ZERO SUM

Taking a community approach to sustainable energy

Just as net zero describes energyefficient dwellings that produce at least as much energy as they use, so too does the term apply to the net-zero energy (NZE) neighbourhood. It’s simply on a larger scale, where all of a community’s dwellings rely on combined heat and power systems from one centralized source known as district heating.

NZE is a more feasible goal at the community level than it is for an individual dwelling. Although solar heating is easier to set up in a rural or suburban home, the auto usage and attendant infrastructure in such settings can counteract the project’s sustainable impact. All things considered, urban neighbourhoods are able to most efficiently support alternative and combined power sources, in part because the maintenance needed to support sustainable energy in many homes is limited to one plant.

Many strategies used in designing net-zero dwellings are transferable to the planning of an NZE neighbourhood. While local wind patterns, sun orientation, topography, ground depth of winter frost, and shadows from other buildings and trees all play a part, many of these factors are more easily managed when designing at the community scale. For example, on a district scale, one can more readily anticipate and change the topography and orientation of a street layout to take advantage of the winter sun and limit the summer heat. zHome in Issaquah Highlands, Washington State, became the first American net-zero, carbon-neutral development when it opened in 2011. Designed by David Vandervort Architects, every aspect of the community, including the building process, was designed to minimize energy consumption and carbon emissions. Its most noticeable feature is a series of roof-mounted photovoltaic panels. These add considerably to the aesthetic quality of the 10 townhomes, with the roofing size calculated to house the exact number of photovoltaic panels needed for NZE consumption.

The 10 units are tied into the local electric grid. In summer, the panels produce more energy than zHome residents require, with the excess fed into the local grid to be used by the wider community. In the winter, the panels produce less energy than is needed, and so the grid assists in supplying energy. This relationship benefits both parties and allows zHome to have NZE usage without the need for extensive facilities to store excess energy.

High-quality insulation procedures reduce heating and air-conditioning costs. Featuring extremely high-quality panes, windows are tightly sealed. Fresh air is pumped into the house via heat-recovery ventilation. On top of all this, heating and AC employ a groundsource heat pump system.

While some of the high-tech features, necessary to ensure sustainability, might detract from the community feel of the development, several features were installed to encourage neighbourly interaction, including a central courtyard, around which the units are laid out.

Ontario developers are following suit. Land Ark Construction’s walkable Watercolour Westport community, Canada’s first NZE-ready neighbourhood, broke ground in Brockville in August. Near Ottawa, Zibi, a 34-acre, carbon-neutral development, will harness a district energy system to eliminate greenhouse gas emissions from building heating and cooling operations by leveraging locally generated hydroelectricity. And in London, Sifton Properties’ West 5 development is a 70-acre multi-use community that will serve as a demonstration site for the new community net metering.

AVI FRIEDMAN IS AN ARCHITECT, PROFESSOR, AUTHOR AND SOCIAL OBSERVER. AVI.FRIEDMAN@MCGILL.CA