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Influence of construction and demolition (C&D) waste on green roof performance

University of British Columbia

Green roofs have been used as an environmentally friendly product for many centuries and considered as a sustainable construction practice. Green roofs are built with different layers and variable thicknesses depending on the roof type and/or weather conditions. Basic layers, from bottom to top, of green roof systems usually consists of a root barrier, drainage, filter, growing medium, and vegetation layer. Environmental and operational benefits of green roofs are many. Green roofs must be installed on existing structures to maximize their potential environmental benefits; however, their main disadvantages are cost and weight. New technology enabled the use of light materials such as: low density polyethylene and polypropylene (polymers) to promote their installation. Nevertheless, lifecycle analyses demonstrate that more sustainable products must replace current green roof materials. This research evaluates indoor air temperature, indoor vapor pressure, water quality, and water retention performance of green roofs built with construction and demolition (C&D) waste. Temperature, vapor pressure, water quality and storm water retention were assessed by comparing the rainwater retained in experimental C&D based green roofs with standard green roofs under the same environmental conditions. Results show that C&D waste, compared to plastics, improves water quality, indoor air temperature and vapor pressure performance; however it reduces the water retention performance. These findings confirm the environmental potential of green roofs. Benefits of installing C&D based green roofs to minimize the impact of construction industry in landfills are potentially enormous. The Net Present Value (NPV) per unit of area of a green roof was estimated by considering the social-cost benefits that green roofs generate over their lifecycle. The economic analysis demonstrated that green roofs are short-term investments in terms of net returns. In general, installing green roofs is a low risk investment. Furthermore, the probability of profits out of this technology is much higher than the potential financial losses. It is evident that the inclusion of social costs and benefits of green roofs improves their value. In addition, this study evaluates the influence of green roofs on the seismic response of frame structures. Results from the structural analysis proved that intensive and extensive green roofs do not affect the seismic performance of reinforced concrete frame structures.

Text

2012-08-16

Attribution-NonCommercial-ShareAlike 3.0 Unported

http://hdl.handle.net/2429/42952

Civil Engineering

University of British Columbia

UBCO

http://creativecommons.org/licenses/by-nc-sa/3.0/