In writing the 2012 Seattle Energy Code, the Seattle Code Committee did something that is perhaps unprecedented in the history of municipal regulations.
Namely, the new code included a path to compliance that would allow developers to essentially do anything they wanted to a building, so long as the building plans met a few simple prerequisites and a strictly-defined energy performance target. This is a provision that provided developers with a unique degree of flexibility, while also giving the city real leverage in mandating energy efficiency.
While this new compliance path in Seattle is optional (there are three other paths that design teams can use to comply with the code), it represents a shift in energy policy that is truly groundbreaking in America. This alternate compliance path is one of the first true “performance-based” codes in the country, and it represents a glimpse of the future.
Quite frankly, the modern construction industry evolved during a time when high performance wasn’t required in the built environment.
That time, however, is passing.
All about Passive-House
Recently, a movement called “Passive-House” has been proudly on the front lines of understanding and experimenting with performance-based codes.
Simply put, Passive-House (also “Passivhaus” or “Passive House”) is a performance-based certification for buildings that was formalized in Germany in the early 1990s. Unlike green building certifications such as LEED (which primarily relies on a checklist of mandatory actions), the most recent iteration of the Passive-House standard certification focuses primarily on meeting three measurable performance factors:
- Peak instantaneous energy use for heating and cooling energy use per square foot of building area
- Total annual energy use per occupant
- Total building air tightness
With Passive-House, heating and cooling energy targets are tailored to the climate of the site location, and the annual energy use target also considers the carbon intensity of the energy source. This makes it harder to meet the target if you have carbon-intensive power, like coal fired electricity.
More than 20,000 buildings have been certified since the first iteration of Passive-House in Germany, and Passive-House is now used as the code minimum for construction in several European countries: Belgium, Luxembourg, and Austria.
Since 2001, certification and public awareness in the U.S. has largely been driven by the Passive House Institute U.S. (PHIUS). PHIUS has certified more than 120 buildings, held annual conferences since 2006, and trained more than 1,700 architects, engineers, energy consultants, energy raters, and builders in how to meet the stringent certification criteria.
As with any certification, Passive-House has drawn plenty of criticism. However, it stands as the first performance-based building certification to garner significant popularity in the United States.
To date, PHIUS has primarily focused on residential construction, thus limiting its potential impact. While a few examples of commercial multi-family and office building Passive-House projects are now making waves in the marketplace, designers still face significant barriers to widespread commercial adoption—including architectural proclivities, cost-effectiveness concerns, and limited availability of materials & equipment suitable for Passive-House.
As explained by PHIUS, meeting the performance-based standards of Passive-House certification is primarily dependent on following five proven strategies:
- The building employs continuous insulation through its entire envelope without any thermal bridging
- The building envelope is extremely airtight, preventing infiltration of outside air and loss of conditioned air
- It employs high-performance windows (typically triple-paned) and doors
- It uses some form of balanced heat & moisture-recovery ventilation and uses a minimal space conditioning system
- Solar gain is managed to exploit the sun’s energy for heating purposes and to minimize it in cooling seasons
Each strategy is designed to deliver energy efficiency, comfort, and long term building durability—all of which contribute to the value experienced by the owner. Each strategy also represents a challenge for designers and contractors. To wit, high-performance windows can be expensive and require long lead times while ventilation requirements can stymie commercial exhaust systems.
Aside from these challenges, energy codes on the local, state, and federal level are undeniably shifting from a prescriptive approach to a performance-based approach. Passive-House standards are the ultimate performance-based standards and have a demonstrable track record.
Why Passive-House matters
Many in the construction industry pay lip service to energy efficiency, but performance-based codes are the only real way to achieve the radical level of energy-efficiency which will be necessary both to differentiate buildings in the marketplace and appropriately respond to climate change goals.
While all buildings won’t be transforming into passive buildings overnight, owners, designers, and construction workers would be well-advised to learn about Passive-House standards as a primer in delivering on performance-based codes.
At McKinstry, our clients expect us to guide them through new regulations and present an actionable vision for how to keep their buildings on the cutting edge of sustainability and market viability.
Multi-pronged construction firms like McKinstry can, should, and will play an important role in bridging the gap between the current standards for the built environment and the dynamic possibilities and challenges that will arrive with implementation of performance-based codes.
Skander Spies is a Seattle-based project engineer for McKinstry and a Certified Passive House Consultant (CPHC). He can be reached at firstname.lastname@example.org.