Hamilton Green Roof Project

Zargham Ahmed, Samin Lu-Sullivan, Maia Moore, Keshikaa Suthaaharan

What Are Green Roofs?

Climate change is a pressing issue around the world, and cities have begun focusing on advocating for the use of green roofs to increase the amount of green space and to mitigate some of the effects of climate change within urban environments. A green roof is any layer of vegetation that is planted on flat or slightly slanted roofs, and is composed of layers as shown in Figure 1 (NPS, 2021; Green Infrastructure Ontario, 2020). There are three different types of green roofs: intensive, semi-intensive, and extensive. They differ based on the depth of the substrate and the type of plants grown (Table 1) (Manso et al., 2021). When designing green roofs, the location of implementation, the type of green roof and the plants used must be considered to optimize the benefits. We have decided to propose the implementation of green roofs in Hamilton, ON, to promote the use of green roofs in smaller urban centers within Canada.

Figure 1: Seven layers required for green roofs construction (Adapted from Suszanowicz and Kolasa Więcek, 2019; vecteezy-pngs, n.d.).

Table 1: Soil depths and types of plants that can be grown on different types of green roofs (Shafique, Kim and Rafiq, 2018; Manso et al., 2021).

Summary of the Impacts of Green Roofs

Green roofs have multiple positive effects on urban environments. They can act as an alternate source of income through the implementation of urban agriculture and can save money through reduction of heating and cooling costs (Manso et al., 2021; Mui, 2011). Green roofs contribute to the reduction of the UHI effect, absorb CO2 and pollutants, and promote more natural hydraulic processes within urban environments (Suszanowicz and Kolasa Więcek, 2019; Mui, 2011; Manso et al., 2021; Li and Babcock, 2014; Peng and Jim, 2015; Palla, Gnecco and Lanza, 2010; Bianchini and Hewage, 2012). Furthermore, the presence of green roofs provides habitats and refuge for pollinators and bird species within dense urban environments (Brenneisen, 2006; Mayrand and Clergeau, 2018; Kratschmer, Kriechbaum and Pachinger, 2018). Additionally, the development of additional green space in urban areas improves psychological well-being and provides educational opportunities for residents (The Calhoun School, 2021; Loder, 2014). In summary, green roofs can provide numerous economic, environmental, ecological and social benefits to Hamilton citizens.

Proposed Strategy in Hamilton

Through the comprehensive review of the available literature, we propose the implementation of intensive green roofs in developing regions of Hamilton, outlined in Figures 2 and 3. Though intensive green roofs are more and require more maintenance than other types of green roofs, they have numerous social, economic and environmental benefits. Importantly, intensive green roofs have a thick substrate layer which supports greater biodiversity than thinner substrate layers (Brenneisen, 2003; 2006). We further propose that the substrate surface of these green roofs should be designed with varying thicknesses and should incorporate natural soil substrates to promote biodiversity (Brenneisen, 2006).

We will use community engagement to offset some of the maintenance and operational costs associated with intensive green roofs. To do this, we propose growing agricultural crops and developing educational and community programs to promote public engagement in developing regions in partnership with youth organizations and soup kitchens. Green roofs would allow Hamilton residents to reap the many psychological benefits associated with increased green spaces.

We propose that the City of Hamilton implement the following legislation, similar to that of Toronto (City of Toronto, 2021), to increase the implementation of green roofs within Hamilton:

Requiring implementation of green roofs on all buildings over a certain size.
Incentivize the construction of green roofs through tax reduction and rebates.
Provide financial support landowners developing green roofs.
Provide standards for the structure and engineering of green roofs.

Figure 2: Regions of recent development in the greater Hamilton Area, outside of the downtown area. These developing areas are good locations for the beginning of the proposed green roof project (City of Hamilton, 2020a; b).

Figure 3: Sites of planned development in the regions outlined in Figure 2. The areas marked by red/orange are specific lots where new condominiums or apartment buildings are being constructed (City of Hamilton, 2020a; b).

References

Bianchini, F. and Hewage, K., 2012. Probabilistic social cost-benefit analysis for green roofs: A lifecycle approach. Building and Environment, 58, pp.152–162.

