extensive green roof

Green Roof Microclimate: Patch Seeding Native Prarie Plants

A suite of microclimate variables affected germination of five Great Plains native plants seeded on an extensive green roof. Germination was significantly (~' = 0.05) greater in a greenhouse control versus the green roof for shortbeak sedge and prairie spiderwort (Carex brevior (35% versus 23% Tradescantia occidentalis 19% versus 0%). No significant germination difference between the greenhouse and green roof existed for two, warm-season species, Liatris squarrosa and Eragrostis spectabilis. Significant differences in microclimatic conditions between green roof plot locations suggest a heterogeneous environment can decrease seed germination. This impact was attributed to differences in the receipt of solar radiant energy, surface temperature, and vapor pressure deficit. Light reflection and thermal emission from the adjacent buildings supplied additional energy in some locations (depending on time of year or time of day) that varied greatly over only a few meters. Designers must carefully analyze microclimate impacts and consider those implications for plant selection and seeding. Establishment of some native seeds in high temperature zones may take more irrigation or benefit from mulching than those in moderate temperature zones. Increased seeding rates and targeted seeding dates may also be useful strategies. Future green roof research should examine germination across steep microclimate gradients, seed a wider suite of native plants to broaden plant biodiversity, and follow seedling development and mortality.

Catalyzing Design-Science Feedback Loop in Green Roof Optimization for Hot Climates

Synthetic ecosystems such as rain gardens, green roofs, engineered wetlands and urban meadows are becoming increasingly popular for their intrinsic environmental and ecological benefits as well as for their aesthetic value. But, as in many emerging technologies, communication between the academic institutions generating basic and applied science and the design disciplines is not as efficient as it could be, and strengthening this link will improve the performance of these systems. The case study serves to illustrate the process of linking research, design and implementation. Scientific research, performed by the authors and found in the literature, is used to inform design, and design challenges are used to suggest avenues of research. The research itself is briefly outlined where appropriate, but the focus of this paper is the process of linking science and design in a feedback loop.

Life Cycle Cost Analysis of Extensive Green Roofs in Switzerland and the Netherlands

Extensive green roofs in Switzerland and the Netherlands are economically sustainable when considering the added energy savings, municipal incentives and storm water fee reductions. By combing surveys, interviews, and reviews of municipal regulations for fifteen projects the Life Cycle Cost (LCC) was calculated by discounting green roof cash flows over a 50 year time period to determine a Net Present Value (NPV). This research finds that an extensive green roof NPV in Switzerland costs 27% - 37% less than a conventional flat roof. Similarly in the Netherlands, the NPV of green roofs is determined to be 16% - 26% less than a conventional flat roof. Presented here is summary of the results and the explanation of local influences of municipal incentives.

Fertility Management for Tomato Production on an Extensive Green Roof

Green roofs offer an alternative growing space to provide fresh vegetable products to urban
markets. The soil component is an important aspect of efficient green roof production systems
and adequate fertility levels are often lacking in media that are required to maximize plant
growth. This research project evaluated four fertilizer treatments on „Bush Champion II‟ tomato
(Solanum lycopersicum) growth and yield in a 7.62 cm green roof production system: (1)
vermicompost tea, 2) Miracle-Gro fertilizer, 3) Organic Miracle-Gro fertilizer, and 4) no
fertilizer. Treatments were applied weekly and ripe tomato fruit was harvested from June to
August. Results indicated that Miracle-Gro® provided the highest total tomato fruit yield, which
was 30% and 50% more in 2011 and 2012, respectively, compared to the next highest treatment -
Organic Miracle-Gro®. Plant vigor, chlorophyll content, and tomato yields indicated that
tomatoes can be successfully grown in a 7.62 cm green roof medium when given adequate
fertilizer applications.