Thermal Fluxes in Recycled Versus Conventional Green Roof Media
Open Access
- Author:
- Widjaja, Angeline
- Area of Honors:
- Mechanical Engineering
- Degree:
- Bachelor of Science
- Document Type:
- Thesis
- Thesis Supervisors:
- Dr. Shirley Elizabeth Clark, Thesis Supervisor
Oranee Tawatnuntachai, Thesis Honors Advisor
Katherine H Baker, Faculty Reader - Keywords:
- green roof
green roof media
heat flux
thermal analysis
enviromental
shale
crumb rubber
urban heat island effect - Abstract:
- Green roofs, consisting of plants and a growing medium, are an old technology that has been recently adapted for modern use. These roofs offer a sustainable alternative to conventional roofs, and provide environmental, health and aesthetic benefits. This study analyzed the effects of moisture and winter/summer conditions on heat flow in both recycled crumb-rubber/compost and commercial (expanded shale/peat) green roof media. A 2^3 factorial experiment was conducted on laboratory-scale, unplanted green roofs. Heat lamps were used to simulate sunlight and the lighting was timed for either average summer or winter daylight hours with the lights off for the rest of the 24-hour period. The moisture level comparison used was either saturated with no drainage from the media or free drainage. Comparing the media, the results showed that the crumb-rubber media retained more heat irrespective of saturation or lighting conditions and therefore may be better suited to colder climates which require consistent insulation. In contrast, the behavior of commercial media varied more with saturation levels than with lighting. As moisture levels changed, the temperature gradient reversed. When saturated, the commercial media surface (half-depth) was cooler than the bottom layer, and in unsaturated, free-draining media, the bottom was cooler than the top. Statistical analysis using a 3-Way Analysis of Variance (Factors: Media, Moisture, and Temperature) showed that, as observed, the only factor that was significant was the media composition at both full and half-depths in the media. For moisture, saturation level at the start was only significant for the full-depth probe. Media composition and temperature was not significant at either probe depth. This likely is due to the fact that the drainage holes for the media were plugged to achieve saturation and the temperature of the recycled media, while hotter than the commercial, was not hot enough to cause excess evaporation from the recycled media. These results can provide insight for producing more efficient green roofs, which may address the problem of Urban Island Heat Effect (UHI), a phenomenon created by the existence of heat retaining structures around urban areas.