder and Director of the Passivhaus Institute in Darmstadt, Germany) calculated it himself when I was at the PHI. I did not feel the need to get it certified because of that. The certification is also pricy and back then building the first prototype that was not in the budget. I started to promote, implement passive houses through our non-profit e-co lab, which is currently finishing up the third passive house here in Urbana and we will break ground next month on the 4th one. This makes e-co lab currently the leading passive house builder in the US. As e-co lab we have consulted on a Passive House project in Berkeley California, which is now nearing completion. Another project we are consulting on is a Martha’s Vineyard project that is going for certification with the PHI (2nd certified PH in the States). It broke ground in September.]
We also found on the internet, a fairly new company based out of Kelowna, British Columbia, Global Passive House. They indicated on their website plans to utilize intergrated Passive House standard building systems in a newly proposed Ecovillage on the outskirts of Kelowna. Also, Passive House Institute US has recently been formed in order to bring these standards, technology and innovations to the North American market.
One other thing worth mention is the Canadian Net-Zero Energy Home Coalition. A net-zero energy home supplies to the grid an annual output of electricity that is equal to the amount of power purchased from the grid. This is a somewhat different concept than Passivhaus, but many of the same design principles could apply.
Rising energy costs, peak oil, greenhouse gas emissions and climate change will demand that we cure our wasteful use of non-renewable resources. The technology exists to build super-efficient buildings achieving dramatic increases in resource productivity and superior air quality and comfort. Although disappointingly behind Europe in energy efficient design of buildings we can turn this into an opportunity to start with already proven and tested techniques and have greater confidence in our own ability to meet the challenge.
We are very much looking forward to one day visiting the first certified Passivhaus in Canada…. on the other hand, it may be ours!
[Comments from K. Klingenberg regarding the availability of superinsulated windows and walls in North America:
Our last passive house was built out of prefabbed panels (see www.e-colab.org) which allowed us to secure quality in the shop, implement details that already take airtightness into account and make it easier on site and best of all, it brought the price down dramatically.For our homes we did only import the very first heat recovery ventilator, after that we found materials and equipment on the local market (We have been using the Canadian Thermotech fiberglass windows. They are very close in performance to the German windows).]
I agree that the potential for making use of passive solar gain in Canada is vastly underutilized, and that the Passive House initiative is making a much needed statement in house design. My questions are where these low-thermal bridging walls and inert gas windows are made, and if they can be made with local regional materials and skillbases in a low-carbon future.