Jul

01 An Energy-Efficient Tudor Retrofit

This Tudor house in Geneva, Illinois, went from downtrodden to desirable, thanks to an energy-efficient retrofit that was mindful of the house’s history.

Ernie Mahaffey is not a house flipper. He bought the vacant house up the block from his own home of 20 years in Geneva, Illinois, because he “could see the vultures swooping in.” The under-loved 1929 brick Tudor with a rampantly overgrown landscape—newly vacant in the height of the housing boom—provoked in him a familiar desire: to rehabilitate a fixer-upper threatened with destruction.

The place was a wreck, according to a seven-item summary of “major structural defects” Ernie’s building engineer cataloged. Unfazed by the prognosis, Ernie decided he would go beyond the structural repairs to upgrade the house to the strictest efficiency standards in the world: the Passivhaus.

Developed in Germany, Passivhaus standards call for an extreme reduction in a building’s carbon footprint. Through stringent requirements on insulation, infiltration, and heat retention, the standards result in a building that needs almost no input from an HVAC system to regulate indoor climate. Hitting these standards—or even coming close—would have major implications. The home could act as a case study to show how radical new building techniques could preserve existing structures while cutting their consumption to near zero. Ernie envisioned a historic homeowner’s dream: a subtle blend of state-of-the-art new systems in a building that retained all the charm and character of decades past. To pull it off, his architect, Tom Bassett-Dilley of the Oak Park, Illinois, firm Drawing On Place, would use the house as a laboratory to challenge the conventional wisdom of restoration.

Energy Matters

The time-worn front door, a distinctive detail, was completely rehabilitated.

Under the close scrutiny of the Geneva Historic Preservation Board, Tom knew that adding conspicuous new materials to the exterior of the house was out of the question. But his desire to bring the house to cutting-edge 21st-century standards didn’t exactly provoke a clash with the board.

“Historic preservation is energy efficient,” says Karla Kaulfuss, Geneva’s historic preservation planner. “And true energy efficiency is about looking at the whole project, then evaluating each building for its own issues and its own capabilities.” Preservation is a balancing act, she says, requiring an open-minded approach from both the board and the owners to achieve what is ultimately a shared objective.

For instance, the house gains much of its character from a stunning series of divided-light windows, an oriel on the front façade, and a 12-tall picture window in the vaulted-ceiling great room. The Preservation Board insisted the original windows stay, so Tom upped their efficiency by rehabilitating the original sash. Then he finessed a cost-effective standby: Original wood storms were reglazed with single-pane glass with a low-E coating. For the few storms too worn to recondition, the team made new storms to match out of white pine. For maximum seal, storm windows also were installed with peel-away caulking along their interior edges. “It’s just good building science,” says Tom. “It’s about how you take care of the envelope, and you can do that for not a lot of money.”

Two varieties of high-tech insulation were installed in the house—white open-cell foam in attic rafters and dense-pack gray cellulose on the walls.

A solid building envelope—basically, an unbroken exterior barrier that maintains a static indoor temperature—is central to the Passivhaus philosophy and to Tom’s plan. “The house had zero insulation,” says Tad Hemming of Hemming Construction, the project’s general contractor. Tad and Tom mapped out a strategy that would eliminate every “thermal bridge”—a spot that allows heat to pass through the house walls.

The team added dense-packed cellulose to every wall stud bay and installed 7 of air-impermeable open-cell foam in attic rafters. Because heat migrates through the studs on exterior walls, Tad ran ½ furring strips perpendicular to the studs on their interior face, allowing an extra layer of insulation to envelop the framing members so they don’t make direct contact with the finished wall surfaces.

“They just insulated like crazy,” says Tony Botkin, an energy auditor from Intelligent Energy Solutions, a nearby firm hired to measure the house’s efficiency. Tony describes the dense-pack cellulose technique as a cascade of fibrous wood pulp passing through a stream of water before entering the stud bays. “It’s almost like blowing a spitball into the wall,” he says. “You just fill it until you can’t fit any more.” As Tom puts it: “We took a house that was really leaky and drafty, then with good insulation, good storm windows, efficient lighting, and the right-sized furnaces, built a house that’s way better than the current energy code—and this is for 1929 construction.”

Maintaining History

With the big-picture energy issues solved, Tom could focus on the historic details essential to the restoration. To rebuild a collapsing exterior wall, Steve Patzer, a talented local mason, hand-numbered individual bricks as he took them down so he could reassemble them in exactly the same position using a skintled brick technique. Tad’s crew re-created knockdown plaster walls in the front parlor rooms by spraying drywall mud through a wide-broadcast nozzle, then using 2 knives to smooth the resulting cake-icing stipple into a coarse surface.

Before work began, the kitchen was in such bad shape that no appliances remained. The finished room retains an arched entryway and radius window, while adding new cabinets and countertops.

In the front parlor, Tad removed the exposed beams from the vaulted ceiling to insulate and wire the framing above the large, airy public space. After cleaning and re-staining the beams, Tad says, “I shot ‘em with polyurethane and hung ‘em back up.” Ashes were flowing from the room’s massive fireplace when the job began, so Tad rebuilt the firebox flue line and replaced its broken damper with a stainless steel door. A cast-iron Juliet balcony rail, overlooking this room from the upstairs hallway, was one of the few details that required no restoration.

The living room’s rustic ceiling beams were carefully removed and reinstalled.

With the Preservation Board’s approval, the crew also created a rear addition with a master suite, upstairs laundry, and spa shower. Tad built the addition to the highest energy specifications, but he says the retrofit on the historic section proved to be no more of a construction challenge than building from scratch. “If you have the opportunity to open up the walls, you can do pretty darn well,” Tom says. (Because the home’s original interior was in such bad shape, the walls had to be rebuilt anyway.) Although he was referring to the effort to improve efficiency, Tom was equally successful in the pains he took to maintain historic elements.

“The house is a hands-on example,” says Liz Safanda, chair of the local Preservation Partners of the Fox Valley. “You can lecture in the abstract, but this is a case study—windows, masonry, public façades, and a compatible addition. To have something visible and tangible, it really adds to the theoretical discussions.”

The data from Tony Botkin’s efficiency tests show that the house’s consumption is nearly 70 percent below its pre-renovation levels. Factor that in to the resources and energy already embodied in an existing structure, and it’s easy to see why Tom suggests that an efficient retrofit—rather than airtight new construction—is the more sustainable choice. “You don’t have to get rid of a piece of history and all the culture that comes along with it,” he says. “You don’t have to lose your home.”