Zooming In on Phius, an Increasingly Popular Passive Building Certification

Zoe Rader discusses new standards for achieving net-zero buildings.

Zoe Rader of Phius
The Phius Standard is updated every three years to reflect market and materials changes and other variables, with the 2024 standard update to be rolled out this summer, said Rader. Image courtesy of Phius

Experts from various industries and policymakers—sharing the common goal of improving strategies for achieving net-zero energy buildings—met virtually at Phius Summit 2024 in mid-April.

The event emphasized the importance of integrated design approaches that consider climate resilience, equity and affordability, shared certification updates and highlighted the global impact of passive house principles. Sessions covered topics such as passive house design, energy-efficient construction materials and innovative HVAC systems.

Zoe Rader, a building certification associate and policy specialist at Phius who is also close to becoming a Phius Certified consultant, moderated the panels, so we asked her to share details about the topics discussed and the latest trends in passive building.


READ ALSO: Building the Case for Passive House Standards


Unfamiliarity, lack of experience and cost seem to be the main obstacles for Phius’ wider adoption. How is the organization tackling them?

Rader: Education is a big part of our efforts to familiarize the public with Phius and passive building. We recently launched the Passive Building Foundations training, which is a self-guided online training that introduces a variety of fundamental topics related to Phius and passive building. It is meant as an entryway into the world of passive building for those without backgrounds in architecture or engineering, including policymakers.

The issues of lack of experience and cost are somewhat intertwined as data has shown a definitive correlation between the experience of a Phius project team and the incremental cost of the project. With the increased adoption of Phius and passive building in various energy codes and incentive programs throughout the country, more and more developers are choosing to pursue Phius certification, thus increasing the demand for Phius Certified professionals.

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Why is Phius a cost-effective solution for developers?

Rader: The vast majority of Phius multifamily projects are affordable housing. In a growing number of states, the criteria for the low-income housing tax credit strongly incentivizes Phius Certification, making it a sound financial decision by the developer.

What role does building automation play in achieving Phius certification?

Rader: Phius sets energy conservation goals and project teams can reach them any way they want, which can and often does include automation features.

Prefabricated panelization is a growing trend in the high-performance building industry. As part of Phius’ product certification program, we certify prefabricated panels. (Editor’s note: Panel systems encompass full construction systems or partial systems such as a wall, roof or foundation. The program verifies that the system is a low risk for moisture problems and addresses the four control functions of a building enclosure—water, air, water, vapor and thermal—as well as a minimum level of critter control, such as insects and rodents.)

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How can indoor air quality be optimized in passive buildings?

Rader: One of the five core principles of passive building design is the use of balanced, mechanical ventilation—equal amounts in/out—and energy recovery ventilation. With the constant cycling of stale air from rooms such as bathrooms and kitchens out and fresh outdoor air in, passive buildings provide superb indoor air quality. 

How does Phius address the balance between energy efficiency and occupant comfort?

Rader: Energy efficiency does not require any sort of sacrifice to occupant comfort in Phius passive buildings. In fact, passive buildings are lauded for their exceptional comfort. The passive building design aspects such as the airtight building envelope, high-quality windows and strategic shading combine to offer consistent temperatures, no drafts, no cold spots, a quiet indoor environment and more.

Which property types are more inclined to achieve Phius certification?

Rader: All building typologies can be Phius Certified. We have certified schools, offices, single-family homes and even large-scale high-rises. For this reason, the term passive house is a bit of a misnomer, which is why we prefer the term passive building. 

To what extent is climate change impacting passive building?

Rader: Phius passive building projects are designed to mitigate and adapt to the climate crisis. The mitigation comes in the form of energy efficiency, the use of electrical mechanical systems and renewable energy etc. Phius buildings use between 40 to 60 percent less energy than regular buildings, which significantly reduces their carbon footprint.

In addition, the Phius standard is climate-based, so it is designed to meet the unique needs of various climates. This results in more resilient buildings that are equipped to handle climate-related weather events such as grid outages, cold snaps, wildfire smoke and more.

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What innovations or breakthroughs were discussed at the summit in terms of passive house design and construction?

Rader: Discussion at the summit focused on policy-related breakthroughs such as the Massachusetts opt-in Stretch Code that requires passive building certification for multifamily projects above 12,000 square feet and has been adopted by more than 20 municipalities, including Boston. Advancements in the Chicago Sustainability Policy, which heavily incentivizes Phius Certification, were also touched on. Industry leaders who played key roles in these advancements shared their experiences in communicating the importance of implementing passive building certifications into policy and effective strategies for affecting change.

Were there any discussions about integrating renewable energy sources into passive house designs?

Rader: The summit highlighted the cutting-edge work Phius does as a leader in energy-efficient building design. Renewable energy sources are an important aspect of the Phius ZERO standard. We are also researching microgrids and how they can work alongside high-performance passive buildings to create a more resilient grid.

Tell us about policy and regulatory aspects related to energy-efficient buildings discussed at the summit.

Rader: The policies discussed at the summit can be broken into three groups: incentives, Qualified Allocation Plans (QAPs) and energy codes.

Incentives help facilitate meeting the energy goals laid out by state agencies. Phius-related incentives are available in at least eight municipalities, including New York, Massachusetts and Illinois.

QAPs are documents that lay out the criteria for application to receive the low-income housing tax credit. The inclusion of Phius or ‘passive house’ generally creates a valuable incentive for affordable housing developers to pursue Phius certification. Twenty-one states include Phius, or passive house generally, as part of their QAPs.

Energy codes are the minimum energy requirements a building must achieve, while stretch codes push those energy stipulations further and alternative compliance paths offer options—such as Phius Certification—to meet stretch codes.