Tropical Storm Season is Here, Is Your Green Roof Ready?

It is that time of year again.  Soon there may be cyclones in the Atlantic, wave after tropical wave forming off the African continent and storming westward across the Atlantic.

If your green roof has a parapet then you are lucky.  Most testing has shown parapets minimize wind damage to a green roof - though in a large hurricane, all bets are off.

Even if your green roof does not have a parapet it can still be designed to minimize tropical storm wind damage.

The video here is of a small green roof in Jacksonville, Florida on August 25th, 2008 when Tropical Storm Fay pummeled the northeast Florida area with over twenty inches of rain.  The video shows how the roof reacted to gusts up to 50 mph.  Wind speed was recorded using an ExTech anemometer.

The roof shown in the video does not have a parapet and is sloped.  The video illustrates how the irregular surface of he vegetated roof interrupts wind generated uplift that can damage asphalt shingle roofs.  The plants range in height from two inches to six inches and can be seen moving back and forth in response to the wind.

Wind racing across a flat surface can create lift - or a vacuum - and literally lift the shingles or roll roofing up off the decking below.

The plant habit acts to break the shear flow of air, creating turbulence and working against damaging uplift.  Planting more wind tolerant plants, such as some succulents or grasses may actually create wind breaks in a manner similar to the way a parapet would act.

Another important quality of a well designed green roof is the drainage factor.  The roof here is allowing a rapid drain of roughly 18" of rain over a 24 hour period without washing out. 

Monolithic hurricane mats used as the basis of the planting system allow for quick drainage of the stormwater and create a mechanism where plant roots can attached and anchor themselves to the roof all the while holding soil in place.  A well established root architecture  is important  for tropical green roofs subject to high winds and heavy downpours.

We will always deal with the 5 H's here in Florida - High Heat, High Humidity, Hard Frosts, Hurricanes and Hard Desiccating Winds, but with good green roof design your Florida Green Roof can hopefully withstand a severe storm, including tropical storms!

In the meantime, there are some precautions the green roof owner can take to prepare for tropical storm season (May 15th for the Pacific area and June 1 for the Atlantic regions).

At a minimum, we recommend;

1. No large trees on a roof.
1. Small shrubs and small trees may be used successfully depending upon the final design.  This may seem like a common-sense guideline but people try to put all types of tall, large trees on patio or garden roofs.  During a 130 mph cyclone, the tree may be blown over and may cause damage from the fall against the structure or to the street below.  It may also become airborne if the winds are strong enough.  Growing up in Hialeah I saw plenty of hurricanes come through our area and witnessed first hand the power of these storm events.
2. Anything and everything on a roof should be permanently attached.  
1. Walkways should be constructed from a permanently attached TPO, EDPM or other mat and permanently affixed to the roof.
2. No loose chairs, tables or other items should be present.  If you wish to have a chair and table stay on a roof during a cyclone, they must be permanently attached.
3. All green roof components must be permanently attached to the structure.
4. Any trays, plastics, pots, containers or other green roof components must be permanently attached to the building structure.  Florida Building Code does not allow for loose items to be installed on a roof - they must be attached.
5. Green Roof Irrigation components must be permanently attached to the roof.
3. Make sure all tools and gardening utensils are picked up and put away.
1. It is very easy to forget the pair of shears, scissors or pliers on a roof.  Remember what you were using and where you liad them.
4. Plant selection should be focused on those species that have historically survived cyclone and hurricane incidents.  There are several good books available at most bookstores here in Florida on proper cyclone resistent landscaping and many resources on the web, such as the Brevard County Landscaping Guide for Hurricane Areas.
5. Check on the NOAA National Hurricane Center website daily.  The NHC webpage is a wonderful resource, full of links to climatic data.

Always use a green roof design or green roof system already proven in actual field trials with hurricane simulation testing.  Watching a green roof blow off during a storm is an avoidable event.  Due diligence upfront and preparedness is important for green roofs in hurricane prone and cyclone impacted areas.

