The basics of passive design and what they mean to the design-build community.
BY DOUGLAS WEINSTEIN
WE HAVE BEEN THROWING around the term ‘passive design’ for some time and I met a number of people at the Consumer Electronics Show in Las Vegas last week – some from the world of technology and some from the design-build community (kitchen and bath vendors, media, roulette pit bosses, etc.) – who asked about what actually comprises a passive design and why that’s important. So here’s a brief primer:
Passive building is a set of design principles used to attain a rigorous level of energy efficiency within a specific comfort zone. “Optimize your gains and losses based on climate” summarizes this approach. Passive building is designed and built in accordance with these five building-science principles:
- Employ continuous insulation throughout the entire building envelope without any thermal bridging.
- The building envelope is extremely airtight, preventing infiltration of outside air and loss of conditioned air.
- Employ high-performance windows (double or triple-paned windows depending on climate and building type) and doors. 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.
- Use some form of balanced heat and moisture recovery ventilation.
- Use a minimal space conditioning system.
Passive building principles can be applied to all building types – single-family residences to MDUs and commercial properties.
Passive design strategy 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 comfort even in extreme weather conditions.
- Continuous mechanical ventilation of fresh filtered air provides clean indoor air quality.
- Passive building principles offer a direct path to Net Zero and Net Positive buildings by minimizing the load that renewables are required to provide.
North American building scientists and builders with funding from the U.S. Department of Energy (DOE) and the Canadian government pioneered passive building principles in the 1970s. In the 1980s the German Passivhaus Institut (PHI) built on that research and those principles and developed a performance standard that continues to work well in the Central European climate zones.
However, a single standard for all 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 metrics you want to achieve, 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.
Passive homes create a more stable environment (as it relates to the home’s climate) due to the amount of insulation and airtight quality of the housing envelope. So you need less energy to maintain your preferred climate temperature, and you are better able to control your air intake (filtering to provide clean air) and air-scrubbing (removing the bad air).