A Minnesota couple has almost, but not quite, built the net-zero energy house 25 miles from the Canadian border. A story by David Shaffer in the tomorrow's Star Tribune business section points to the article the couple published in the September/October issue of Solar Today.
Architect Nancy Schultz and husband Dr. John Eckfeldt , a professor at the University of Minnesota Medical School, built their lakefront home near Isabella, Minn., 80 miles northeast of Duluth.. It's is tightly insulated with R-values of 55 and 90 in the walls and roof.
It has passive solar heating using south-facing glass, plus a rooftop solar heat collector that recirculates liquid through an experimental heat-storage “crib” beneath the house filled with sand, gravel and taconite ore pellets. The house also has a heat-recovery system for outgoing air and a ground-loop system to preheat incoming air.
Other rooftop solar panels generate electricity. A small electric boiler is a backup heat source. Overall the house is “near net-zero,” meaning is uses almost all renewable energy and has almost no carbon footprint.
“We have been going up there for 30 years,” said Schultz. “We decided to build it as an experiment station.”
But Minnesota winters were still too much. In the article, the couple said the heat-storage system wasn’t able to keep the house at 70 degrees F when the outside temperature was minus 40 degrees, but they are working on improvements.
But it's not cheap. The house cost $342 per square foot, compared to $200 per square foot and up for a conventional house, Schultz said.