Florida Green Roofs and Hurricanes, Storm Season is Fast Approaching

The Eastern Pacific Hurricane season begins soon and the Atlantic Hurricane season follows shortly thereafter.

Routine green roof maintenance and hurricane inspections are important for Florida Green Roofs

Hurricane design is an important consideration for green roofs.  If a green roof is to be built in areas subject to hurricane or cyclone impacts then a few simple guidelines will help make the design more resilient against wind and storm damage.

At a minimum, we recommend;

1. No large trees on a roof.
1. Small shrubs and small trees may be used successfully depending upon the final design.  This may seem like a common-sense guideline but people try to put all types of tall, large trees on patio or garden roofs.  During a 130 mph cyclone, the tree may be blown over and may cause damage from the fall against the structure or to the street below.  It may also become airborne if the winds are strong enough.  Growing up in Hialeah I saw plenty of hurricanes come through our area and witnessed first hand the power of these storm events.
2. Anything and everything on a roof should be permanently attached.  
1. Walkways should be constructed from a permanently attached TPO, EDPM or other mat and permanently affixed to the roof.
2. No loose chairs, tables or other items should be present.  If you wish to have a chair and table stay on a roof during a cyclone, they must be permanently attached.
3. All green roof components must be permanently attached to the structure.
4. Any trays, plastics, pots, containers or other green roof components must be permanently attached to the building structure.  Florida Building Code does not allow for loose items to be installed on a roof - they must be attached.
5. Green Roof Irrigation components must be permanently attached to the roof.
3. Make sure all tools and gardening utensils are picked up and put away.
1. It is very easy to forget the pair of shears, scissors or pliers on a roof.  Remember what you were using and where you liad them.
4. Plant selection should be focused on those species that have historically survived cyclone and hurricane incidents.  There are several good books available at most bookstores here in Florida on proper cyclone resistent landscaping and many resources on the web, such as the Brevard County Landscaping Guide for Hurricane Areas.
5. Check on the NOAA National Hurricane Center website daily.  The NHC webpage is a wonderful resource, full of links to climatic data.

Always use a green roof design or green roof system already proven in actual field trials with hurricane simulation testing.  Watching a green roof blow off during a storm is an avoidable event.  Due diligence upfront and preparedness is important for green roofs in hurricane prone and cyclone impacted areas.

Green Roof Plant Sleuthing! Understanding why some plants grow better on roofs.

I call the process - 'Green Roof Plant Sleuthing'!

Simply put, Mother Nature is the best teacher for what grows well on a wall or on a roof in hot, dry, arid and monsoon-like climates.

Nature created green roofs cool buildings and provide habitat

When students of Green Roof technology ask me for recommendations concerning plants and green roofs, the first task I suggest is always to do a little Urban Sleuthing.  Walk around downtown, watching your step and keeping an eye out for traffic yet looking up to the city roofs, gutters and tops  of building structures.

Most are amazed to see just how many plants actually grow out of cracks, with minimal soil and survive the typical harsh conditions of a rooftop.

Green Roof Sleuthing is fun & educational!

Excitingly, these naturalized plants can produce a full and flush growth habit, offering an almost tropical look to the roof.

Walking through St. Augustine the other day I ran across many nature inspired green roofs, all quite beautiful and providing habitat, cleaning stormwater, cooling the buildings and pumping fresh oxygen back into the air.

Hidden among the lush resurrection fern were also many interesting smaller ferns, vines and other plant species.

MetroVerde finds many new Green Roof Plants through Florida Green Roof Sleuthing

So next time you wonder about the type of plants to use on your next green roof project, be sure to consult with your local nurseries and growers but also do not forget to do some Green Roof sleuthing yourself.   Take a walk through the downtown and look up.

Chances are you may never use those plants you see growing out of the buildings but then again, knowledge is power, especially when working with plants on roofs!

Ethnobotany for Green Roofs, Achillea millefolium, Yarrow on Florida Green Roofs

Rooftop ethnobotany should be a part of all green and living roofs as plants have given humans food, fiber and medicine throughout the ages.


