When architect Terrell Wong and her husband decided to conduct an energy-efficient renovation of their 90-year-old home, there were many parts of the house they wanted to preserve. The house, which had been in her husband’s family for 35 years, had beautiful hardwood flooring and dark kitchen cabinets that her mother-in-law had commissioned 35 years ago. Plus, it was located in the historic Rosedale neighborhood of Toronto.
“I wanted to honor it,” says Wong, owner of Stone’s Throw Design in Toronto. But there was one important feature of the house Wong wanted to do away with: the $12,000 annual utility bills. The home’s heat was provided by two gigantic oil tanks in the basement. The construction was typical of a home from its time period: The exterior was 8-inch brick, with a lathe and plaster interior—and no insulation.
“The goal was to add efficiency while preserving as much of family significance as possible,” Wong says.
Her solution looks to both the past and the future. Wong kept some features, like the exterior façade, flooring, stairs, and a few treasures the family found while preparing for the retrofit, but they completely overhauled the home’s energy usage.
Wong used techniques from the Passive House method, a holistic energy-modeling concept pioneered in Germany. She spent $50,000 on insulation, upgraded windows, and a ventilation system. The investment paid off: She lowered her utility bills by $10,000 per year and cut energy use to less than 50 kWh per square meter (equivalent to a HERS rating in the low 40s in the United States).
The transformation started in the building envelope, which had leaked air at a sieve-like 11 air changes per hour. To maximize air tightness and space for insulation, Wong issued a challenge to her contractors: nothing but insulation in the walls. The exterior wall would be virtually sacrosanct, with no pipes, vents, ducts, wires, or outlets in the walls unless absolutely necessary. Floor plugs turned out to be a key tool in meeting this challenge. They replaced all required outlets on the exterior walls and had the added benefit of providing a clean look—though at $60 each, they had to be used sparingly.
With the historic façade set in place, Wong had to work inward to add insulation to the house. From the foundation to the underside of the eaves, she kept the original 8-inch brick and filled a 2-inch air space behind it with spray foam to prevent thermal bridging. Behind that, the new, non-structural interior walls are made from 2x4 wood studs, 24 inches on center, with steel studs on the top and bottom. The space is filled with more spray foam for a total of 5.5 inches of insulation and a total wall R-value of 35. The roof, meanwhile, is insulated with 2 inches of spray foam topped with cellulose for an R-88.
Wong also replaced 10 windows in the back of the house with triple-glazed, R-7 German-made Internorm Varion windows. While the added insulation meant she lost 4 inches of living area along each exterior wall, the energy change was dramatic. With the spray foam acting as a vapor and air barrier, leakage dropped from 11 air changes an hour to 1.6.
While the home’s energy use was greatly reduced, it didn’t meet the extremely low Passive House standard of 15 kWh per square meter, putting the house in a “sort of purgatory” when it came to heating, Wong said. The home wasn’t efficient enough to do away with a traditional heating system, but was too efficient to justify the cost of implementing it. Wong settled on reusing existing radiators, with supplementary radiant floor heating in the basement and master bath.
A 94% efficient UltimateAir energy recovery ventilator that runs on the same amount of power as a light bulb does much of the work of keeping the house comfortable. The ERV feeds ducts in each room to keep the temperature the same throughout the house. A tiny air-conditioning unit in the stairway is enough to cool the home in the summer.
The Rosedale house also includes a number of features that save energy on hot water production. A German Latento XXL passive solar-adapted hot tank heats water only 12 hours per day, running in off-peak hours when Toronto’s electric rates are lower. During peak usage times, a recirculation loops sends cold water back to the tank, providing immediate hot water to the user.
Wong completed the preliminary work for LEED-Platinum certification for the project, but she says landscaping is holding her back a few points. The certification is on hold for the time being. Meanwhile, Wong showed the house off to an impressed crowd during the Greenbuild conference in October. The biggest lesson she’s hoping to pass on is to do no-brainer renovations like improved windows and insulation before spending on other energy upgrades.
“Put your money where it’s important, in the exterior wall,” she says. “It’s going to be there for 100 years.”
Jeffrey Lee is Managing Editor of EcoHome.