By Kevin Songer, J.D., LEED AP, Tropical Green Roof Editor Tropical Green Roofs Column 7/16/14
Photos and Graphics by Kevin Songer Unless Otherwise Noted.
Welcome to Part Two of our series entitled "Design Model for Coastal Green Roofs." Although the title says "Coastal Green Roofs" and we are focusing in on a beachfront green roof design, this series of posts is applicable for use in the design of most any green roof.
B. Collecting and compiling background climate and other biophysical data.
We also talked about green roofs in terms of being a self-sustaining ecosystem and suggested the notion of complex "types, forms and interactions" perfectly describing what successful living roofs become. These types, forms and interactions comprise the design variables we will examine herein and try to better understand as we develop the components of a nature irrigated green roof. Our goal here is documenting how our roof variables behave and you being able to predict how the green roof plants will grow.
For this series of posts our client is an architect, one who has incorporated green roofs into her projects before. She also possesses an appreciation of nature and desires her beachfront home to "become part of the existing dune system, blending in to where the structure looked as though it sprang up out of the dunes naturally." Her living roof will be three stories up in the air and even though the green roof assembly would not be visual from the ground or adjoining structures, the owner would enjoy many other benefits such as habitat creation for shorebirds, stormwater attenuation and cleaning, green house gas mitigation, carbon sequestration, urban heat island effect reduction and lots more.
Native plant species Gaillardia pulchella, Blanketflower, Glandularia maritima, Coastal Vervain, and Serenoa repens, Saw Palmetto, cover the site slated for construction and a green roof.
First, with the mission statement "Our green roof will help weave our home into the existing self-sustaining dune ecosystem complimenting and supporting the many existing complex ecological and biophysical functions on the site" in hand, we now possess an important cornerstone for proceeding with design.
I always ask a prospective client the question, "Why do you want a green roof?" sometime during one of the first face to face meetings we hold. Many times the client hesitates, not really knowing why they want a green roof. Undoubtedly the most common answer I hear is, "Because it will save me money on heating and cooling, you know."
Yes, a green roof will moderate temperature swings on a roof, leveling heat spikes on hot afternoons. But many factors contribute to utility bills, not just green roof performance and one way to ensure a happy client is to clearly define expectations from the start. Sometimes at first the client can’t really put their finger on the reason why they want a green roof - they just know they want one. Other times the client knows exactly why they want a green roof.
As clearly memorialized in her green roof mission statement, our client wants her home to blend into the dune. One approach to accomplishing this is to use forms and plants already common to the site across the walls and roof of the structure. Although I am comfortable here in the Sunshine State with using either native plant species or popular water-friendly plants such as the University of Florida’s recommended Florida Friendly landscape plants, for this design I would look closely at the existing site vegetation for green roof plant candidates in light of the client’s pointed mission statement.
Beachfront and dune ecosystems are quite complex, supporting a host of plants and wildlife. Learning from existing dune patterns affords an advantage to the green roof designer.
Secondly, our climate data collection efforts have been ongoing now for several months. We are collecting lots of info about light exposure (remember PAR?), wind, temperatures and other inputs we will consider as primary and secondary design variables.
As we mentioned in the previous post, the development of a site pre-condition site model and subsequent modeling pre versus post requires collection of empirical data such as:
• Monthly wind speed and direction, • Daily temperature graphs - low, high and mean, • Seasonal air water vapor & humidity characteristics, • Monthly rainfall amounts, daily trends, • Sun exposure, shade amounts, • Adjacent and indirect impact factors, • Existing plant types, • and much more as we shall discuss.
We are going to continue assembling pre-condition site weather and climatical data over the next several months. I will particularly be interested in the hot summer wind speeds, humidity levels and PAR (light).
Site biophysical background data collection involves learning about weather conditions and existing plant communities characteristic of the site.
Returning to the client’s mission statement, let's look at a couple valid approaches to fulfilling her green roof wishes. The client here wants the green roof to function as an architectural component purposed with the mission of making the home blend into the dune. A designer could move forward with several approaches, including:
A. Choosing a water-friendly landscape or green roof plants proven to work well in a similar environment;
B. Selecting native species presently growing across the site;
C. Selecting plants that may look similar to those native species growing on the site and have proven themselves on similar green roof applications;
D. Or other approaches.
Species thriving across the dunes offer insights into what plant survival mechanisms may be necessary to succeed on a coastal green roof.