One of my favorite green roof plants rich in ethnobotanical history is Yarrow.

Green Roof Achillea millefolium, ethnobotanical wonder and living roof beauty

Yarrow is a hardy Northern Hemisphere native wildflower suited for hot, dry green roofs. Yarrow is found growing as a native plant around the world in the northern hemisphere. 

Her Mexican name is plumajilla or ‘little feather’ due to the feathery shape of her leaf.
Important to biodiversity support, many birds (including sparrows) use the soft leaves of the plant to line their nest.  The leaves are quite soft and add a blanket of light green color across the green roof for much of the spring and early summer.  When the blooms began to appear during late May and June the plant sends up shoots, supporting beautiful umbells of flowers. 

Green Roof Achillea millefolium, Breaking Ground Green Roof

Yarrow has a rich ethnobotanical history having been used for centuries as a wound herb, and is famous for the capability to stop bleeding from cuts. The leaves may be used as a spinach like vegetable, cooked or in salads.  The plants has also been used as a flavoring in beer. Yarrow has EO data suggestion insecticidal qualities against common mosquitoes.

MetroVerde Green Roofs supporting biodiversity on many levels, Yarrow

Yarrow can tolerate hot, dry soils with little organic material.  A member of the Asteraceae family the plant is very drought tolerant once established. The flowers add a variety of surprisingly bright color to the green roof as many other flowering plants are seeding out and loosing their color.  The perennial plant usually comes back and flowers reliably, year after year.

During the harvest season when most green roof plants are beginning to wear a tired look from summer's heat and humidity, Yarrow is just beginning to develop a rich, deep rainforest-like green hue.

Shown growing here with Pennywort, Hydrocotyle spp. and Aloe, Yarrow serves as a weed blocking  groundcover worthy of any living roof.

Green Roof Photos for a Florida Friday Morning

Green Roof plants seem to love the respite from the harsh summer temperatures.  Check out these flowering beauties.

Green Roof Roselle bloom, Hibiscus sabdariffa, tea & ethnobotanical plant

Florida Green Roof calabasa

Early morning Florida Green Roof cosmos

Green roof early morning pink muhly native grasses

Green roof early morning pink muhly native grasses

Green Roofs and Healthy Buildings

Typical air we breathe contains about 20% oxygen gas under most conditions.  A stale, stuffy building may contain only 17 to 18%, levels far too low for optimal body health and brain performance.

Plant leaves clean the air and supply oxygen!

Yet oxygen levels in the rainforests can reach up to 24% of the ambient air!  We all know how refreshing it is to walk through the forest.

Plants produce oxygen during the photosynthetic process where carbon dioxide and water are changed into sugar and oxygen.  The sugar is used by the plant to grow and the oxygen pumped back into the air for us to breathe.

Air Intake over Green Roof!

One way green roofs can help create healthy buildings is through oxygen production around air intake vents in the Air Handling systems.

As the fresh air intake opens, the invisible cloud of high percentage oxygenated air enters the building, replacing stale CO2 with fresh, pure O2.

Increasing the building O2 content just slightly can have significant impacts on occupant health, attitude and productivity.

Green roofs for healthy buildings!

Green Roof Growth Comparisons, Six Months on a Florida Green Roof

When we created the Breaking Ground Green Roof our intent was to implement a nature irrigation based food and native plant roof providing economic benefits as well as environmental impact.

Today's post shows how much the roof has grown over the past five months.

April 2011, BGC Green Roof by MetroVerde

The roof system is designed to be hurricane resilient and convert atmospheric gas into usable forms of nutrients by the legumes and their associated nodule bacteria.

Air conditioning condensate is captured and distributed within the system.

We are still classified as an area under severe drought by USDA's Drought Monitor.

Today the Green Roof is a living example of just how much food, flowers and habitat a rooftop can produce.

