Passive building comprises a set of design principles used to attain a quantifiable and rigorous level of energy efficiency within a specific quantifiable comfort level. “Maximize your gains, minimize your losses” summarizes the approach. To that end, a passive building is designed and built in accordance with these five building-science principles:
- Employs continuous insulation throughout its entire envelope without any thermal bridging.
- The building envelope is extremely airtight, preventing infiltration of outside air and loss of conditioned air.
- Employs high-performance windows (typically triple-paned) and doors.
- Uses some form of balanced heat- and moisture-recovery ventilation and a minimal space conditioning system.
- Solar gain is managed to exploit the sun's energy for heating purposes in the heating season and to minimize overheating during the cooling season.
Passive building principles can be applied to all building typologies – from single-family homes to multifamily apartment buildings, offices, and skyscrapers.
Passive design strategy carefully models and balances a comprehensive set of factors including heat emissions from appliances and occupants to keep the building at comfortable and consistent indoor temperatures throughout the heating and cooling seasons. As a result, passive buildings offer tremendous long-term benefits in addition to energy efficiency:
- Superinsulation and airtight construction provide unmatched comfort even in extreme weather conditions.
- Continuous mechanical ventilation of fresh filtered air provides superb indoor air quality.
- A comprehensive systems approach to modeling, design, and construction produces extremely resilient buildings.
- Passive building principles offer the best path to Net Zero and Net Positive buildings by minimizing the load that renewables are required to provide.
The Performance Standard
North American building scientists and builders with funding from the U.S. Department of Energy (DOE) and the Canadian government were the first to pioneer passive building principles in the 1970s. In the late 1980s the German Passivhaus Institut (PHI) built on that research and those principles and developed a quantifiable performance standard that continues to work well in the Central European and similar climate zones.
However in practice, the PHIUS Technical Committee, PHAUS members, and project teams building projects in North America learned that a single standard for all North American climate zones is unworkable. In some climates, meeting the standard is cost prohibitive, in other milder zones it's possible to hit the European standard while leaving substantial cost-effective energy savings unrealized.
As such, in cooperation with Building Science Corporation under a U.S. DOE Building America Grant, the PHIUS Technical Committee developed passive building standards that account for the broad range of climate conditions, market conditions, and other variables in North American climate zones. The result is the PHIUS+ 2015 Passive Building Standard – North America, which was released in March of 2015. Regardless of the metric, the principles are the same, and the passive building community is working hard to make this approach the mainstream best practice for building design and construction.