Title: Reading and Audio-Visual Assignments
Course: GFM 103 Exterior Environmental Management > Section: GFM 103 Exterior Environmental Management

Reading and Audio-Visual Assignments

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Cooling Down the Heat Islands

Vegetative roofs, also known as green roofs, are thin layers of living vegetation installed on top of conventional flat or sloping roofs. We have chosen to use the word "vegetative" rather than the word "green" in this guide because a non-vegetative roof could be considered to be environmentally "green" without being vegetative. For example, due to it being white and therefore mitigating heat gain within the building and reducing heat island contribution, a white non-vegetative roof might be considered as being "green" or environmentally friendly. In other words, "green" has too broad of a connotation to be clear for use in this guide, and we recommend that the industry adopt the nomenclature "vegetative," rather than the overly broad "green."

Vegetative roofs are divided into two categories: 1) extensive vegetative roofs, which are 6 inches or shallower and are frequently designed to satisfy specific engineering and performance goals, and 2) intensive vegetative roofs, which may become quite deep and merge into more familiar on-structure plaza landscapes with promenades, lawn, large perennial plants, and trees. With respect to the vegetative overburden, this guide addresses only the more shallow extensive vegetative roofs.

The extent to which urban areas can benefit from heat island reduction strategies depends on a number of factors—some within and some outside of a community's control. Although prevailing weather patterns, climate, geography, and topography are beyond the influence of local policy, decision makers can select a range of energy-saving strategies that will generate multiple benefits, including vegetation, landscaping, and land use design projects, and improvements to building and road materials.
- Trees, vegetation, and green roofs can reduce heating and cooling energy use and associated air pollution and greenhouse gas emissions, remove air pollutants, sequester and store carbon, help lower the risk of heat-related illnesses and deaths, improve stormwater control and water quality, reduce noise levels, create habitats, improve aesthetic qualities, and increase property values.
- Cool roofs can lower cooling energy use, peak electricity demand, air pollution and greenhouse gas emissions, heat-related incidents, and solid waste generation due to less frequent re-roofing.
- Cool pavements can indirectly help reduce energy consumption, air pollution, and greenhouse gas emissions. Depending on the technology used, cool pavements can improve stormwater management and water quality, increase surface durability, enhance nighttime illumination, and reduce noise.

Using these strategies in combination can enhance their effectiveness. For example, installing a permeable pavement parking lot that includes shade trees can extend the longevity of the pavement and vegetation.

Widespread implementation of these strategies also provides additional benefits. For example, a single cool roof will mainly result in benefits to the building owner and occupants. Community-wide cool roof installations, though, will provide savings to the building owner and occupants and to the community at large, as a large number of cool roofs can reduce air temperatures, resulting in multiple benefits associated with cooler summertime air.