August 2011 BGC Green Roof Jacksonville

Following basic permaculture principles with an emphasis on wind and light exposure forms the foundation for this projects growth.  Many of the plants are evergreen perennials and we expect the roof to continue preforming over the long term.  For more information on the project, visit the MetroVerde Website and then be sure to visit the Breaking Ground Green Roof project website here.

Green Roof Plants and Root Barriers - Root Tips and Seams

Today's technical insight focuses around the situation of plants having agressive root growth habit near waterproofing or root barrier membranes.

Sometimes the membrane installation will have a seam just in the place you wish it did not have a seam.

Seams and seam welds are normally designed to hold up against stormwater and normal use but an agressive root tip can quickly and easily penetrate the welded area between two layers of barrier membrane and create a leak.

Green Roof Membrane Seam and Plant Placement

Yet seams are usually very strong.  Think of water supply pipe and the glue used to attach both pieces - the resulting bond is permanent enough to prevent pressurized water from leaking out of the pipe and the same holds true for a properly welded waterproofing or root barrier membrane.

But some roots have a way of exploiting even the smallest cavity along a seam, finding their way through the bond and creating an eventual issue.

An easy way to circumvent a potential problem is to try and plant or place the green roof plants on the side of the top membrane layer.

Root architecture studies on most green roof plants show a growth pattern radiating away from the center of the central stem.

By placing the plant on the upper membrane layer the roots will generally have a tendency to grow over and down and away from the exposed seam edge.

However by placing the plant on the side of the membrane seam having the lower layer, the roots naturally grow directly towards the exposed membrane seam edge.  This placement creates a distinct disadvantage and potentially allows for outward expanding root tips to find voids or cavities in the membrane seams.

Importantly, not every green roof plants will have well behaved roots that grow outwardly.  Some species, like bamboo and other plants have roots that grow in all directions and will seek out seemingly all potential cracks and seams.

So the planting tip included here is not a solution to green roof plant problems, it is a precautionary measure, one that should be implemented whenever possible.

If your membrane is seamless you don't have to worry as much.  But many roofs have seams as well as many membranes, both root barrier and waterproofing.

Know your seams.  Find them visually the first time ou walk on a roof of a potential green roof project. Keep their locations in mind and on your design sketches and drawings.  Then properly place plants to avoid seam root tip intrusion.

Cradle to Cradle Biodiversity, Green Roofs, Rooftop Permaculture

Cradle to Cradle is a popular term in Green Building circles, encompassing the concept of recycling, reuse and elimination of unnecessary waste.  Many times though, the 'Cradle to Cradle' concept is forgotten about and simply over-looked with respect to site landscaping.  Although certainly an integral part of any site development or redevelopment project, landscaping is typically not considered a part of a building and as such is often ignored when building sustainability is discussed.

Biodiversity efforts include saving existing plant material

The other day I received an email from Catherine Burkee, Breaking Ground Contracting's Education Director discussing the green roof component of the project.  Catherine used the term 'plant rescue' in a conversation about site biodiversity preservation and the living walls and green roof.  A portion of the BGC green roof project would serve to house a representative sample of the existing flora on the site, affording the site's original plant genetic material an opportunity to continue growing, existing into the future rather than being destroyed during new landscape preparations.

The continuance and preservation of original site biodiversity may be more critical than most first think.  The most humble appearing plant may provide a critical function to the health of our world.  The Breaking Ground green roof project looks to greatly improve site biodiversity, encouraging all plants - food, native wildflowers and Florida friendly landscaping plants, an opportunity to thrive.  Importantly the team has recognized the ecological value of existing plants.  Through plant harvesting and replanting on the green roof, the area wildlife (insects and other pollinators) will not be loosing specific plant types they have come to expect and be dependent on across the lot.



Recall the small Taraxacum plant and the honey bee post of last week.  The specific plant mentioned in the post was harvested and replanted for use in the green roof.  Ideally, site plant material should be harvested for preservation during the dormant season or during a rainy period to reduce plant stress.

Jacksonville has received the first significant rainfall of 2011 this past week and the soil was wet from the precipitation.  Site plant's vascular systems were saturated with water and photosynthesis processes going strong when we went to the site to collect the specimens to be relocated.

