SAFETY FIRST 4 GREEN ROOFS

Safety must be a part of your Green Roof. Please review the resources on this website's Safety First page before ever climbing the ladder up to the roof!

Friday, July 25, 2014

Florida Green Roofs - Know Thy Plants!

Florida summertime is hard on green roofs.  Not only are roofing membranes subject to intense weather challenges, green roof plants also are subject to intense biological and meteorological assaults.
Summer humidity may quickly kill Florida green roof succulents
We have posted notes about Black Rot fungus before here on this blog.  It never fails though that every summer persons will contact me asking why their succulents are turning brown, black or rotting.
Florida green roof succulents battle the Black Rot fungus every summer
The simple answer is to use Florida native plants (preferably evergreen species but a mix of deciduous plants will work too, depending on the green roof location in the state).  Here in Florida native green roof plants usually far outperform horticultural succulents.
Florida green roof succulents rarely become the dominant green roof plant and usually die out
Florida summers bring maximum humidity and maximum temperatures.  With daily afternoon rain showers most rooftops become pressure cookers, steaming green roof plants like vegetables in a hot wok.  If you do not intimately understand Florida roofs and how plants preform there (and this only comes from hands on learning, failures and successes are the best teachers) then your roof design may quickly end up devoid of plants as you stand there, helpless, watching the succulents literally dissolve in the heat and humidity and fungus attacks.

Tropical green roofs are a challenge.  We have listed some great green roof native plants here.

Know how your plants will perform in a pressure cooker before specifying them on a green roof here in Florida.

Wednesday, July 9, 2014

Why Florida Green Roofs Are So Environmentally Important

Here in Florida surface water can directly flow into the drinking aquifer below the ground in many places.  Here is a video of storm water flowing down into the ground through a karst connection to underground caverns after a recent rainfall event.
Cleaning rainfall runoff with green roofs and other urban greening projects before the stormwater reaches our drinking water supplies makes good sense.

Avoidance of pesticides, herbicides and lawn fertilizers and chemicals is good not only for our environment but also supports a cleaner and healthier place to live in.

Sunday, June 1, 2014

A Florida Green Roof that Failed Over and Over Again - Missed Opportunity

Green roofs in Florida must be designed for a very unique set of rooftop variables.  Time and time again I see marvelous, well designed growing systems that work most everywhere else in the U.S. fail in Florida.
The first failure.  Check out the sprinkler erosion patterns in the green roof soil media.
Beware.  A successful Florida green roof is usually based not on the growing system.  Successful Florida Green Roofs are all about the rooftop plant design.  Other than hurricane resiliency and wind uplift issues, the green roof growing system could be a simple vertical coquina stone wall and with the right plants, be green and beautiful year around.

Remnants of the sedum plants that once covered the roof.  More irrigation erosions visible in the soil media.
I do not understand why this concept is so hard to understand by some.  But hopefully we can all learn from these 'hard' lessons.

Sedums work great north of Atlanta generally speaking.  The black death fungus commonly known as Southern Blight, Sclerotium rolfsii, that is pervasively present here in the Sunshine State, apparently wiped out the entire rooftop planting in a matter of weeks.

During hot, wet summer months, Southern Blight will turn many succulents to mush.  Want to learn more about this 'ScleROTium'?  Read more here.

Here in Florida there are a few 'constants' in green roofing design.  The underlying roofing assembly should keep the building water tight.  The entire roofing assembly and green roof system should be fire rated.  Additionally, the roof and green roof growing system should be wind uplift and tropical storm resilient.

A coquina rock wall can satisfy most of these requirements.  What I am trying to say is that here in Florida green roof plants can grow in any growing system installed on a roof.

What matters most is the type of plants chosen and how they interact with primary and secondary design variables.

The 10,000 square foot, green roof system shown here was a installed on the Aloft Hotel in Jacksonville, Florida by a well known national roofing company with a marvelous green roof line of products.

It has failed and failed and failed and was finally removed.

After the first attempt, perennial peanut, Arachis glabrata, was tried as a rooftop cover.  This design too was a failure. 
Such a waste of a beautiful green roof system.

Note the perimeter dead zone on the roof soon after the second round of plants were installed on the roof.  Within a short time the perennial peanut took off, but so did the Bidens app, Goldenrod, Dog-fennel, Ragweed, Pokeberry and extremely tall 'weeds'.

