The City of Denver has some great initiatives to reach its sustainability goals by 2020. From air quality to public health, Denver has worked hard to lay a foundation that will not only reduce the impact of the City, but maintain a more sustainable community. Here at Sow Green, we know that the installation of more green roofs will help us get there. Let us take a look at some of the City’s goals and find out how:
Air Quality Goal: Attain all National Ambient Air Quality Standards
More green spaces in Denver could mean more vegetation to filter pollutants from the air. A study in Toronto found that 58 metric tonnes of air pollutants could be removed if all the roofs in the city were converted to green roofs (Currie and Bass, 2008). The level of reduction in pollution depends on the type of vegetation and roof design, with extensive green roofs having a lower impact than intensive ones. Another series of modeling studies in Chicago showed 1675 kg of pollutants being removed by 19.8 hectares of green roofs in one year (Yang et al. 2008).
Climate Goal: Reduce Denver CO2 emissions to below 1990 levels
Green roofs can affect the ambient CO2 levels in the atmosphere, offsetting the emissions rate of the city of Denver (Li et al. 2010). By installing more green roofs, Denver can be closer to it’s goal of lowering and maintaining CO2 levels.
Energy Goal: Hold total energy usage below 2012 levels, while cutting fossil fuels by 50%
Green roofs reduce the heat island effect in urban areas as well as reduce energy costs by insulating the building below. Heat flux can be reduced by as much as 72% in the summer. Through thermal resistance green roofs can reduce energy costs by up to 33% in the winter (Miller, Charlie, et al. 2011). Green roofs also raise the performance of solar energy installations in comparison with a traditional black top roof (Alshayeb and Chang, 2016).
Food Goal: Grow and/or process at 20% of food purchased in Denver in Colorado
Green roofs make excellent urban agriculture centers since they are more controlled environments, removed from the majority of insects and wildlife, as well as the spread of disease. Hospitality developments such as restaurants and hotels can use green roofs to grow their own produce. Rooftop gardens in residential developments can also reduce the area of food deserts in urban neighborhoods.
Health Goal: Increase the % of youth in Denver at a healthy weight from 69% to 74%
Green roofs can pose as recreational space in urban areas with little to no green space. Studies have shown that green spaces in urban environments increase physical activity of residents and reduce health costs (Cicea and Pirlogea, 2011). By increasing the number of green roofs in residential and mixed-use development, Denver can increase the health of children by ensuring access to safe outdoor spaces.
Housing Goal: Ensure 80% of neighborhoods are rated as affordable
Since green roofs can reduce energy costs in both the summer and winter, residential developments with green roofs are more affordable to live in.
Water Quality Goal: Make all Denver creeks and rivers swimmable and fishable
Depending on the depth of the growing medium, green roofs can retain anywhere from 50-80% of stormwater, reducing the amount of pollutants in our rivers and streams (Miller, Charlie, et al. 2011).
As you can see, greens roofs have many sustainability benefits for both residents and the surrounding community. If Denver is going to hit its sustainability goals, increasing green spaces and retrofitting roofs with vegetation and solar energy is a solution that has a big bang for its buck.
CURRIE, B.A. & BASS, B. (2008) Estimates of air pollution mitigation with green plants and green roofs using the UFORE model. Urban Ecosystems 11: 409 - 422.
YANG, J., YU, Q. & GONG, P. (2008) Quantifying air pollution removal by green roofs in Chicago. Atmospheric Environment 42: 7266 -7273.
CICEA, C., & PÎRLOGEA, C. (2011). GREEN SPACES AND PUBLIC HEALTH IN URBAN AREAS. Theoretical and Empirical Researches in Urban Management, 6(1), 83-92. Retrieved from http://www.jstor.org/stable/24873277
Li J.F., Wai O., Li Y.S., et al., Effect of green roof on ambient CO2 concentration, Building and Environment. 45, 2644-2651 (2010).
Miller, Charlie, et al. The Benefits and Challenges of Green Roofs on Public and Commercial Buildings. United States General Services Administration, 2011, The Benefits and Challenges of Green Roofs on Public and Commercial Buildings, www.gsa.gov/cdnstatic/The_Benefits_and_Challenges_of_Green_Roofs_on_Public_and_Commercial_Buildings.pdf.
Mohammed Alshayeb, Jae D Chang, Photovoltaic Energy Variations Due to Roofing Choice, Procedia Engineering, Volume 145, 2016, Pages 1104-1109, ISSN 1877-7058, https://doi.org/10.1016/j.proeng.2016.04.143. Retrieved at: http://www.sciencedirect.com/science/article/pii/S1877705816301497