The term ‘PassivHaus’ refers to a voluntary, ultra low-energy construction standard first developed over a decade ago by Dr Wolfgang Feist of the Passivhaus Institut Germany.
The objective of PassivHaus design is to reduce the requirement for spaceheating and cooling. This can be achieved without compromising comfort.
To achieve the PassivHaus standard the energy required for space heating must not exceed 15 kWh/square meter/year (1.4 KWh/square foot). To give you a sense of this, a 1500 square foot home achieving this standard would have an ANNUAL space heating bill of $51.45 (1500 sq feet*1.4KWh/square foot/year*$.0245/KWh for natural gas (in Saskatchewan, March , 1009))
Achieving a space heating requirement of 15 kWh/(m2 a) or less means that the following technologies are required:
• Super-insulation: opaque U-values must be less than 0.15 W/m2K (equivalent to greater than R 38
• U-values for windows and doors need to be 0.8 W/m2K or less (equivalent to R7 or more) for both the frame and glazing. This requires the window frame to incorporate insulation and triple glazing
• Thermal bridging needs to be minimised, and ideally eliminated. A thermal bridge is created when materials that are poor insulators come in contact, allowing heat to flow through the path created.
• Airtightness: n50 of 0.6 h-1 @ 50 Pa or less
• Whole house mechanical ventilation with heat recovery (75% efficient or better, with a low specific fan power).
I was blessed to have the opportunity to travel to Germany to study the PassivHaus Standard. Thanks to the efforts of Tom Keesey of our Foreign Affairs and International Trade Canada office in Saskatoon, I was able to meet with one of the engineers from the PassivHaus Institute in Darmstadt as well as three architects/builders that build PassivHaus construction in Germany.
As part of those meetings I toured over 20 PassivHaus homes at different levels of construction. The following are some of my observations about the construction of PassivHaus homes:
- A lot more time seems to be spent at the design phase with an incredible focus on eliminating thermal bridges and maintaining a continuous air seal throughout the building
- The Germans seem to be ahead of us in a lot of the technologies required for building low energy homes:
- Windows
- Air barrier systems
- HRV systems
- Alternative energy (the area around Frankfurt is heavily treed and they were investing in technologies for using wood pellets for space heating)
- One of the key roles of the PassivHaus Institute is to certify this equipment so builders can feel confident using them.
- The German construction industry seems to be more precise in their construction methods. On one home I saw, the construction manager was complaining about a foundation that was out by .5 centimers (less than ¼ inch).
- The German trades and sub-trades appear to be much more efficient. One of the builders I talked to spoke of labor rates for trades to be over 50 Euros (about $70) per hour yet their total cost of construction is 900 euros/Square meter or $120 per square foot.
- The entire industry seemed much better organized. One project manager I talked to was managing the construction of 29 homes at the same time. I asked another project manager about problems with sub-trades not showing up on time. She indicated that scheduling was not an issue and was only able to remember one sub-trade showing up 3-4 hours late about a month before. She thought it was because of an illness in the family.
Malcolm Isaacs, a Quebec based engineer is bringing the PassivHaus standard to Canada (see www.passivhaus.ca). It will be interesting to see how he does.
Malcolm is doing a good thing for the Canadian Residential Construction Industry. We can learn a lot from the design and construction practices I saw in Germany. The 15KWh/Square meter requirement is a very high standard that will result in significant energy and green house gas reductions. The requirement for mechanical ventilation results in much better air quality in the home.
Malcolm will have some challenges. It will be very difficult to meet he 15KWh/Square meter requirement in many areas of our country because of our colder climate. I am not sure we have the quality control in our current construction processes to achieve the required tolerances. We already have a number of standards in Canada and this may be confusing the public.
There are 15,000 PassivHaus homes in Europe. A typical 1800 square foot home in Saskatchewan uses about 200 KWh/square meter. If we could reduce that to 15KWh/Square meter in 15,000 homes in Saskatchewan that would be a total energy reduction of over 464,000,000 KWh of electricity per year. If these homes were using electric heat, that would reduce Green House Gas emissions by 385,000 tonnes per year. If they are using natural gas for heating the GHG emissions would be reduced by 104,000 tonnes. These houses will easily be around for 50 years or more. Total savings over 50 years would be 5.2 to 23.2 Megatonnes of GHG.
Now that would be something to be proud of…
