We’re Working With Sidewalk Labs to Tame Toronto Weather

Name: RWDI Consulting Engineers and Scientists
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The urban innovation firm Sidewalk Labs is envisioning “a new kind of neighbourhood” in Toronto. Since being chosen as an innovation partner by Waterfront Toronto, a government agency responsible for waterfront revitalization, Sidewalk Labs has proposed new approaches to everything from building materials to transportation. But Torontonians – accustomed to frigid winters and sticky summers – might take special note of Sidewalk Labs’ goal of taking the edge off the weather.

RWDI has been working alongside Partisans Architecture, BBB Architects, and Public Work (landscape architects) to help Sidewalk Labs identify ways to significantly increase the annual number of “thermally comfortable” daytime hours in Toronto’s Quayside neighbourhood.

Winter is coming – but good design can help

No one expects winter in a northern city to feel like summer. But it is possible to introduce passive strategies that make outdoor spaces comfortable earlier in the spring, later in the fall, and for more hours of the day. Mitigating the most uncomfortable conditions can make a meaningful difference for residents, businesses and shared space:

A restaurant can boost revenue if it can open its patio earlier in spring and close later in fall.
A public square can be used for a greater variety of community events if the local climate is more predictable and controllable.
Residents will be more motivated to walk and cycle if conditions are more comfortable.

Applying RWDI’s climate insights on Toronto’s waterfront

Since Sidewalk Labs engaged us in early 2018, we’ve worked with our partners on the outdoor comfort team to develop dozens of passive strategies for mitigating uncomfortable weather conditions on Toronto’s waterfront. Passive strategies moderate people’s experience of weather and climate while consuming little or no energy.

On cold days, key ways to promote thermal comfort include reducing convective heat loss and maximizing the amount of solar radiation people are exposed to. In other words, offering protection from the wind and helping people to feel more of the sun’s warmth.

On hot days, the opposite conditions become desirable. People seek out the cooling shade, and breezes are welcome since air movement goes a long way to making people feel cooler, especially when humidity is high.

Thermal comfort conditions without and with passive climate control.

Thermal comfort conditions without (left) and with (right) passive climate control.

In addition to developing numerous strategies for wind and sun management, our team has carried out computational fluid dynamics (CFD) and solar modeling work to validate the efficacy of each approach – first modeling the baseline weather and climate conditions in the Quayside neighbourhood, and then assessing how our interventions would affect human experience. Although we can’t control the seasons, we estimate that passive control measures are implemented, it’s possible to more than double the number of comfortable daylight hours each year for key spaces – from about 30% to 74%. The chart below gives an overview of the broad types of uncomfortable conditions we focused on managing.

An innovative “raincoat” to promote outdoor comfort

Raincoat structure under construction — Raincoat prototype under construction at the 307 building site (image courtesy of Sidewalk Labs)

One notable solution we developed, along with our partners in the outdoor comfort team assembled by Sidewalk Labs, is a second skin or "Raincoat" that can be applied to the bottom of a building’s edge to offer protection from the elements.

The Raincoat system can be adapted to promote thermal comfort in both summer and winter. Like a real raincoat, the barrier can be kept open for greater ventilation or closed for greater protection. The membrane can also be made more or less transparent. Each of these adjustments helps to vary the conditions underneath the Raincoat – promoting increased air movement for summer cooling, reducing the windspeeds occupants experience on chilly winter days, and managing the sun to help moderate conditions along the base of the building.

Our analysis revealed a number of ways to optimize the effectiveness of the Raincoat in different conditions. A few specific examples:

Increasing the depth of a Raincoat increases the amount of wind passing below the Raincoat, promoting cooling breezes on hot summer days.
If a Raincoat is recessed from the building edge, winds are deflected off the exposed building façade and enter under the Raincoat – again, supporting human comfort with improved air circulation.
A higher attachment point for a Raincoat helps to reduce wind speeds, promoting more moderate conditions inside the Raincoat on cool, breezy days.
Downwashing, the movement of air down the façade of a building, can create uncomfortable conditions in spaces adjacent to the structure. A Raincoat can provide protection from this effect, especially when used in combination with a podium at the base of the building.

A more comfortable urban grid

When a neighbourhood and its infrastructure have already been constructed, adaptations for promoting thermal comfort have to fit into an existing built environment. These can range from passive additions like shades and canopies to active interventions like heat lamps. But when a neighbourhood is being built from the ground up, there’s an enormous opportunity to design the street grid itself to support human comfort. Designers can use the size and orientation of streets and structures to create pleasant wind, solar and thermal conditions.

Hierarchical strategy for thermal comfort — Hierarchical strategy for improving thermal comfort in a neighborhood.

RWDI’s design team explored several design options for a possible street grid in the neighbourhood Sidewalk Labs is envisioning. The graphics below offer a colour-coded visualization of wind velocity in two of the possible grid configurations: Phototrope and Phototrope v2.

Both configurations are more organic than a typical rectilinear street grid. The Phototrope configuration has oblique streets, which aim to reduce wind penetration from east and west winds. The second version of the configuration (Phototrope v2) reorients the streets, but breaks them up, reducing long thoroughfares. As the graphics show, both configurations successfully reduce wind speeds in the development. This is particularly evident for winds from the east and west, the prevailing winds along Toronto’s lakeshore.

Wind patterns by direction CFD images — Street grid, orientation and size of buildings has a significant impact on wind, solar and thermal comfort conditions. Both building configurations, Prototype and Prototype V2, are more organic than the traditional street grid to reduce wind speeds.

Start early

As with many design challenges, the earlier a team can incorporate thermal comfort into their planning the more options they have for creative and cost-effective adaptations. End-of-process adaptations, up to and including energy-intensive climate control systems, may be necessary to maintain reasonable conditions once a development has been built. But as our work with Sidewalk Labs and other partners shows, many exciting opportunities exist in earlier planning stages to incorporate thermal comfort into the fundamentals of a project’s design.