Brenneisen, S., 2003. The benefits of biodiversity from green roofs-key design consequences. 1st North American Green Roof Conference: Greening Rooftops for Sustainable Communities, pp.323–329.

Brenneisen, S., 2006. Space for Urban Wildlife: Designing Green Roofs as Habitats in Switzerland. Urban Habitats, 4, pp.27–36.

City of Hamilton, 2020a. Urban Residential Subdivisions: Glanbrook. Available at: https://www.hamilton.ca/sites/default/files/media/browser/2020-05-04/subdivision-condo-development-glanbrook-2019.pdf.

City of Hamilton, 2020b. Urban Residential Subdivisions: Stoney Creek. Available at: https://www.hamilton.ca/sites/default/files/media/browser/2020-05-04/subdivision-condo-development-stoney-creek-2019.pdf.

City of Toronto, 2021. Eco-Roof Incentive Program. [online] Toronto. Available at: https://www.toronto.ca/services-payments/water-environment/environmental-grants-incentives/green-your-roof/ [Accessed 3 Mar. 2021].

Green Infrastructure Ontario, 2020. Green Roofs. [online] Green Infrastructure Ontario. Available at: https://greeninfrastructureontario.org/green-roof/ [Accessed 5 Mar. 2021].

Kratschmer, S., Kriechbaum, M. and Pachinger, B., 2018. Buzzing on top: Linking wild bee diversity, abundance and traits with green roof qualities. Urban Ecosystems, 21(3), pp.429–446.

Li, Y. and Babcock, R.W., 2014. Green roofs against pollution and climate change. A review. Agronomy for Sustainable Development, 34(4), pp.695–705.

Loder, A., 2014. ‘There’s a meadow outside my workplace’: A phenomenological exploration of aesthetics and green roofs in Chicago and Toronto. Landscape and Urban Planning, 126, pp.94–106.

Manso, M., Teotónio, I., Silva, C.M. and Cruz, C.O., 2021. Green roof and green wall benefits and costs: A review of the quantitative evidence. Renewable and Sustainable Energy Reviews, 135, p.110111.

Mayrand, F. and Clergeau, P., 2018. Green Roofs and Green Walls for Biodiversity Conservation: A Contribution to Urban Connectivity? Sustainability, 10(4), p.985.

Mui, S.C.M., 2011. Green roof urban farming for buildings in high-density urban cities. [online] Hainan China World Green Roof Conference. Haninan (Haikuo, Boao and Sanya), China. Available at: https://www.researchgate.net/profile/Sam-C-M-Hui-2/publication/228933623_Green_roof_urban_farming_for_buildings_in_high-density_urban_cities/links/5416b2460cf2788c4b35df4e/Green-roof-urban-farming-for-buildings-in-high-density-urban-cities.pdf.

NPS, 2021. What is a Green Roof? [online] Available at: https://www.nps.gov/tps/sustainability/new-technology/green-roofs/define.htm [Accessed 5 Mar. 2021].

Palla, A., Gnecco, I. and Lanza, L., 2010. Hydrologic Restoration in the Urban Environment Using Green Roofs. Water, 2(2), pp.140–154.

Peng, L.L.H. and Jim, C.Y., 2015. Economic evaluation of green-roof environmental benefits in the context of climate change: The case of Hong Kong. Urban Forestry & Urban Greening, 14(3), pp.554–561.

Shafique, M., Kim, R. and Rafiq, M., 2018. Green roof benefits, opportunities and challenges – A review. Renewable and Sustainable Energy Reviews, 90, pp.757–773.

Suszanowicz, D. and Kolasa Więcek, A., 2019. The Impact of Green Roofs on the Parameters of the Environment in Urban Areas—Review. Atmosphere, 10(12), p.792.

The Calhoun School, 2021. Green Roof Learning Center. [online] The Calhoun School. Available at: https://www.calhoun.org/about/calhoun-glance/green-roof [Accessed 27 Feb. 2021].

vecteezy-pngs, n.d. Grass [image online] Available at: https://www.vecteezy.com/png/1193359-grass [Accessed 06 March 2021]