By Jay Fox

When Second and Delaware first opened in December 2020, it was an anomaly. It wasn’t just because the two towers that make up the 330,000-ft², 276-unit development span an entire city block. It was because Second and Delaware was the largest Phius-certified development in the world and it was located in a part of the United States where few people had even heard of Passive House standards: Kansas City, Mo.

According to the architect on the project, Jeffrey White of Jeffrey M. White Architect D.P.C., he and developer Jonathan Arnold, CEO of Arnold Development Group, were instantly drawn to Passive House design upon hearing about it more than a decade ago. White credits Arnold with learning about it first, who then reported back to him. “He said, ‘This is a much better way to go about studying and understanding heat transfer; the physics of structures; and how can we make them more fireproof, more acoustically dense, and give them a longer lifespan.'”

Though market awareness of the Passive House standard was lacking and despite the fact that no one in the United States had built anything nearing the size of Second and Delaware, Arnold felt compelled to take on the herculean task. “There’s a moral obligation to take action and reduce energy consumption,” he says. “With Passive House, you can do that cost-effectively.”

Building Science as an Amenity

On top of building efficiently, Arnold envisioned creating something that lasts hundreds of years. As he sees it, this allows multiple generations to make use of the embodied carbon that has to go into the building in the first place. He also felt that the development needed extensive greenspaces, including both a courtyard and expansive gardens on the roof. Given the priority of durability, the size of the buildings, and the fact that they would need to support rooftop gardens that span 55,000 square feet across both rooftops, the team decided to use structural concrete all the way up to the roof for each of the six-story towers.

In addition to the rooftop gardens, the development almost feels like a campus due to the massive courtyard that is artfully landscaped and punctuated by fire pits and tables where residents can congregate. There’s even an outdoor pool. Amenities abound within the building, as well. There is a large fitness room and community spaces, which are all situated in the Passive House envelope. Location is another benefit, as Second and Delaware is within walking distance of the thriving City Market neighborhood. Residents can also easily hop on the bus or the KC Streetcar, which both have stops within a few blocks of Second and Delaware. For those who prefer to have a car, there is onsite parking below the buildings (and outside of the Passive House envelope).

However, the standout benefit of moving into Second and Delaware is its Passive House design. For Arnold, it represents a win for renters because it guarantees a space that is quiet, healthy, and comfortable. This is an important point that Arnold returns to repeatedly, and it is something that developers of Passive House projects and even architects who want to build to Passive House standards should keep in mind.

The marketing team at Second and Delaware is not selling carbon reduction. They are selling the fact that renters can walk around barefoot and still be comfortable. They are selling the fact that the building is across the Missouri River from a major railyard and international airport, and yet management does not receive noise complaints. According to Arnold, the building is so soundproof that neighbors can’t hear one another. As he relays, one renter was astonished to find that she’d been living next to a family with a newborn for months but had never ever heard the baby cry.

True, Passive House construction requires more upfront capital when compared to buildings that meet code minimums, but this does not make them more expensive per se. As Arnold told Green Building & Design (gb&d) in an article from 2021, Passive House buildings cost far less to heat and cool than conventional buildings, and owners and developers can capture those savings to increase net operating income by including utilities within the rent structure. “We incorporated a market-rate utility expense into the rent structure, which allows the owner to benefit from the energy savings and apply that toward paying for the increase in the quality of the building, namely, triple-glazed windows and durable construction,” he said.

“That’s how we  change the industry,” Arnold told Passive House Accelerator. “We can show that it doesn’t cost you anything and you have a better yield and that isn't even factoring into the equation that we do have higher rents, because people enjoy living in a building that's warm and quiet and well-built.”

Arnold’s gamble paid off. Despite opening during one of the bleakest periods of the pandemic, all 276 units were occupied within seven and a half months. It was one third of the time they thought it’d take to lease up the building, according to Arnold. Moreover, occupancy rates have remained extremely high because renters really enjoy the benefits of living in a Passive House and the word has spread.

“The market notices the difference,” Arnold says.

Lessons Learned

Of course, it hasn’t all been easy. There had never been a Phius-certified building constructed at this scale anywhere in the world, and working on such a trailblazing project required working through details that did not have readily available solutions. To understand some of the lessons the team learned along the way, we reached out to engineer Galen Staengl (Principal at Staengl Engineering), developer Jonathan Arnold, and architect Jeffrey White to see what future teams should know.

As a significant example, the team wanted to create a replicable template for their structural elements, which led them to explore the idea of using aluminum forms to set the cast-in-place concrete floor plates and walls. Unfortunately, using these forms when trying to create an exterior wall system of concrete and rigid insulation did not work as well as they would have hoped. The idea of using forms was ultimately abandoned, but the team kept the design of the wall assembly, which Staengl refers to as a concrete and rigid foam sandwich (see Figure 1).

Similarly, gas was still the norm for domestic hot water systems (DHW) in multifamily buildings at the time, especially within the U.S. Even in Passive House projects that have been completed within the last two or three years, installing all-electric systems within large-scale residential buildings has not been a given, though this is thankfully changing.

