Last Updated: Oct 16, 2021
Rodrigo and Corinna Lema were tired of their Chicago home. The 1950s Georgian was drafty, which meant "money out the window," says Rodrigo Lema, a software designer. Adds Corinna Lema: "Our dream was to find a house less dependent on oil and gas," but the couple couldn't find anything they liked. Other homes had too high a heating bill and did not even come close to the couple's energy objectives. The couple decided, finally, to build their own home.
They found architect Tom Bassett-Dilley, of Tom Bassett-Dilley Architects in Oak Park, a certified Passive House consultant. "We didn't set out to build a Passive House," Lema says, "but we wanted more energy efficiency in our home than we'd experienced in a previous house or while house shopping. Tom convinced us to take the passive house route. He sold us on how insulation, solar gain, and balanced ventilation would allow the house to take care of itself."
The Lemas found an ideal lot in Chicago and began building their dream house. When completed in 2012, the Lema residence was the first certified Passive House in the Chicago area. Biltmore Insulated Concrete took care of the thermal shell. Evolutionary Home Builders served as the general contractor. Bassett-Dilley designed the home and conducted the calculations that would ensure high performance spatially, structurally, and mechanically.
Seven years later, says Bassett-Dilley, currently a council member of the Passive House Alliance, he's realized that "as building codes keep ratcheting up specifications for building tightness, and as we continue to translate the German Passivhaus standards to U.S. climates, the specifics of the locality are becoming more critical to the successful performance of passive houses in this country." That meant a few changes in the Lemas' home, as well.
Homes designed using Passive House principles have the most airtight and highly insulated building envelopes in the industry—resulting in heating and cooling loads way below those racked up by systems in a traditional home. Because of Chicago's climate of extremes—tropical heat and humidity in the summer, and polar vortices of bitter cold and aridity in the winter, the Lemas' home needed some cooling and heating.
The house has insulated concrete form (ICF) foundations and walls, a wood truss roof with plywood barrier and suspended ceiling, and Zola Thermo triple-pane aluminum-clad windows. With the structure in place, Bassett-Dilley could model the home's thermal performance and calculate how much heat and cooling the house would need
He selected a Mitsubishi Electric split ductless system. The system includes a condensing unit outside the home connected via refrigerant pipes to a non-ducted air handler inside. The system also has inverter-driven compressor technology. The two Mitsubishi Electric Hyper-Heating (H2i®) systems—one on the first level, another in the master bedroom on the second floor—were considered sufficient to condition the entire house.
The Hyper-Heating ductless system that Bassett-Dilley chose for the Lema house can operate efficiently and at full capacity even if the temperatures dip to 5-degrees Fahrenheit. The system can operate at 75 percent capacity when outdoor temperatures drop as low as -13 degrees Fahrenheit.
Over time, however, cool air in the summer wasn't reaching all areas of the upstairs. So the existing ventilation system was replaced with a conditioning ERV to balance out the air temperatures on the upper level, Bassett-Dilley explains.
"We're still considering a few things to improve the air mixing," says Rodrigo, including ceiling fans to help with air circulation." Still, according to Bassett-Dilley, "The systems monitoring and balancing the air in the house are effective. The air smells so good and clean."
Also, the Lemas discovered that in Chicago, as opposed to in Germany, the south- and east-facing windows on their home bring in too much solar gain in the spring before the overhangs that let in the winter warmth can block the angle of the April sun. The Lemas now install a special film on the windows during those months to help regulate the amount of sunshine and warmth that enter the home. They take the film off in the winter.
The Lemas' 3,800-square-foot home, which they share with their two children and two dogs, includes a finished basement used as a rumpus and recreation space for the family. It has an open-plan main level with living, dining, and kitchen areas, a den and in-law suite for Corinna's parents, a second floor with a master suite, two bedrooms, and a bathroom for the kids.
The Lemas' home also has a two-car garage with a 64-square-foot solar thermal array of collectors to heat the home's domestic hot water. The house is solar-ready for a future solar panel array on the main roof.
The Lemas took their Passive House to another level by becoming a pilot project for the Healthy Homes Initiative. All of the construction materials, finishes, paints, adhesives, and caulks used in the house are non-toxic. Cabinets have no-added-formaldehyde. The family used Greenguard Certification as a guide. The organization assists homeowners in identifying products for the interior of their homes that use materials with low chemical emissions.
"Building this house was an experiment for us," says Rodrigo, "so having a well-respected authority in the form of certifications proved we were doing things right." Bassett-Dilley brought in Brandon Weiss, LEED AP, and a Master Certified Green Builder and Passive House Institute U.S. Certified Builder to assist. Central Illinois Energistics, Inc. also conducted third-party testing and verification of systems and performance.
Rodrigo's advice for other homeowners considering Passive House construction includes making sure the crew building your house and installing the systems is up to the task. "We got lucky with the crew we used," he says. "They were extremely responsive and competent and quickly problem-solved when issues came up. It's important to find crew members who have had this work before."
He adds that he had to secure permits for many of the materials used in the house "because they hadn't been requested or used before, and weren't on the approved list." Moreover, when considering Passive House construction, consider where you live—and find an architect who can adapt Germany's standards to your climate and site. "In Chicago, we have sweltering summers and cold winters. The Passive House movement started in Germany, where the temperatures are milder." Adaptation is key to high performance and a cozy, comfy house.
"The best thing about the house is we don't have to worry about the mechanicals," says Rodrigo. "The mini-splits aren't even on a good part of the year, as we get so much solar gain through the windows, which keeps the house warm. When we have more than ten people in the house in the dead of winter, we have to crack open the windows—as those bodies heat the house fast."
Rodrigo adds that "Our house is in an area where some homeowners have two furnaces in the house! Their windows are leaky, the house is drafty, or they fear one furnace will go out, and their pipes will burst. We don't even have one furnace. People are so positive and curious about our home. I would do it again, but we built this house to age into. Having the temperature be so well controlled is a big plus for us."
Camille LeFevre is an architecture and design writer based in the Twin Cities.