Green Roofs

Green roofs can improve living conditions for human and non-human residents, but there are few in Southern California. Good Earth Plants in San Diego provides an overview. Given the aridity of the climate here, and the fact that the biggest financial driver for GRs is water management (e.g. retention, storage, runoff), we were surprised to learn that San Diego has a limited history of green roofs and few guidelines and codes.

We admire San Francisco’s policy and strive to tap into something similar for our region. Whether local or statewide, we plan to help establish local ordinances or programs that support the widespread implementation of GR technology.

Granted, there are a few examples of GRs for high-rise buildings in the city that offer tenants more pleasant views, improved air quality, reduced noise, reduced electricity demand, and reduced urban heat island effect. Perhaps the major environmental benefits of GRs on flat-roofed commercial and residential buildings are overlooked. As explained by our friends in Vancouver, GRs contribute to community well-being at all levels.

Biosolar combines a vegetated roof with rooftop solar PV. The two function in symbiosis, with grass or plants creating a cool microclimate around the solar panels through evapotranspiration, and the vegetation is irrigated when condensation forms and drips from the panels. Solar PV systems work best at temperatures below 90 F and if temperatures exceed 110 F, the solar power output can decrease by 10% – 25%. The installation of low-power fans to provide forced convection, and using white, non-reflective cells also improves the efficiency of solar panels.