Dubbed “Passive House in the Woods,” this project takes energy efficiency far beyond the experience of most residential builders. It’s a bleeding edge design, a strikingly modern structure that produces 65 percent more electricity than it needs. It also has an interesting back story.
“The client’s wife was ill with cancer as we were planning this home,” notes architect Tim Delhey Eian. “She passed away before construction began, and we ended up changing the design to a much more vertical plan.
“We chose ICFs deliberately, as a pretty failsafe construction method,” he adds. “I had a good grasp of Passivhaus concepts, because I grew up in Germany and completed the training there.
Although the systems in this home are familiar, this project takes them to a higher level. The ICFs, for example, extend below grade, and are augmented with an EIFS system that includes 11” of EPS foam above grade—making a wall 22” thick with an R-value of 70. Many parts of that EIFS system had to be imported from Germany.
“We tried to get the North American branch to provide the system, but the deal fell through,” the architect notes. “They only offered the system in Europe. It puts all of the water management on the exterior. I think since then they’ve started offering it in the U.S.”
The flat roof includes 14” of polyisocyanurate foam, achieving R-95, and the windows and doors, imported from Germany, are triple-pane, low-E coated, with insulated frames. They have an installed R-value of 8. By comparison, a typical wood or vinyl framed, dual-pane, low-E window achieves only about R-2.
The slab also sits on 12” of EPS foam (R-60), and the garage doors are insulated as well, so the overall heating demand for the home is extremely low. In fact it has no furnace and no fireplace, despite the cold climate. The home, designed for a heating load of just 3,000 watts, relies entirely on passive solar, a modest ground loop geothermal system and a back up electrical system of heating. A super-efficient HRV provides ventilation to the whole house, with minimal loss of BTU.
Along with the 4.5 kW PV panels, the house has a 40 sq. ft. hot water solar collector that provides 90 percent of the home’s hot water demand. A small electric hot water heater provides the rest.
The architect notes that by monitoring the home’s performance during the first year, the team was able to identify hidden energy wasters. “For instance,” he says, “We no know that the well pump was using a lot of energy—12 percent of the home’s consumption for a year. That was easy to improve.
“At the same time,” he adds, “some of the appliances out-performed our original estimates, in part because they weren’t used as much as expected. But we’re now extrapolating from the lifestyle impacts.”
Too often, notes the architect, home owners look at the aspects of a home that are not important—things that “are really going to go down the drain.” Not so, with this house, he says. It’s a project that ultimately gives the resident freedom—so they don’t owe monthly bills to anyone.
