Friday, June 05, 2020

Passive House vs LEED - which is best?

As Canada belatedly joins in with the Passive House movement, it comes head to head with the Leadership in Energy and Environmental Design (LEED) standard developed by the Green Building Council of the USA and Canada. Both are standards, or certification systems, developed as a way of certifying architecture that aspires to environmental principles, particularly sustainable, low/no carbon buildings.
The Passive House standard was originally developed in Germany (Passivhaus) in the 1990, although many of its principles go back further to the 1970s. It's pedigree is therefore longer, and it is showcased by a great many more buildings, mainly in northern Europe (Germany, Denmark, Netherlands, etc).
Passive houses are designed to stay at a comfortable temperature without "active" heating and cooling from furnaces and air conditioners, utilizing a variety of techniques from passive sunshine to heat from pipes to the body heat of the occupants, incorporating efficient orientation, air-tight, draught-free, ultra-efficient doors and windows, heavy insulation and triple-glazing, mechanical ventilation systems that capture and release heat as needed from air entering and leaving the building, and eliminating materials and structures that transfer heat between the interior and exterior of the building (e.g. fibre glass clips instead of metal screws to attach external siding). Often, they also incoprorate renewable energy, such as from solar or geothermal sources, which can make them net negative carbon contributors.
Over 2,000 passive house buildings have already been built in Canada, most over the last few years, and many of the new crop of buildings under development here are looking to scale up the traditional passive house ideas to larger buildings, high rises, etc.
So, how is this different from the more familiar North American LEED system? Under LEED, which has various levels of compliance (unlike Passive House, which is more of an all-or-nothing proposition), builders aim to increase their "score" by adding elements that the Green Building Council recommends, such as energy efficiency, water efficiency, location, materials, green roofs, and even a category called "awareness and education". Since 2004, LEED has certified over 4,350 buildings in Canada, and registered over twice that number, giving Canada the second highest number of LEED projects in the world.
Some low/no-carbon architecture purists argue that Passive House is a more rigorous and superior standard, and that LEED devotees are merely "chasing a checklist". But even they would admit that LEED has done a good job of branding the concept of environmentally-sustainable architecture, and bringing the sustainability conversation into the mainstream of architectural practice.
Probably both camps would agree that buildings that meet both standards would be the ideal aspiration to aim for.

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