Collections were made of all the herbaceous plants we identified during our site bio-assessment plus an additional  eight species.  Specimens were dug using a shovel, tagged and placed into a bag for transport tot he nursery.  Once in then nursery they were potted up into shallow containers to acclimate them to green roof living.

Certainly the plants collected are considered by many to be simply 'weeds', not readily available for purchase at the local nursery or even native plant nurseries.  Many are those plants who are routinely saturated with herbicides and other poisons because they do not fit the definition of a culturally accepted landscape plant.

Yet if we are to take cradle to cradle concepts seriously we must look at our site's existing plants with new perspective.

Benefits of site plant material preservation and adaptation into a small section of the green roof are many.  The overall number of site species will be increased.  Native seed source will be preserved.  Nectar and pollen sources will remain and supplement those additional and new nectar sources brought to the site with the new green roof, living wall and landscape plants.

Biodiversity increases exponentially with increased plant diversity.

In keeping with the 'Cradle to Cradle' sustainability model, the Breaking Ground Project incorporates a continuance of native plant genetic material into the building's living roof.  True sustainability looks beyond just the building structure.   Harvesting site flora for reuse and 'plant rescue' is an excellent example of comprehensive 'Cradle to Cradle' sustainability put to action.

Green Roof Plants - Root Architecture - Nitrogen Uptake

The SimRoot root architecture 3D model is fascinating and informative.

Though the analysis results are common sense, seeing available nitrogen removed from the uppermost soil levels is important to the capabilities of green roof plants and their capability to clean stormwater.

Watch the following youtube video of SimRoot from Penn State.

You will see the time lapse simulation of the root growth and note the concentrations of available nitrogen decreasing rapidly in the surface area.

More soon!

Happy Green Roofing - Kevin

Green Roof Images and Photos from the Green Roof Blog and Resource Center

Green Roof Cross Section - Extensive, Non-Irrigated Exhibit

Attached is a cross section of a Florida Extensive Green Roof - non-irrigated, installed over asphalt shingles on a 5/12 sloped roof.

Green Roof Cross Section - MetroVerde Extensive

We will be uploading our reference library of exhibits and cross-sections to the blog here over the next couple of months.

Click here for the PDF file version ( a little higher resolution) of the MetroVerde Florida Extensive Green Roof Cross Section exhibit.

Happy Green Roofing!

Kevin

Did your Green Roof Turn Out To Be Something You Didn't Expect?

Don't laugh just yet - I hear this comment often!  And its true, vegetated roofs have a mind of their own.  But today I am writing because I was meeting with one of the professors at one of the universities last week.  We were discussing a stormwater research project.  Near the end of the meeting the conversation turned to the many BMPs referred to in the proposed new Florida stormwater rule, one being Green Roofs.

The professor, with humor in his/her voice, spoke of the green roof project the university architect designed and how after installation the roof looked beautiful.

Continuing, the professor added that the roof had changed so much over the past year that most associated with the project were shocked.

I've seen this occur on every vegetated roof here in the Southeast US.  The maxim is:  Unless you have an endless budget for maintenance and unlimited time to work with the roof, expect change.

Through design you can minimize the change but you should still expect change.

The winds, rain and birds bring seed material.  New aggressive pioneer species pop up right and left.  The harsh environment knocks back the carefully tended to plants installed during the initial planting.  Harsh winds desiccate some of the plants.   Others wilt or develop dampening off with the high heat and humidity.  A vegetated roof generally has a mind of its own and you must ask if you have the time and energy to fight.

Again, I remind all I am speaking from a Florida and humid Southeastern US perspective.  Green roofs may behave different up north, I do not know.

So, I smile when I hear someone say, usually while shaking their head, that a vegetated roof has turned into something they did not expect.

We are compiling a database of plants suited for Southeastern US roofs and will be posting before the end of the year - would love your feedback.

Happy Green Roofing!

Kevin