Our intention: turn an average old house, on a standard urban lot in a very cold city, into an affordable place to live, combining net-zero energy consumption with creature comforts and the ability to “age in place.”
Our daughter found this house in Minneapolis, where Linda and I intended to move after retirement; it was in foreclosure, had basement water damage, and had an unfortunate rear addition with a mismatched roof pitch. It was in need of renovation. Linda was, at first, not so sure about “net zero.” She assumed that both aesthetics and comfort would be compromised in the quest for super-efficiency. Nor was I sure that, once the numbers were crunched, reaching net zero in an old house on a small city lot would be feasible, or affordably so. So we hired Marc Sloot of SALA Architects, who has experience in green building. “It wasn’t just about reaching energy goals,” Sloot says. “It was also about preserving a 1907 house and keeping the character of the neighborhood.” Sean Morrissey (Morrissey Builders, St. Paul), also with considerable experience in sustainable construction, was hired as general contractor.
After a 15-month renovation, the result was an all-electric house that surpassed net zero—producing 17,000 solar kW hours but using only 12,000. It has 54 solar panels, four 25-foot-deep geothermal wells, and super-insulation. The house is heated with the wattage equivalent of a blow dryer.
We sell the surplus energy to our utility. In the first year, the system produced about $3,000 worth of electricity, yielding a return of about 7% on the initial investment of $40,000 (after the federal tax credit). And we have the satisfaction of knowing that we rescued and improved a sound, 111-year-old house.
Because of housing density and existing trees, “passive solar was out of the picture here,” our architect explains. “To get to net zero, we had to reduce energy consumption drastically, relying on the performance of the structure and systems. “In addition, solar exposure on the main roof and the garage roof would allow for installation of photovoltaic panels to produce electricity.”
From the street, the house looks like a Victorian cottage, albeit brand new. A passerby isn’t aware of new energy technologies. Inside, the house is filled with original woodwork that was saved and reused, while new millwork in sustainable lumber was faithfully copied. (The previous rear addition had been poorly constructed and had no detail.) Structural problems—including the broken roof line and floor levels that didn’t match—were addressed. The much-improved interior now has a bright kitchen, an owners’ suite, two offices, and a sunroom.
Retrofitting always has its challenges, but solutions are multiplying. For example, take the foundation insulation, which a tight house needs. Insulating on the inside isn’t very effective. The house is on a narrow lot with little distance from the neighbors, so using a backhoe to excavate would be impossible. Our crew used the “cocoon method,” hydro-vacuuming a five-inch trench next to the foundation, then inserted a two-inch foam sheet and sprayed expanded polystyrene (EPS) insulation. Without removing much dirt, the effect is R-30.
The old roof on the balloon-framed house was undersized, so we built a new roof of plywood I-beams over it. The spaces between are filled with 10 inches of foam, insulating the roof to R-80. It supports 42 solar collectors, thanks to a laminated beam running the length of the attic, which workers installed by hand (as six 300-lb. pieces) rather than by crane. The beam rests on steel posts that invisibly run through walls to foundations in the basement. Where there’s a will there’s a way.
Our house has been certified LEED Platinum as well as net-zero by the International Living Future Institute. When I reviewed the lists in the journals, it became clear that ours is the only 100+-year-old house to receive both certifications.
BETTER THAN NET-ZERO VICTORIAN
• ‘PERSIST’ system wall insulation to R-40
• Foundation insulation effectively R-30 with cocoon-method foam sheet and spray foam
• New roofing system insulated to R-80 and supporting 42 solar collectors; an additional 12 collectors are on the garage
• Captured heat: exhaust from baths and kitchen warms incoming outside air through an enthalpy recovery ventilator (ERV); excess heat from geothermal heat exchanger pre-heats water; water heater heat pump captures heat from basement air
• Triple-glazed windows cut down on heat transfer in all seasons
• Result year one is net-positive: electricity consumption 12,000 kW hours with 17,000 kW hours generated by solar panels
• Constant temperature with no need for nightly setbacks at thermostat
• Continual fresh air, conditioned through a heat exchanger: no need to open windows
• Gentle forced-air heat, auto-regulated to a comfortable humidity
• No drafts or cold spots, thanks to super-insulation and an envelope that meets the passive-house standard for infiltration
• No combustion in the house, reducing dust to a minimum (we dust once a month, if that)
• A four-season sunroom owing to triple-glazed windows
• Little to no condensation on window glass, thanks to a 60% outside/40% inside insulation split at the vapor barrier
• Absorption of formaldehyde into specialty wallboard, rendering it inert
• Hot water arrives at any faucet within five seconds, thanks to a recirculation loop
• A never-depleted supply of hot water from a heat pump-driven water heater
• Basement temperature of 64° without supplemental heating, due to cocoon method of insulating the basement exterior to R-30 (without disturbing flowerbeds)
• Triple glazing substantially reduces outside noise
AGING IN PLACE NET-ZERO VICTORIAN
• Freedom from rising energy bills
• Rear entryway can accommodate a future ramp
• Lever door handles on exterior doors make entry easier
• Interior doorways wheelchair-wide
• Staircase can accommodate a stair elevator
• Grab bars in shower and tubs, along with easy-to-clean wall-mounted toilets
• Soft-close pullouts and drawers in cabinets
• Washer and dryer comfortably raised 12" above floor and served by a laundry chute
• Bright LED lighting throughout, including in closets, and sensor lighting outside