Passive House
It is our opinion that “Passivhaus” design generally makes ultimate sense philosophically, strategically, and in the relatively short term, financially.
The “Passivhaus” or passive house standard, like LEED in North America, has gained widespread popularity in Europe in recent years, and has in fact become the leading sustainable design standard on the continent with almost 20,000 residential, commercial and institutional units completed. The standard is open to almost every building type and currently quickly spreading throughout the world with projects in Russia, China, Japan, USA and Canada. Generally it is also possible to renovate a building to meet the passive house requirements but depending on the circumstances it will not always be feasible.
Probably the most important ancestor of the today’s passive house is the Saskatchewan Conservation House in Regina, build in 1977 by William Shurcliff and his team. Eleven years after William Shurcliff’s landmark press release, a German physicist, Dr. Wolfgang Feist, adopted Shurcliff’s list, suggested a few further specifications, and coined a German word, “Passivhaus”, to describe the construction method.
Unlike LEED, the passive house standard primarily focuses on reducing the long term energy consumption of the building, by reducing the heating and cooling demand to a near zero level. Usually roughly 85% of the environmental impact of a building over its lifetime is caused by its energy consumption; therefore reducing the energy consumption is becoming priority number one. With the passive house approach the energy consumption is decreased radically and at the same time the internal thermal comfort is significantly increased. To achieve this, emphasis is given to the quality of the envelope and the orientation for optimization of solar gain and avoids overheating, hence the term passive house. To realize this, the envelope needs to perform at a very high level thermally, be as air-tight as possible and be essentially free of heat-bridges.
A passive house consumes only about 10% of the heating and cooling energy of a standard Canadian commercial or institutional building. Once the energy demand is reduced to such low levels, practical opportunities for the use of alternative energy sources multiply, and the size of the mechanical system is to a great extent decreased. This said, the mechanical system must be designed to take advantage of the building’s efficiency and provide adequate ventilation and a very efficient heat recovery system.
Specifically, the passive house standard requires that the building fulfill the following requirements:
- The building must not use more than 15 kWh/m² per year in heating energy.
- The building must not leak air at more than 0.6 house volume per hour (n50 ≤ 0.6/hour), when de-pressurized to 50 Pa (N/m²) below atmospheric pressure by a blower door apparatus.
- The total energy consumption (energy for heating, hot water and electricity) shall not exceed 33 kWh/m² per year.
- The total primary energy consumption (primary energy for heating, hot water and electricity) must not exceed 120 kWh/m² per year (be aware of factor for energy source).
- The specific heat load for the heating source at design temperature is recommended to be less than 10 Wm².
From an energy point of view, the standard is up to 10 times more stringent than the levels currently achieved in standard construction in North America, and generally far exceeds the energy savings achieved under a LEED Platinum standard. The passive house concept and its technology is essentially the precondition to achieving a “net zero” building. In essence, a passive house with a small renewable energy generating system would qualify as a “net zero” building and could be truly carbon neutral.
In addition to the energy savings, a passive house design results in the equivalent of a climatic spa, as all interior surfaces are equally warm and generate symmetrical radiation temperatures. The air quality is also improved, as the air flow is very low and dust, soot and insects will be kept outside. The interior climate is simply healthy, very comfortable and generates wellbeing.
- With a combination of LEED Gold or Platinum and the passive house standard we will enter a new era of sustainable design.