A Net-Zero Historic Retrofit

A Net-Zero Historic Retrofit

A motivated homeowner revamps his historic home for net-zero energy and net-positive water.

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Grocoff and BLUElab graphic

Green Builder Media

Wednesday, August 5, 2015 - 7:00am

CAMPAIGN: Ethical and Sustainable Living

CONTENT: Article

BEFORE HE MADE his energy bills disappear, Matt Grocoff was paying $350 a month for heating in his historical, 2,600-square-foot home in Ann Arbor, Michigan. If all goes as planned—under the strict objectives of the Living Building Challenge that Grocoff is aiming for—his water bills may also soon disappear.

Grocoff, an environmentalist and founder of the THRIVE Collaborative, has always emphasized the importance of designing a net-zero-energy system, not just a net-zero-energy building. While it may be easy to blame the home’s occupants for lacking eco-friendly behavior, Grocoff believes that behavior change in the home is a difficult thing.

“Changing a shower head to higher efficiency will do more to save hot water than by telling someone to turn off water while shaving. We should still tell people to conserve water, but we should also put energy into systems, and not just focus on behavior changes. I can knock off several more kilowatts just by buying a $1,500 appliance—I don’t need to spend $10,000 insulating my basement. It’s a great point that people are missing in net-zero building,” Grocoff points out.

In fact, plenty of people told Grocoff that net-zero energy wouldn’t be achievable in such an old home, unless he installed triple-pane windows and a slew of other pricey features. But Grocoff and his team were able to keep the original single-pane windows by restoring and weather-stripping them and then adding storm windows.

Naturally, part of the net-zero strategy was adding insulation, including blown-in cellulose in the walls and spray foam in the attic.

The original stone walls of the basement, however, allow for energy loss during the winter—but in the summer, that same feature works as part of a mechanically assisted natural ventilation system, which was part of the house’s original design. Warm air flows in through the windows of the basement, drawn in by an attic fan, and is cooled there. The main floor windows remain closed, and the attic windows are opened to release the hot air. The flip of a switch determines if the natural ventilation or the AC will cool the house, depending on the outdoor temperature and humidity levels.

“It’s about making simple rules for local interactions, just the way nature does. And most people will choose natural ventilation most of the time,” Grocoff says.