Hoses were draped over the edge of the roof to supply lots of water to plants destined to failure from day one.

Whirly bird sprinklers were set up on the roof but in the end did not save the plants, rather they contributed to washing out the soil media and atomizing-spraying what smelled like reclaimed irrigation water all over the swimming pool and garden patio area below.
Florida has the deadly seven H's.  Plants must be designed around each of them.

Hot summer, relentless photoactive radiation and no matter how much irrigation was applied the chosen plants dried up and turned brown.
This roof not only failed multiple times but also presented a serious liability and safety issue.  With rooftop temperatures approaching 150 degrees F, an afternoon breeze laden with a single cigar ash could have turned the entire structure into a great big torch.
Sometimes a green roof designer will mistake 50 inch annual rainfall amounts for being spread evenly over  four seasons.  Here in Florida it is not uncommon to see ten, twelve or sixteen week droughts without a single drop of rain.  
Again, the roof and growing system here are first class.  But in Florida, a successful green roof is designed around the plants.

I recommend talking to a nursery specializing in green roof plants.  Most nurseries know what drought tolerant plants to install on the ground, and the peanut might have worked well at the hotel site on the ground.

Yet, rooftop ecology needs are nowhere near the same as ground level landscape requirements.  Leaf surface temperature differences can be as high as 80-90 degree F greater on the roof than on the ground.  Find a green roof nursery specializing in green roof plants that has worked for years in your area.

Dead green roofs are fire hazards

Wind too can have so much more impact on the roof than on ground level.  Perennial peanut's success on the ground is due to a hyper-fast photosynthesis rate and biomass creation.  The plant grows fast and covers the ground quickly.  However because the plant does not possess significant spatial or time based separation and protection of the Calvin Cycle processes, roof level heat and wind can pull the water out of the plant faster than the vascular system can resupply.

Maybe as soon as rains started the plant may have 'greened' up (possibly), yet during the dry periods an unacceptable and serious fire hazard existed.

The landscaper had previous success with peanut on the ground.  But a Florida roof is unlike the ground.

Florida green roof design is all about the plants and not so much about the system.
Note too that because there is no handrail system, personal fall protection device attachments would have to be installed to protect maintenance workers.

Maintenance on a green roof should only be done by staff trained for working on a roof with personal fall protection equipment.  Never allow a landscaper on a roof unless they are properly trained and equipped with safety gear, including a hardhat, safety glasses, high visibility vest and personal fall protection gear for starters.

But even with the proper maintenance procedures and awesome green roof planting bed, someone never figured out that  it is 'all about the plants'.

Nice green roof system plus wrong plants equals dead green roof planting.

The fort in St. Augustine, Castillo de San Marcos, is built with solid coquina rock walls, continually buffeted by strong salt laden winds and exposed to intense sunlight.  But the walls support over fifty species of plants.  No soil media and no added irrigation.  Over time populations of native plants have made their self at home.

Castillo de San Marcos plant's teach us that here in Florida it is not so much about the rooftop growing system.  It is not so much about the soil media, although the wrong soil media will not support long term growth.  It is all about Right Plant Right Place on the green roof.

So if you want to design a Florida Green Roof you can learn via trial and failure over the years, or work with a plant person who understands rooftop ecology.

We are presenting a series of design articles covering the basics of rooftop plant design.

So follow our green roof modeling discussion on the Greenroofs.com website under their Tropical Green Roofs Section.  Part one of the discussion was published a couple months ago.  Part two of the design discussion is coming soon.

The green roof has been removed.  What an amazing opportunity missed.
And for a quick revisit of the seven H's check out some of the other posts about designing Florida Green Roofs.

Once more, Green roofs in Florida are harsh places – remember the 7 (or more) H’s:
  • High Humidity
  • Hot, hot heat
  • High desiccating winds (killer)
  • Hurricanes (not the football team)
  • Hard Freezes
  • Horrible temperature swings
  • Hurtful droughts
  • Harmful floods
The green roof planting system installed above was really amazing.  But forcing those plants though they may grow great elsewhere in the states, that are not suited for the 7H's, on a Florida green roof was not the right approach.

Then hiring a landscaper without a rooftop background to try and remedy the problem only magnified the issues leading to failure.

Thank goodness the landscapers did not fall off the roof.  Thank goodness a cigarette ash did not land on the dead vegetation.

It is not really about the system.  On a green roof, it is all about the plants.

