Yannell PHIUS+ House

In 2050, the year the United States hopes to achieve a net-zero emissions, an estimated two-thirds of today’s commercial buildings will still exist. With a predicted median age of 70 years old, those structures may hinder our progress toward a carbon-free future. April Hughes, AIA, owner and managing principal of the Chicago firm HPZS, is well aware of this reality. “We have to figure out how to retrofit our existing buildings in order to make these goals,” Hughes says. “You're not going to meet 2050 decarbonization goals if you don't touch existing buildings.”

In 2017, Hughes realized she had a chance to make a statement when Michael Yannell, a local developer and previous client, came to her with a proposal to renovate a vacant, 130-year-old farmhouse in the Ravenswood neighborhood of Chicago. The resulting Yannell PHIUS+ House is the first single-family passive house renovation in the Midwest, serving as a case study for the importance and potential of retrofitting historic structures. The project began with a simple question: What is a passive house? “We barely know ourselves,” Hughes recalls saying. “We’re going to figure it out.”

The firm did its research, determining that a straightforward retrofit of the existing structure was unlikely to generate a profit—the cost of the property and the renovation itself would exceed the realistic market value. “The next step was, what would happen if we increased the square footage?” says Hughes. “Could we … still meet our passive house requirements, and actually be able to sell this at a profit?

The firm designed a 500-square-foot addition, resulting in a 4,027-square-foot, five-bedroom, three-bathroom house with a higher market value. But that was just the start. “We knew that we were going to run into several issues right away,” says HPZS junior associate and project manager Caryssa Buchholz, Assoc. AIA. Passive house standards require a continuous insulative barrier—a challenge given the house’s existing brick foundation. In the basement, HPZS brought the insulation inside the house instead of excavating around it.

The house’s original balloon-framing, however, was easier to navigate. “The old traditional methods of balloon-framing allowed us to insulate the entire height of the building more easily than it would have been had we torn it down and built new,” Buchholz says, as the house’s studs went from the first floor straight up to its roof. “This is another push for using existing buildings.”

For the project, HPZS used a variety of insulation types: R-48 graphite-infused continuous insulation on the exterior, a closed-cell polyurethane wall insulation on the interior, and 3 feet of R-100 blown-in glass mineral wool insulation for the attic.

Permitting proved another challenge: the project was on hold for six months as city officials decided whether the passive house insulation counted as new walls, which would have necessitated additional permitting. “It was just very basic situation that most older buildings in Chicago will probably run into,” Hughes says. “The city is going to have to change its zoning policies to allow this type of development—sustainable, energy-efficient development—to occur.”

Construction began in 2018, with HPZS sourcing low-VOC materials and weaving sustainable systems throughout the project. An energy recovery ventilator that provides clean outdoor air and a zoned variant refrigerant-flow HVAC system minimize the house’s energy demands, which are further offset by an array of solar panels that provide 25% of the house’s annual energy needs.

Inside, the Yannell House’s open-plan layout and triple-pane, argon-filled windows create a bright space that increases the project’s lighting power density. Outside, the house’s grey and white, Hardie board exterior gives a modern twist to a traditional form—serving as a kind of “pivot,” as Hughes says: “Existing homes still have a place in a carbon-free future.”

The project hit the market in fall 2019, selling right after its first showing. But HPZS is looking ahead. “What’s the next demonstration?” Hughes asks. “Now that we've proven from the building science perspective that you can do a retrofit like this in Chicago, how can others do this of their own volition? More importantly, how can we figure out how to get zoning code and building code to the point where this is just something we do because it raises the baseline for everyone?”

Project Credits
Project: Yannell PHIUS+ House, Chicago
Client/Owner: Michael Yannell
Architect: HPZS, Chicago. April Hughes (owner/managing principal), Caryssa Buchholz (project Architect/project manager), Sheila Schaefer (interior designer)
Interior Designer: HPZS
Mechanical Engineer: dbHMS
Structural Engineer: Goodfriend Magruder Structure LLC
Electrical Engineer: dbHMS
Construction Manager: Marek Bajkowski
General Contractor: MK Construction
Air Sealing/Insulating: Windy City Air Sealing
Size in Square Feet: 4,027 square feet
Cost: $1.5 million

Materials and Products
Appliances: Bosch
Bathroom Fixtures: Studio 41 provided Kohler/Grohe
Carpet: Mohawk
Cabinets: Exclusive Design Center
Countertops: MSI
Exterior Wall Systems: Hardie
Flooring: White Oak Wood Flooring/Daltile/Anatolia/MSI
HVAC: York
Insulation: Thermoseal/Knauf/ThermalStar
Kitchen fixtures: Studio 41 - Delta
Lighting: Kichler/Progress
Paints and Finishes: Sherwin Williams ProMar 200 Zero VOC/ECOS Floor Stain
Photovoltaics or other Renewables: Solaria
Windows and Doors: Sierra Pacific/Thermatru