SAB HOMES 5 - Wood Avenue House

Large Georgian home leaves small enviro footprint

Ottawa’s first LEED Platinum detached house is located in the city’s upscale Rockcliffe Park neighbourhood northeast of downtown. It replaces an older, much modified and energy inefficient home that the owners had occupied for many years.

By Linda Chapman

The decision to build new rather than renovate was not taken lightly, with the owners even offering to sell the house for $1 to anyone prepared to remove it from the site. In the end, uncertainty about renovation costs, doubts about ultimate energy performance, and the knowledge that most of the existing building fabric could be recycled tipped the scales away from renovation in favour of new construction.
Dismantle and build

From that point forward the owners’ objective was to create a spacious and elegant house with the minimum possible environmental footprint. They also wanted a traditional design adaptable to their needs as they aged. The house has an area of 4,300sf, including four bedrooms and generous living spaces arranged on two floors above a partial basement. The existing house was carefully dismantled, the materials separated and sent to be recycled – except for the concrete slabs which were crushed and used as a base for the new structure. When choosing new materials, the challenge was to balance low environmental impact and durability, so the selection criteria included:
• sustainably-produced natural materials such as FSC [Forest Stewardship Council] certified wood;
• locally-produced materials that would minimize transportation energy, such as stone, brick and tiles from Quebec; and
• low-toxicity products for interior furnishings, fixtures and finishes such as paints with low or no VOCs [volatile organic compounds].
The construction is ICF [insulated concrete forms] for the basement walls, with 2×6 framing for the upper floors. Innovative truss design enabled stud spacing to be increased to 24in [rather than the usual 16in] minimizing the material required, increasing the area of voids available for insulation, and improving overall wall performance.Soy-based spray insulation was used, achieving an R-value of 50.
Windows are triple glazed on the north elevation, but only double glazed elsewhere in order to maximize the opportunities for passive solar heat gain in the winter. Prior to the installation of drywall and other finishes the building envelope was tested for air leakage and any weak points sealed.

Heating and cooling

The house is heated and cooled by a primary geothermal system that circulates water through a 450ft deep loop drilled beneath the driveway. The system utilizes the stable sub-surface temperature of the earth to minimize the input energy necessary to heat or cool water for the in-floor radiant system. The additional heating or cooling required is supplied by a highly efficient heat pump.
The radiant system is divided into multiple zones, enabling heating or cooling to be adjusted to the needs of each area of the house, and turned down or off if areas are unoccupied. A forced air back-up system is also installed to provide additional heating and cooling in extreme weather. A rooftop cupola brings light into the centre of the house, and has operable windows that exhaust hot air. An HRV [heat recovery ventilator] removes heat from the stale air as it is exhausted from the house.
The high-performance building envelope and efficient heating and ventilation system together with high efficiency CFL and LED lighting contribute to an estimated 75% savings in purchased energy, and an EnerGuide rating of 88 [compared to the building code requirement of 65 to 72].

Water conservation

Water conservation was also a concern, but in the end had to be limited externally to rainwater capture and reuse for irrigation, and internally to dual flush, low-flow and touch-sensitive fixtures. Grey water recycling for other uses was also investigated but there are still impediments at the regulatory level because of concerns about cross contamination.
Rainwater collected from the roof is directed to a series of basement storage tanks that supply the ‘smart’ irrigation system. This system is controlled by a weather station that supplies water to shady and sunny parts of the garden according to need as determined by the data collection software.
The building is designed for a long life, but also to adapt to the changing needs of the owners as they age. To this end, steps and stairs are designed with  a lower than standard rise; plumbing has been roughed in for a downstairs shower should this ever become necessary; electrical outlets are placed higher than standard to minimize the need for bending; and there is space available for the future installation of an elevator.

LEED for Homes and House Size
The LEED Canada for Homes rating system requires a minimum level of performance through prerequisites, and rewards improved performance in eight different categories. Because large homes use more energy and resources than small homes, they are required to achieve a higher overall standard in order to receive a particular LEED rating: Certified, Silver, Gold or Platinum. The system includes a home size adjustment mechanism that subtracts credits from homes with areas that exceed a prescribed maximum for the number of bedrooms provided.
The Wood Avenue house is classified as having 5,290sf. This includes 925sf of finished basement. We were advised to classify the house as having seven bedrooms. There are four bedrooms on the second floor. The library on the second floor is classified as a fifth bedroom, and there are two potential bedrooms in the basement. We were penalized 8.5 points for this size of house.

Linda Chapman B. Arch., OAA, MRAIC, LEED AP, is Principal of Linda Chapman Architect


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