Green roofs are wise investments that pay off

The pandemic and climate emergency are forcing cities around the world to rethink how they develop and operate.

As part of World Green Roof Day, June 6, we are prompted to reflect on the contribution that multi-functional green roofs offer to social, economic, health and ecological well-being. Even without specific incentives or policy mechanisms, Vancouver holds a place of leadership and excellence with regards to green roof technology.

In response to this once-in-a-lifetime call to accelerate the change required in Canadian cities, we make the case here for large-scale green roof implementation as an elegant and integrated response that grants resiliency, security and well-being at all scales.

With much of the population in lockdown, the health and social requirements of open green spaces and access to nature are crucially important. In Vancouver, the social distance rules designed to keep us safe reveal layers of consideration.

Given the limitations at ground level, we call on developers, urban planners, landscape architects and architects to act on the opportunity offered by the roofscape of future and current buildings.

Whether “intensive”accessible roof gardens, or shallow “extensive” installations where low-maintenance plantings replace gravel ballast, the therapeutic and healing value of green roofs, both accessible and visible, is well documented. While 75 per cent of new commercial projects have extensive green roofs, policy incentives would help advance the residential market.

The research quantifying green roof performance in coastal B.C. complies with international science and standardized methods. Local results clearly demonstrate the effectiveness of green roofs on stormwater runoff, thermal insulation, acoustical and urban ecology. Data from Vancouver Public Library, BCIT Green Roof Research Facility, Electronic Arts, and City of White Rock Operations Building validate that green roofs significantly reduce runoff entering stormwater infrastructure and aquatic ecosystems, and reduce daily energy demand.

In most cases, planted green roofs outperform low-profile roll out mats.

Field measurements on the living roof of the Vancouver Conference Centre align with BCIT acoustics research that plant communities with varying root structures increase sound absorption. For methods, data, results and general information on green roofs in our region, visit the BCIT Centre for Architectural Ecology website.

Green roof systems are excellent investments, and cost savings are most effectively captured when green roofs are integrated into the design and construction processes of a building. The cost to supply, install and establish an extensive green roof starts at $16 per square foot, yet the favourable return on investment is sometimes erroneously abandoned due to value engineering. Thus lost are the numerous and overlapping benefits with respect to energy, stormwater, acoustics, secured green space, biodiversity, agriculture potential, protection of membrane, and the health benefits to citizens.

Incorporating a green roof into a building concept respects its integral role to the rest of the building envelope and mechanical systems. In such a case, owners and designers are faithful to protect this element that preserves the footprint of their building vis-à-vis its users, the community, and the environment, while also improving the efficiency, sustainability, aesthetics and attractiveness of their building. The GreenSave

calculator is a tool that illustrates the return on investment and life-cycle cost of green versus conventional roofing.

Just as Dr. Bonnie Henry has called on various social rules to bend the curve on COVID-19, we call on decision-makers in Vancouver and region to include more green roofs in the built environment. With so many benefits to health and well-being, to climate resilience, environmental protection, and to our local economy, encouraging and promoting multi-functional green roofs is an investment with guaranteed returns.

Policy leadership and collaborative excellence are essential if the future of our cities is to be brighter, healthier and greener.