This is where the green roof designer’s choices should be grounded in experience, intuition, and expectations, based upon good horticultural and ecological systems science. Because the ultimate responsibility for the green roof’s performance will lie on the shoulders of the designer, he or she must have the flexibility to specify those plants they feel best meet the intent of the mission statement on a long term, sustainable basis and in accordance with a host of other structural, cost, safety and maintenance principles.
In my opinion, a plant is a plant (excluding highly invasive, illegal or otherwise prohibited species) and any green leafy life growing up walls or across a rooftop brings myriads of benefits, native species or not. Now, I also personally believe there are many benefits to using native plant species on a roof, too, and we should strive to support that which Mother Nature has shown to be successful through vast expanses of time and natural selection. I take to heart the lessons I can learn from nature.
Documenting plant bloom patterns helps the green roof designer meet client intent and mission statement requirements.
As an aortic dissection survivor I am faced with the daily challenges of supporting the health of my heart and cardiovascular system all the while doing this on a low-impact basis physically. Daily walks throughout our local parks, beaches and downtown areas provide just the right amount of conditioning without stressing my paper-thin aorta wall. I always carry my camera (lately the IPhone has taken the place of the SLR) and document most all plants in bloom or those presenting in an interesting manner, filing the photos away in cloud folders sorted by ecosystem types. So, while I am walking to stay alive I am also learning a great deal about plant habit, information that ultimately assists me in developing a successful green roof design.
In my own words, the client’s mission statement says "Kevin, design a green roof that helps my house blend in with the site." Although each designer’s approach will be different, I plan to use plant types that either grow naturally across the site or plants similar in appearance to those site native species. Ultimately, since the roof will not be seen except during periodic maintenance checks, from an airplane or by pelicans, the final plant community will be a vision in the client’s mind. Still, I intend for the roof to fulfill the mission statement's intent.
At first glance the coastal dune construction site may appear to support little wildlife diversity and grow only sand spurs or sea oats. But this assumption may just be a direct reflection of our unfamiliarity with the site’s existing ecosystem. Even the more sparsely populated natural ecosystem is usually quite complex. Understanding this complexity - the types, forms and interactions we mentioned above takes time and really involves getting to know the site. To better understand this complexity we use a tool called a "Bloom Rose."
Seasons of a Coastal Green Roof: Bloom Rose development for green roof design assists in developing an understanding of site existing ecology.
When designing a Green Roof one of our project objectives almost always includes not only survivability and "green" but also year round color or bloom interest. Of course, the presence of leaves and flowers are also dependent on the level of winter's harshness. But knowledge of color predictability is an important component of green roof plant design.
The Bloom Rose process helps us forecast color, texture and hue. On this coastal project, the Bloom Rose will help us design a green roof that frames the house as a "dune integrated structure." Moreover, while assimilating the Bloom Rose data, we will learn much about what plants may be available for our ultimate green roof planting design.
The Bloom Rose creation process takes existing site biodiversity data and then visually summarizes potential green roof colors, textures and hues over an annual cycle.
It doesn’t matter if your project is along the beach, out in the country or in the middle of downtown Metropolis. Development of a bloom rose will tell the designer so much about a site. For example, on a previous urban green roof where at first glance there was nothing growing but mold on the concrete block walls, we ended up documenting many different plant species. Some of these supported local bee colonies and were transplanted up to the roof during the construction process and they or their descendants are still alive years afterwards.
Yes, there are many governmental funded seasonal bloom calendars available for the designer who may be pressed for time and can not go through the systematic approach generally required to develop a Bloom Rose. Once completed however, the Bloom Rose developed from multiple field visits over time exponentially increases the survivability chances of a green roof installation.
Though considerable time and effort may be involved in the collection of raw data required to develop an accurate Bloom Rose, it is highly recommended this step be completed as a preliminary process to discussing plant options with the green roof owner/client.
Seasons of a Coastal Green Roof: Summer & Fall.
Typically, this is how I recommend collecting field data for the development of a Bloom Rose:
1. Conduct three observatory walks, each week for an entire year across your proposed project site. Always carry camera journal and pencil. NOTE: In the event that time or budget does not allow for a year's data collection then there are a couple alternative approaches including:
1a. Work with a local botanist who is familiar with the surrounding site ecosystem, habitat and biota to establish a Bloom Rose based upon other verified records (there are some really great green roof plant nurseries and green roof botanists around the world who can also help you construct a Bloom Rose),
1b. Conduct site reconnaissance walks for as much time as is possible. Green roof construction usually is one of the last items to be installed on a project, usually allowing plenty of time for examining the different seasonal changes in the local botanical composition. Supplement the undocumented portion of the Bloom Rose with information from 1a above.
