Sensing Our Way to Better Buildings

One of the many difficult truths about climate change facing Torontonians is that the energy used to heat and cool buildings, such as apartments and condo towers – as well as schools and shopping malls – account for more than half of the city’s greenhouse gas emissions (according to its Zero Emissions Buildings Framework, published in 2017). As all cities try to reduce their carbon footprint, they will need to draw on the latest innovations from fields such as architecture, engineering and materials science.

A piece of the solution may be taking shape in Hamilton, Ontario, where Toronto’s ERA Architects has embarked on a full-scale retrofit of an apartment building known as Ken Soble Tower. As part of the overhaul, the 50-year-old building will receive new, high-efficiency windows, additional insulation, and state-of-the-art ventilation and humidity controls.

A critical element of the project is a system of sensors that are monitored in the lab of Marianne Touchie, an assistant professor in U of T’s department of civil and mineral engineering. Touchie oversees a team of graduate students that has been experimenting with sensors as a means of tracking a building’s energy performance and thermal levels, and the impact these two elements have on residents’ health and comfort.

Big buildings are complex organisms, and occupants can unknowingly undermine conservation efforts by leaving windows open or by overriding automated thermostats. “We need to think about the building as a system,” says Touchie, noting that real-time performance data can drive adjustments that further reduce energy use and improve residents’ comfort. The Ken Soble Tower’s design is expected to slash the building’s greenhouse gas emissions by as much as 94 per cent. “It’s a benchmark project for pushing things as far as they can go,” says Graeme Stewart (BA 2004 St. Mike’s, MArch 2007), a partner at ERA.

The data from the sensors to be deployed at Ken Soble Tower have the potential to improve the energy efficiency and comfort of newer buildings as well. Over the past few decades, more than 1,000 new condo towers have sprung up in Toronto. A surprising number of them are energy hogs, due to a steel-and-glass design that makes them difficult to heat and cool properly. “They weren’t built with the environment foremost in mind, that’s for sure,” says Touchie.

Helen Stopps, a PhD candidate in mechanical and industrial engineering who works with Touchie, is investigating the use of smart thermostats (manufactured by Toronto-based Ecobee) as a low-cost way of improving energy efficiency in these newer structures. Smart thermostats use an algorithm to set the indoor temperature, based on sensors that detect the presence of people in the suite and exterior temperature. Using data gathered from 57 apartments in a pair of condo buildings constructed within the past decade, Stopps found that the smart devices reduced energy consumption by an average of 10 per cent.

“It’s a low-cost way of making a dent in the energy consumption of those towers without changing the building envelope or ventilation system,” says Touchie. After all, newer condo towers are probably decades away from requiring a major refurbishment. And condo boards in newer structures will not have built up sufficient reserve funds to address building-wide shortcomings such as drafty windows or overheating in south- and west-facing units.

Touchie points to another finding from a study by Jamie Fine, a post-doctoral researcher, which proposes a different sort of interim move to cut heating costs in buildings that don’t have in-suite thermostats. In large apartment buildings, retrofitting every unit with smart thermostats may not be cost-effective. But Fine’s study found that grouping apartments into zones and installing fewer sensors within those zones also led to energy savings. The proposal would optimize temperatures within each group of suites, rather than within individual units. The study, using data from one Toronto building, projects that such changes could reduce energy consumption by 14 per cent within a 10-year payback period for the associated capital costs.

These projects highlight the significance, from both a sustainability and a quality-of-life perspective, of knowing how large structures actually function. Touchie suggests that the next generation of highrises could be equipped with both sensor systems that continually feed performance measures into a dashboard, as well as trained managers who know how to interpret the data.