Jumpstarting Green Roofs in Florida

I am fascinated by green roofs because I think they have unlimited potential to look really cool (usually my first attraction) but also because green roofs have amazing benefits that help the world, in general, and South Florida, in particular. It’s a “no brainer” that here, where it is really hot, we could benefit from reduced air conditioning needs, protection for roof membranes from the blistering heat, reduction in urban heat islands and help with storm water management.

Green roofs have made a minimal foray into Florida, with a dismal effort in South Florida. To date, there is a green roof at University of Central Florida that was installed about three years ago. A comparison between an area of conventional roof and an area of green roof done by University of Central Florida’s Stormwater Management Academy was published in the February 2006 ASHRAE Journal. The research showed that the daytime temperature for the green roof was 39 degrees cooler than the conventional roof! The ‘conventional roof’ was highly reflective and the study was done before the plants were fully grown. The average energy use required to remove the additional heat gain from the conventional roof over the summer period that was monitored was approximately 700 Watt hours per day. If a darker roof and more fully grown green roof were compared the savings would have been even greater!

There is also a green roof at University of Florida, over unairconditioned space, and one in the Keys at Nancy Foster Nature Center. Recently, a green roof system that cleans grey water was installed at the Eco-Centre in Lake Worth, but it has not yet been planted.

To reap the many potential benefits, it is important to study specific South Florida conditions that are different from most of the nation. It gets really HOT down here in August and September. How much hotter does it get when you are 30’-40’ higher? Does the cooling effect of a green roof offset its cost? How quickly? It is really HUMID here – Sedums used on green roofs in the rest of the country just won’t work- they get fungus and melt. We have BIG STORMS here. One of the fears I hear over and over is, “Won’t that stuff blow off the roof?” We get a LOT OF RAIN in short periods of time. What size planters and what conveyances would work best to either hang on to that water, use it for another purpose or make sure it’s clean when it comes out? We have a LONG GROWING SEASON. What plants will work best in the long run, that won’t get root bound? Or, do we need to figure out a modular system that will withstand hurricane force winds and can be changed out as plants overgrow?

Each project will, of course, have different conditions and parameters that require different solutions. A baseline understanding of answers to these questions is imperative so that green roofs can succeed in giving the benefits that they have the potential to give.

A demonstration green roof could evaluate different methodologies and educate the public on the many benefits that green roofs could provide South Florida. Does anyone know of an agency contact that would be willing to sponsor or give a grant for these studies? South Florida Water Management? IFAS? FAU? Palm Beach Community College? Palm Beach Atlantic College? Florida Power and Light?

Meanwhile, Roy-Fisher Associates is setting off to tackle some of these questions. We began with a visit to the Nancy Foster Nature Center, the only installed green roof in South Florida. This green roof has the worst conditions South Florida can dish out. It is on the very tip of Key West- probably the hottest spot in South Florida. It is also on the ocean, exposed to salt winds and it survived Hurricane Wilma. An upcoming entry will talk about our visit. As other green roofs are planted, we will report on them.

We are also testing a light planting media and specific plants in trays on our roof. An upcoming entry will describe our research approach and methodology. We will be posting data and pictures of our progress . These are labeled as ‘green roof entry’ on the calendar if you would like to review our progress.

We also plan to review material presented in Living Architecture Monitor and compare/relate it to South Florida conditions. Your comments on these reviews will be greatly appreciated.

We invite our professional partners to become regular contributors to our green roof entries, supplementing our expertise on engineering, contracting, environmental and architectural methods to create a sustainable foundation for green roof culture.

Sprout!