A green roof is all about the plants.

Tuesday, May 20, 2014

Native Plant Patterns and Historical Rainfall Trends, Predictors of Green Roof Plant Success

Climate and weather patterns are the most significant determining factors of what plants will go on your green roof project and so, rather than turn on the TV I like to look at historical weather maps.
National Weather Service's Historical Rainfall Maps
Green roof plant modeling process considers light and wind to be the two primary design variables for factors affecting green roof plants.  Sunlight relevance to green roof plants and for that matter even ground level landscape designs is usually referred to in terms of 'Photosynthetically Active (and Reactive) Radiation, or PAR.  Too much PAR and the plants can burn, desiccate and wither.  Too little PAR and the plants fail to grow.

Along with PAR is the photosynthetic pathway of the green roof plant and a host of other survival mechanisms such as photoperiodism, phototaxicity and phototropism.

Wind impact too is a design variable that must be accounted for during green roof plant layout.  Strong desiccating winds can harm green roof plants with as much severity as PAR overload.  Wind can pull so much water out of a leaf that the plant's vascular system will be overwhelmed and interestingly, no matter how much green roof irrigation is added to the planting bed, the plants still die.

Micro-irrigation usually alleviates the stresses of long droughts and so on those green roofs, available rainfall impacts may not be as much a controlling design variable (though still extremely important) as wind and light.

Still I find it very interesting to study rainfall patterns across the U.S. and across the world.  Nature has laid out and sorted the different types of vegetation across our continent in a manner relating to wind light and also according to rainfall amounts.

Yes, it is a simple and very broad generalization to say that following Mother Nature's lead supports project landscape or green roof plant potential success.  

When I look at the above map depicting historical rainfall amounts published by the National Weather Service, I see three main, broad patterns.  The Northwest and the East (red and orange areas) receive most of the rainfall across the U.S.  Broad leaf dicots and C3 monocots fill these regions.  Florida and the Central Plains (green areas) receive less than average precipitation and are vegetated with great stretches of grasslands.  Here in Florida the pine flat woods which make up much of the state are filled with C4 ground cover grasses such as the Andropogons and Sporobolis species (if you live in Pensacola though you may want to choose wetland plants for your green roof due to all the rain they have been receiving lately).  Finally, the areas depicted by the least rainfall amounts (less than 20 inches per year - light blue geographic regions) are inhabited by cacti and other succulents.

So if I were designing a green roof for an area outside of Florida I'd think of this map first.

I may or may not end up following Mother Nature's lead after examine a complicated host of other factors, including client intent and if I choose not to follow then my green roof planting design better be spot on in producing the ecology my selected green roof plants will require.

The roof is a seriously harsh place to grow plants.  Use of Mother Nature's millennia of trial and error as guidelines for selecting green roof plants is smart green roofing.  It is hard to beat local native plants on the roof or across the ground.

Thursday, May 8, 2014

Florida Low Impact Development, A Native Plant Bioswale Success!

The Lasalle Street storm water bioswale is growing into its third spring, a little over two years old.  I know because my aorta dissected during the middle of the project's schedule. Ugh.  A first year plant and project review can be read here while photos and several posts of the original planting project can be found here.
Native plant Bioswale, Lasalle St., Jacksonville, Third Spring's Growth

Today the array of native plants installed by a marvelous group of volunteers has grown into their own prime, lovely Florida grasses, native shrubs and the wonderful cypress tree, Taxodium spp.
The Native Plant Bioswale was originally planted in late 2011
Bioswales are rapidly becoming one of the more popular approaches to cleaning urban storm water runoff and most are using native plant species.  The University of Florida IFAS Extension Service has produced a helpful, informative publication on the design and benefits of urban bioswales for Florida cities.
The Bioswale has matured into a prime example of a successful low-impact development project

We think of plants on green roofs providing many benefits, including;

  • Sequestration of Carbon and mitigation of CO2 greenhouse gasses
  • Positive production of fresh oxygen daily
  • Cleaning rainfall runoff by filtering out particulate matter and attenuating flow rates
  • Uptake and sequestration of nutrients such as nitrogen and phosphorous
  • Habita creation for small to large wildlife and birds
  • Beauty for us humans
  • Urban Heat Island Effect mitigation - cooling of the cities
  • Keeping our creeks, lakes and rivers clean
  • and so much more
Bioswales provide the same benefits as green roofs.  Bioswales are like a green roof but are located directly on the ground instead of a rooftop.
Bioswales, like Florida Green Roofs provide an array of ecological and environmental benefits