2. Identify every blooming plant you come across on each site reconnaissance excursion. Record when blooming starts, how long the bloom persists and when blooming ends.
3. Identify grasses, ground covers and shrubs, both native species and non-native species. Make notations as to whether the plants are evergreen, deciduous, perennial or annual.
4. Record as much secondary information about the site as possible, including hydrologic, climatic, wind, light and land use.
5. Visualizing an annual cycle as a circle, create a Bloom Rose with crayons, colored pencils, graph or drawing paper or with a computer drawing program. Include common names and scientific names. Use the text color that best matches the actual bloom color of the plant you are describing. Be sure to align the name of the plant in the circle section representing the season of the year the blooms occur.
Seasons of a Coastal Green Roof: Winter & Spring.
Appropriate green roof plant selections will support long term success on your living roof project. Although plants are unique living organisms and are each inherently different just like each human is different, you can still predict long term viability with increased confidence over an off-the cuff or random plant selection processes.
Look to the Bloom Rose as a summary of what Mother Nature has fine tuned over epoch time intervals. The native plant purist side of me pushes my design towards site specific plant species. However, the artist and explorer side of my designer efforts lead me to read the Bloom Rose more broadly. Not only do I see individual species within the Bloom Rose thriving across the site and future rooftop, but I also see Genera and plant Families, Subtribes and Tribes of potential green roof plants.
So your Bloom Rose will not only point you to individual plants but it will also teach you about other similar plants in the same Genus or plant Family. Many plant survival mechanisms that may be well suited for your project site can be found in other plants within the same botanical groupings, yet perhaps more readily available on a commercial basis. I look at the Bloom Rose as a way of codifying what Mother Nature’s successes into a visual object that is easy for me to look at, comprehend and understand all the while telling me more about what plants will survive on a green roof than many textbooks.
Whichever approach you take as a designer, equipping yourself with as much understanding of what plants grow best across your site will pay off with long term green roof success. Finally, think of the Bloom Rose as a tool that takes you, the designer, beyond blooms. Think of the Bloom Rose as an exercise in design due diligence - one of arranging plant selection around a logical approach, one based in the science of existing botanical successes across the site.
Endemic evergreen groundcover, Coastal Mock Vervain, Glandularia maritime, is a salt and drought tolerant species discovered growing across the site and a potential green roof candidate.
Now that we have developed a mission statement, bought into wholeheartedly by the client, and have developed a good idea what plants have successfully evolved over eons of time to survive in ecosystems like our project’s site, we are well on our way to starting a good green roof design. With these two insights to direct our efforts, the ultimate goal of a successful green roof becomes realistically much more achievable.
With the "bio" component of our "bio-physical" variables documented we will next will turn to the climate, weather and "physical" variables we have been collecting data about. Next post we will begin integrating this climatic data into our model approach and the green roof design will become to take on real form. Our green roof vision will have moved from the vague to a very real vision, one now with significant substance, ready to begin taking shape.
We will leave you with a few photos of the recently completed tropical green roof atop the new Starbucks store on Main Street, Disney Orlando – an exciting example of cradle to cradle sustainability.
Kevin Songer, J.D., LEED AP, is our Tropical Green Roof Editor (March, 2012). Kevin serves as tropical, coastal and hurricane green roof expert for MetroVerde, a Florida based vertical green design company. He was awarded the 2012 City of Jacksonville's Environmental Protection Board's Christi P. Veleta Award, 2011 'Green Hero' of the year award, and the 2009 Innovation in Landscape and Water Conservation recognition by the Northeast Florida Chapter of the USGBC. Kevin has spoken of the economic and ecological benefits associated with green roofs at numerous functions and seminars. Watch his "Coastal Green Roof Design and Native Plants" video from our Greenroofs & Walls of the World™ Virtual Summit 2013. And he served on Greenroofs.com’s "Wind. Water. Heat. Grow. Greenroofs."Panel Session with Dr. Bill Retzlaff, David Aponte, and Joe Webb during the 2011 Greenroofs & Walls of the World™ Virtual Summit.
Kevin writes a daily green roof blog, Living Green Roofs, is presently designing several oceanfront green roofs, just completed design work on the first Green Roof in Bermuda, is an Aortic Dissection survivor, and contributes green roof notes to the Native Plant and Wildlife Garden web project. Kevin also holds an undergraduate degree in biology and the Juris Doctor degree from Florida Coastal School of Law with a focus in environmental law.
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