Kat Klingenberg on Why Passive Building Has Finally Arrived

Kat Klingenberg designed and completed the first home to meet passive house standards in the U.S. in 2003. Two decades later, she's the founder of Phius, the nonprofit passive building institute in Chicago, watching the movement she helped build finally hit its stride.

She says interest is skyrocketing, costs are coming down, and the conversation has shifted from energy savings to something broader: health, comfort, and resilience. This is an edited and condensed conversation we had with Klingenberg from our Women at WIRC podcast. Listen to the full episode [here].

You finished your architecture degree and went straight toward passive building. What drew you there?

Klingenberg: The environment and the climate challenge were front and center in my mind. At the time, the cutting-edge projects here in Chicago that were in the magazines were two-by-six walls with fiberglass insulation. I did my undergraduate in Berlin, and passive house was already being talked about there, so I thought we could do better and that this was an opportunity. I decided I needed to build a prototype and show people how it can be done. 

That prototype was built in Champaign-Urbana, Ill. What surprised you in that process?

Klingenberg: I knew it would be difficult, but I’m also someone who likes experimenting. I like challenges. But the cool thing is that I found out that passive house had actually started there—the Germans got inspired by the first round of super insulation and high-performance buildings in North America, out of the Small Homes Council. So I wasn't alone, and the technology was already here.

That said, I made mistakes. I over-insulated, because I was thinking heating-dominated climate, but I was actually in a mixed climate. The Midwest climate is much hotter and colder than Germany, and there's cooling and dehumidification to deal with. At Phius, we eventually fixed that—we made the standard climate-adapted so it works everywhere.

What misconceptions do you still commonly hear?

Klingenberg: First, that passive building is only for houses. We're certifying a 53-story all-electric tower in Brooklyn, N.Y. "House" has become a complete misnomer, which is part of why we rebranded from the Passive House Institute to Phius.

Second, that an airtight building can't breathe. But you don’t want to breathe through stuff that is dirty; you want to be intentional about your ventilation and filtration. In old buildings, you're getting air through dirty cracks and crawl spaces. One of our HVAC instructors jokes about it this way: do you want to breathe through your underwear? With passive building, you're intentional—you bring air in where you want it, filter it at very high levels. COVID brought that front and center.

How has the conversation around passive building shifted?

Klingenberg: One of my technical associates recently noted that the benefits we used to market as secondary have become the primary benefits. People want safe buildings, great indoor air quality, comfort, resilience. The energy efficiency is almost icing on the cake now.

Give me a concrete example of resilience in action.

Klingenberg: During the snowpocalypse in Texas, a retrofit bungalow in Austin that was a certified passive house was the one where people could actually stay in when the grid went out. Even if it’s super cold, negative temperatures … the sun comes out, and you can sit in your living room and be completely comfortable without any heat. Same story in Houston during a heat dome, though it was the opposite end [of the temperature spectrum]. People were able to stay in the building despite the grid going down.

Pacific Northwest National Laboratory did a study comparing a code-built home to a PHIUS home and calculated how many more days the PHIUS home keeps occupants safe. So, there’s some significant data to back this up.

And there’s an urgency about this. The more we electrify, the more the grid gets strained. The biggest worry right now nationally is how do we scale up the grid with all the demand? The grid will go down. So, we need energy efficiency to stabilize the grid and to bring in that resilience factor.

But what about costs? Where do they stand?

Klingenberg: For larger multifamily, it's a real success story. Massachusetts incentivized eight passive multifamily buildings in exchange for detailed cost data, and those additional costs came back at just 2-3% on average. Developers said they couldn't afford not to do it. A New York City high-rise came in at 1.7% additional cost with a 12-year payback. Massachusetts has since made passive building standards code for buildings over 12,000 square feet. Single-family is still harder, but we're making progress.

For someone who wants to get started, what's the path?

Klingenberg: We have a Foundations training— online, and you get a Phius Associate designation if you pass the exam. It’s good grounding in building science without being overwhelming. From there, if you're a developer, hire a certified passive house consultant with real project experience. And come to our conferences; it’s a very open community, people share knowledge freely. Whether you’re a beginner or building science veteran, there's something for you.