Plants are so amazing, especially Florida native plant species.  They work 24/7 to help keep our world clean and that is just the start of what they really do for us!
Lasalle Street Native Plant Bioswale's Third Year Growth



Tuesday, May 6, 2014

Tree Ring Music - Melody in the Urban Core

I love plants.  When I heard about tree ring music on the record player, I had to share it here.  And we do have trees on some of our green roofs, like the Grancy Greybeard atop the Breaking Ground Contracting Green Roof.  I like the Acer music so much.  Enjoy!
For a full listing of tree ring music see Bartholomäus Traubeck's websitehttp://traubeck.bandcamp.com/album/years

Monday, May 5, 2014

Florida Green Roof Plant Root Structure, Horizontal Root Architecture

Green roof plant architecture is an important biomechanical component of all green roof design, construction, installation and maintenance activities.  In the end a green roof is first, foremost and all about the plants.
Florida green roof plant root architecture - beautiful horizontal root structure
Without the happy, thriving plants, there is no green roof.  Possibly a brown roof but not a green roof.

I think the Florida extensive green roof root structure depicted here in these photos is simply beautiful.
Green roof plant root architecture -  horizontal root structure growing into anchor
An understanding of green roof plant root architecture is one of those fundamental design talents that every green roof professional should possess.  Some of you will have learned about green roof plant root architecture from years of observation, hands-on planting and study of how green roof species grow, others through educational programs.  I examine root structure across green roofs every chance I get.  

My preference is shallow soil media and unimpeded horizontal growing space for green roof plant roots.  I do not like sectional barriers that may limit horizontal root growth and ultimately cause root circling-root bound growth patterns.
These grasses possess good green roof plant root architecture - not too aggressive but sturdy
Another reason I prefer unimpeded horizontal root growth opportunity on a green roof is because I believe green roof plants will over time, relocate themselves or their offspring to the best place on the roof for their particular species survival.  Yes, plants do move through root biomechanic mechanisms.  It is poor planning to restrict green roof plant root architecture any more than necessary.  Just think of how many times you may have pulled a plant from a nursery tray or pot with twisted and circling roots that have practically strangled the plant.
An anchor system may keep plants on a roof during tropical storms
In addition to catering to the green roof plant through design of open space for root growth to occur we like to provide the roots an anchor to grow into.  There are many different approaches one can take when providing an anchor, including cables, mesh, netting or fabric.  By permanently attaching the anchor material to the roof you create a green roof plant growing system that may be resilient to tropical storms or cyclone winds.
Unimpeded root growth prevents strangulation of green roof plants
Using this approach we have created green roofs that have stayed in place when blown with 130+ MPH winds.

The grasses in these photos show this principle in practice.  Using a small, mock up green roof growing system these plants have embedded their roots into a nylon fabric, creating an impressive anchoring form of root architecture and growing in a well defined, horizontal fashion.
A good green roof plant architecture will create a monolithic growing mat with plants anchoring each other
While some prefer deep plantings with roots reaching down vertically, we find horizontal root structure strategically places roots in an optimal position to absorb those frequent one half to two inch afternoon rainfalls here in Florida.  Rain water usually stays in the top inch or so of the green roof soil media.  With a horizontal growth pattern, green roof plants can take advantage of this rainfall where deep roots may have less rain reach down into deeper soil horizons.

If you are wondering, the photographed soil media contains less than 5% organic material.  The bark-looking chips are actually ground recycled rubber tires.  This is an experimental soil media, one we do not use on actual green roofs due to fire ratings.

Know your green roof plant architecture.  Remember, in the end a green roof is first, foremost and all about designing a growing system that keeps the green roof plants happy, healthy and surviving in the long term.

Thursday, May 1, 2014

Intense Rooftop Aquaponics - Amazing Rooftop Garden!

Check out this impressive Rooftop Farm - Aquaponics - garden video.  It is amazing just how much food is being grown within a small rooftop area!


Efforts like these are truly inspirational and may hold the answer to feeding the world's future population.

Wednesday, April 30, 2014

Green Roof Roof Drains Reference Links

Sizing Roof Drains for Green Roofs (and All Roofs In Fact) is Important
I spent a good hour last night worrying about a new green roof we are working on, and how it would drain with the roof drains designed by the project architect.

