Building the Case for Passive House Standards

Insights on what’s next from the founder of the certification program in the U.S.

Passive house building principles have been around for a long while but humans, curious by nature, searched for new practices, created new materials and sought new designs, basically putting these (g)old practices on hold. Then, climate change took a turn for the worst, and passive house building methods became problem solvers.  

In the U.S., passive house building standards are increasingly popular, much like a long-lost and recently rediscovered treasure. Katrin Klingenberg is the co-founder & executive director of the Passive House Institute U.S. (Phius). An architect by formation, she built her own passive house in Urbana, Ill., in 2002, which sparked a lot of interest, encouraging her to launch the Community Housing Development Organization to develop affordable passive houses in partnership with the City of Urbana. From there on, founding Phius occurred naturally.

Over its 20-year history, Phius grew and revised its standard. Since 2015, it became a partner of the U.S. Department of Energy Zero Energy Ready Home (DOE ZERH) program and together have launched the first climate-specific passive building standard, providing designers and builders with cost-effective and ambitious carbon and energy reduction targets for their climate zones. Updates to the standard were released in both 2018—which accounted for building typology—and in 2021, when amendments focused on zero energy and electrification. More about the Phius standard from its launch to this day in the below interview with Klingenberg.

READ ALSO: How to Retrofit Value-Add Properties as Carbon-Neutral Assets

How does Phius differ from or complement other green building standards?

Katrin Klingenberg, Co-Founder & Executive Director, Phius. Image courtesy of Phius

Klingenberg: Green building standards such as LEED and the DOE ZERH program have successfully raised the floor when it comes to healthy construction, and Phius builds upon that foundation. These programs provide a baseline quality framework, and Phius builds upon that with passive-specific requirements such as airtightness and thermal comfort. This, along with required third-party quality assurance, ensures every Phius project performs up to energy efficiency expectations.

The DOE ZERH, Environmental Protection Agency (EPA) Indoor airPLUS, and EPA Energy Star programs are co-requisites for Phius certification, making the transition to Phius smoother for professionals who have experience with those programs.

How many U.S. projects are presently Phius-certified? What states/municipalities have adopted Phius as part of their energy codes?

Klingenberg: Phius has certified more than 640 projects in the U.S. and more than 7.4 million square feet of projects in total. Currently, four states—Massachusetts, New York, Illinois and Washington—and three major municipalities—Boulder, Denver and Chicago—have adopted Phius as part of their energy code. In a recent stretch code passed in Massachusetts, all residential buildings over 12,000 square feet are required to be passive house certified. Currently, 15 municipalities, including Boston—covering 20 percent of the state population—have adopted this new code.

Phius is also written into the Qualified Allocation Plan of 19 states, meaning developers earn points toward the low-income housing tax credit funding if they build to Phius standards.

What property type leads by number of Phius certifications? What share of the Phius portfolio is multifamily?

Klingenberg: Currently, 60.8 percent of Phius-certified projects are single-family homes, and 31.8 percent are multifamily buildings. However, in terms of total square footage, multifamily projects account for 68.9 percent, with single-family homes at 12.9 percent, mixed-use at 12.8 percent and commercial for the remainder (5.4 percent). Construction of Phius-certified multifamily projects has grown exponentially in the last few years as local and federal municipalities offer increasingly enticing incentives for developers.

Compared with conventional projects, how expensive is it to build to Phius standards?

Klingenberg: Based on data from a number of multifamily Phius projects, the upfront premium is often between 0 to 4 percent. This can vary based on the experience of the project team and a host of other factors, but Phius projects can be built at or near cost.

Tell us about a project that impressed you, sustainability-wise.

Klingenberg: It is almost impossible to choose just one, but the recently certified 425 Grand Concourse project in the Bronx, New York City, is truly one-of-a-kind. Aside from being the largest Phius-certified project to date, it was built by an affordable housing developer and has a multi-use base that serves as an anchor in its community. In addition to its housing units, the 26-story building contains a health clinic, educational facility, supermarket and community support space. It is the perfect model for the future of high-performance urban construction.

On the other end of the spectrum, there are so many beautiful, right-sized single-family homes now everywhere in the country. My own house, the first passive house built in the U.S. in 2002 in Urbana, stuns me still in how comfortable and quiet it is and how much it feels like living in harmony with one’s environment by ‘touching the earth lightly’ in terms of carbon footprint. And energy-wise, the building gives back. It truly is a positive energy home.

How does the Inflation Reduction Act impact Phius-certified projects?

Klingenberg: Thanks to Phius’ inclusion of federal programs such as the DOE ZERH program and EPA Energy Star, all projects that earn Phius certification are eligible to claim the tax credits through the Inflation Reduction Act. If a project is Phius-certified, it’s eligible for IRA funding.

What steps do multifamily developers need to take to benefit from the incentives offered by utility providers, local municipalities and the federal government through IRA?

Klingenberg: For utility incentives, developers can submit an application through the utility website. There is limited incentive funding so not every application is approved.

For single-family and multifamily buildings under five stories, Phius requires the project to achieve ZERH and Energy Star certifications as part of the overall certification. Since the 45L tax credit requires one of these certifications, achieving a Phius certification means developers are eligible to claim the tax credit.

Which are the biggest hurdles for green building to grow from trend to standard?

Klingenberg: Mass adoption of Phius and other green building standards will likely be policy-driven. Luckily, the issue of the built environment’s impact on climate change has grabbed the attention of policymakers in recent years, spurring positive momentum such as the IRA. One of the largest remaining hurdles is conveying to lawmakers that established programs such as Phius are viable options to be implemented as code in order to achieve climate goals.

What is next for Phius?

Klingenberg: We like to stay plenty busy at Phius, so there are several exciting developments on the horizon! The most noteworthy is PhiusCon 2023, our annual conference, which will take place November 7 to 10 in Houston. We’re excited to increase our footprint in the region and provide the thought-provoking keynotes and informative sessions that have made PhiusCon the top passive building conference in North America.

Additionally, we are working on a groundbreaking framework for retrofits that is slated to launch in 2024. With a focus on resilience and carbon accounting, it’s designed with mass-scale retrofitting in mind. We believe it will be instrumental in improving the health of our current building stock.

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