As part of an aggressive action plan designed to reduce greenhouse gas emissions by 80 percent by 2050, the City of Toronto established The Eco-Roof Incentive Program in 2009 to drive the installation of green roofs and cool roofs.
A cool roof or white roof is a roofing system with an exterior surface that reflects the sun’s rays and reduces heat build-up from the sun’s thermal energy. A cool roof can be either a coating applied over an existing roof system or a new waterproofing membrane.
Green roofs, also known as living roofs or vegetated roofs, support the growth of vegetation.
The impact of the Eco-Roof Incentive in Toronto is significant. To date, the program has supported more than 627 eco-roof projects, creating a combined green roof and cool roof area exceeding 1.14 million square metres.
Rebates of up to $100,000 are available to property owners who install green roofs on their buildings and up to $50,000 for cool roof installations. Beyond the financial incentive, eco-roofs offer numerous advantages to property owners and have significant environmental benefits.
What’s So Cool About Cool Roofs?
Reducing greenhouse gas emissions and improving energy efficiency in the building sector are key considerations in the industry’s efforts to mitigate climate change.
Roofs, often overlooked, contribute significantly to both cooling and heating energy loads in buildings. Traditional roofing materials absorb and radiate heat, elevating temperatures in urban areas. Compared to traditional roofing, cool roofs offer an effective solution to reduce cooling demand in buildings.
Cool Roofing is Not a New Concept
Cool roofing has been used by building owners and roofing contractors for many years on commercial, industrial and residential buildings. They can be installed on low-slope roofs (typically found on commercial, industrial and office buildings) or the steep-sloped roofs used on residential buildings.
A cool roof, using highly reflective materials, is designed to reflect sunlight so that less heat is absorbed by the building. Cool roofs can be achieved using a variety of roofing technologies, including single-ply membranes, asphalt systems, and metal roofing panels.
For example, cool aluminum roofing panels come in a variety of architectural profiles to suit any residential or commercial application, giving owners flexibility in style and performance.
A cool roof can be either a coating applied over an existing roof system or a new waterproofing membrane.
Not All Cool Roofs Are White
With today’s technologically innovative systems, a cool roof does not have to be white. There are many options available: red aluminum shingles, brown asphalt, metal panels. The most popular roof shingle colours in 2024 are earth tones and cool greys, offering aesthetic versatility to complement different residential styles. A wide variety of roof coatings can also be applied to existing rooftops to achieve solar reflectivity.
Replacing the conventional practice of installing dark-coloured roofs, which absorb and transfer solar heat into the building, cool roofs are one of the easiest and low-cost ways to improve resilience and energy efficiency.
Benefits
By reflecting the sun’s energy, cool roofs can keep buildings far cooler than traditional roofs. A cool roof can reduce the amount of energy needed for air conditioning by up to 15 percent on a single-storey building, leading to substantial savings on energy bills as well as increasing occupant comfort levels.
Cool roofs are an effective way to save energy and lower utility costs while reducing a building’s carbon footprint. Other benefits include reducing the overall temperature of entire cities (urban heat island effect), decreasing peak energy demand, heat-related illnesses, and roof maintenance costs.
Research shows that a white roof of 1,000 square feet can offset 10 tons of carbon dioxide over its 20-year lifetime, compared to a black roof. Whitening all eligible urban flat roofs on the planet would prevent 24 Gigatonnes of CO2 emissions, the equivalent of taking 300 million cars off the road for two decades.
For even more benefits, green roofs are another option to consider. Green roofs reduce building energy use by cooling roofs and providing shading, thermal mass and insulation. They also reduce stormwater runoff and the risk of urban flooding. Adding a green roof can transform a multi-residential or office building into aesthetically and sustainable spaces, promoting well-being.
Visit the Eco-Roof Incentive Program webpage at toronto.ca/EcoRoof or email at ecoroof@toronto.ca.