How to build super energy-efficient houses

“The house won’t freeze if you lose power in the winter,” Kruse says, “which is a frequent occurrence in rural Maine.”

Katrin Klingenberg is executive director and co-founder of Passive House Institute US, a nonprofit that trains passive home builders and certifies buildings. She says that from 2011 to 2021, 16 million square feet of construction — single family homes, apartment complexes and commercial structures — was submitted for certification. The institute projects builders will seek approval of an additional 11 million square feet in 2022.

“We’re seeing exponential, hockey-stick growth,” Klingenberg says. “Any certified builder or designer with experience is in high demand and perfectly positioned in the market right now.”

Before construction begins, Kruse uses a software program to design a home and model its energy consumption based on a variety of factors, including the location of the building and the impact of insulation and airtight triple-pane windows and doors.

“It gets nerdy pretty quick,” says Kruse. “Rather than just building the building, you’re actually putting in a whole lot of information and then you’re evaluating how the house is going to perform before starting construction.”

The key indicator is air-tightness. In a passive home the slab, walls and roof are thickly insulated, and the shell is constructed to eliminate any pathways for air to escape. That requires a detailed plan to construct the home in a precise sequence so all the building materials fit together in a way that seals the structure. A ventilation system circulates fresh air, and the home is positioned on its site to maximize the heat it absorbs from the sun in the winter while staying cool in the summer.