One last preliminary note: As sourcing occurred at a time when high-performance building markets in North America were far less mature than they are today, many of the components that initially went into the building had to be shipped from Europe. There simply were no alternatives in North America at the time. Again, this is thankfully changing.

Despite the challenges of building to Passive House standards, White and Arnold say they were able to build an incredibly effective team of consultants early on who understood the physics of Passive House, and that this ultimately set them up for success. At the top of the list of consults is Galen Staengl, who White describes as their “MEP guru.”

“I can’t say enough good things about Galen’s capabilities and the ways he’s worked with us,” White says.

One of the most obvious benefits of using a local manufacturer is that it reduces logistical difficulties. Getting a component from the factory or warehouse to the job site is always complicated and more expensive than teams want it to be. It only gets more complicated and expensive as the distance components have to travel increases and the size of the project gets bigger. (White also notes that getting a metric-based factory to try to integrate with a U.S.-based project adds a layer complexity that is best avoided.)

For example, approximately 30% of the façade of Second and Delaware is glazing, according to Arnold. As anyone who has worked with a triple-pane window knows, these units are not just bulky; they are also very heavy. There is no world in which it is cheap to ship that many windows across the Atlantic. Unfortunately, they could not find a local supplier capable of delivering an order of high-performance windows that large, so they had to import all 750 units from Europe.

Using a local manufacturer or an international firm with a regional office nearby is also beneficial because local contractors can work a lot easier with a firm that is based nearby as opposed to one that is based solely overseas. Working with firms that are established in the region also means that building managers can contract out maintenance work to a wider network of firms because there is greater familiarity with the components. Consequently, Staengl advises looking for a good and local network capable of supporting and servicing the equipment before you commit to using any major building system.

Looking forward, Arnold says that ease in maintenance is one reason he has become interested in using geothermal systems. As he explains, there are more contractors capable of working on geothermal systems because they are relatively straightforward and rely on easily sourced components. He’s also exploring their use because they do not rely on refrigerants, which are subject to a shifting regulatory environment.

Though this was not discussed with any member of the team at Second and Delaware, it should be noted that going local can reduce the effects of sudden and capricious tariffs. Though it is not necessarily going to fully insulate project teams from the effects of tariffs, as many local manufacturers rely on international supply chains for components or tools that are used in their day-to-day operations, it can mitigate price shocks associated with said tariffs.

Use Mockups

Preventing air leakage is important in any Passive House project and Second and Delaware is no exception. As White explains, the team worked with great companies in the area, built mockups, and ensured that they had good connections at the windows and doors. “It’s not easy trying to create methodologies that bridge the connections between windows and walls, all while trying to meet the Passive House requirements,” White says. “We did full size mockups and took it to the wind tunnel and cranked up the wind speed to 190 mph to see if it would leak,” he adds.

These efforts paid off when they did their final blower door test. “We knocked it out of the park!” Staengl beams when noting their airtightness scores of 0.032 and 0.09 CMF50 in the east and west towers, respectively.

Model Disparities

One of the more perplexing issues that Staengl has come across is that electricity use in the building has been around 10% higher than predicted.

One clear factor affecting energy use is that residents are in their units for more hours per day than anticipated, as modeling was conducted prior to the COVID-19 pandemic. Even though many workers have returned to the office and their day-to-day patterns with respect to work are more aligned with pre-pandemic times, studies suggest that leisure time is not as social as it once was. As one 2024 study by researchers from UCLA and Clemson University found, individuals have spent an average of 51 fewer minutes per day doing out-of-home activities on average when 2021, 2022, and 2023 figures are compared to 2019 figures. People of all ages are simply more comfortable being homebodies, which inevitably leads to more energy use in the home.

Final Pieces of Advice

One of the most commonly repeated pieces of advice for projects teams is to bring on as many core members of the team as early as possible. In a Passive House project, this includes the MEP engineer. White notes that this position is absolutely vital because they create the mechanical structures that undergird the design. Having someone who is experienced, enthusiastic, and deeply invested in understanding the physics of buildings will never allow the design team’s vision to ignore energy efficiency or functionality. White also advises hiring this engineer as a full-time consultant because they need to be answering detailing questions constantly, especially during preconstruction.

For construction scheduling, Staengl says that working in multiple early blower door tests helps to ensure that everything is working as it should and nothing is being overlooked. “It’s not a checklist like LEED,” he says. “Everybody needs to be made aware, repeatedly, of what needs to be done in order to be successful.”

For future developers and owners of large-scale Passive House buildings, Arnold would caution against exploring too many novel technologies at once. While he is personally excited about building-integrated photovoltaic technologies and some elements of prefab, he also recognizes that untested technologies can add risk and potentially costs to projects and that it’s important to find the kind of balance between innovation and convention that made Second and Delaware such a success.

While there were a lot of innovative technologies and design elements involved in the construction of Second and Delaware, they were solidly grounded in building science and passive principles. And though there were a lot of challenges and growing pains because the team was ahead of the market, when asked what he would have done differently, Arnold chuckled.

“I would just build the same building again.”