First Passive House in Chicago Gets a Few Revisions

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.

Passive House Principles

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.

A Passive House, Revised

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.

Healthy Home 

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.