South Harpswell sits at the end of a narrow peninsula, facing due southwest toward Casco Bay. Like a lot of coastal hamlets in Maine’s mid-coast and Downeast regions, the land formations are long and irregular, resembling flecks of paint being thrown onto a canvas from a distance. In other words, the topography is unique.

In the early 2010s, architect George Penniman sought to build a modest cabin on a plot of undeveloped land fronting Ash Point Cove, near the terminus where the mainland’s jagged fingers give way to the sound. But unlike the countless other weekenders seeking that rustic log cabin feel at the water’s edge (Penniman lives and works in Connecticut), Penniman wanted his home away from home to have minimal environmental impact. He wanted a passive house.

“We wanted to leave as light a footprint as possible on the land,” Penniman says. He and his wife Anne, a landscape architect, used locally sourced lumber, stone, and other materials to build and finish the home. Most notably, they installed helical piles for the foundation.

“We didn’t want a basement, we didn’t want all that concrete, and we didn’t want to risk damaging the roots of the trees,” Penniman says. They likewise wanted to avoid the use of foam insulation, fossil fuels for heating, and bringing large construction equipment onto the densely forested pocket of land.

Through this process of elimination, coupled with Penniman getting certified in passive house design, their vision was coming into focus.

Helical piles for a low-impact build

The idea of building a passive house first crossed Penniman’s mind in 2012 after he saw a presentation by Chris Corson, owner of Maine-based Ecocor, a design-build company specializing in low-carbon, net-zero-ready homes. Corson was an early adopter and builder of passive…