Right away I will say that I am not qualified to design roof drains.  Sizing roof drainage is a function for a qualified architect or engineer, not a green roof plant person.  However, I still worry.

Living in Florida I have seen some heavy and prolonged downpours.  Last night in fact, across the panhandle area of western Florida, rainfall totals reached almost 24".  That is a lot of water to move off the roof.

Of course storms dumping huge quantities of water do not happen every day.  But I still want my green roofs to drain.  Most green roof plants do not like 'wet feet' so to speak and I certainly do not want the green roof plants to float off the roof.

Yes, I ultimately trust most architects and engineers on their designs for they are accomplished professionals.  But for those occasions, like last night I feel better after a second opinion.

Now I am not vouching for their accuracy, but there are several easy to use Roof Drain Sizing calculators published across the internet.  It only takes a few seconds once you have the approximate square footage of the roof you are wondering about to see just how many roof drains are needed for different areas of the country.

Do not use these for design, but like last night, when I was wondering if the architect got the design right, these sites may be a good second opinion.

So stop worrying and check out some of these Roofing Drain Sizing Calculators:


Sunday, April 27, 2014

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.


video

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.

Monday, April 21, 2014

Green Roof Videos

Sometimes I can't sleep at night.  My titanium aortic valve makes a racket at night and the Dacron aorta feels like an overfilled balloon bouncing around in my chest.  Times like these I want to watch #GreenRoof videos!  So I made my own collection of my favorite green roof videos and now it is easy to watch them over and over.

Here is one of my favorites:

https://www.youtube.com/watch?v=cbzOUC0UICo

I can learn from the pros, like Dusty Gedge and others.  I can also watch others and learn what not to do - like stand on a roof without rails and risk falling off to certain broken somethings or worse.

I am amazed at just how many greenroom websites include photos of obvious OSHA violations where staff are leaning over the edge of rooftops high in the air without personal fall protection equipment.  Safety First on Green Roofs!

Anyway, I hope you enjoy these videos and also do not fall off your green roof! I will be adding more and changing out other videos on a frequent basis.  Please email me links to your favorite green roof or living wall videos and I will try and include those too and give you credit for the link or video if you wish - send the links and comments here.

Sunday, April 20, 2014

Beat Your Florida Green Roof Wind Impacts With Rich Coastal Biodiversity

The very best way to understand how your coastal green roof (and for that matter any green roof) will preform is to visit the site as often as possible before the plants are installed.


I always say 'wind is the biggest killer of green roof plants' and there have been many posts about wind impacts in this blog over the years, including;

Wind and light are two of the most important green roof design variables.  We at MetroVerde consider light and wind to be the two primary green roof design variables to take into consideration when developing ideas for a green roof.

The very best way to know whether or not wind is going to impact your project is to walk the site as often as possible, in the morning and throughout the day and in the evening.   Wind impacts fluctuate depending on a number of factors, including time of day.

Sunlight, air temperature and gradients and many other variables can influence air movement.

My teen daughter and I took a walk along the Atlantic coastal beach this morning and the and was blowing!  The pier's flag was standing straight out and whipping back and forth and we estimated the sped to be about 15 meter's per second - almost 35 miles per hour.

Most any plants are going to suffer in winds that fast and many broad leaf plants will quickly desiccate out and possibly die, especially as salt deposition from the ocean spray coats the leaves, stems and flowers.

Over the years we have worked on developing a green roof model that identifies those plant families with good wind resistance.

A wind resistant plant will possess either light-time activated or embedded spatial separation and protection mechanisms for Calvin Cycle processes.

Parapets are always preferred as wind breaks but architects sometimes develop client-directed roof plans with little or no parapets.  In those cases we must use wind resistant plants to serve as living parapets or wind breaks to the inner green roof.

Thank goodness there are many plants that can survive the vicious onslaught presented by salt spray and winds though.
Florida Green Roofs, coastal dunes are rich in biodiversity with wind and salt tolerant plants perfect for #GreenRoofs

Which ones?

The very best was to know whether or not wind is going to impact your green roof project and to find out what plants can survive these blistering winds is to regularly walk the project site.  

At first glance the coastal beaches may seem to just be 'green' with sand spurs. Ha!  Closer looks will show just how complex plant biodiversity on the beach dune actually is.  There are many, many species adapted to those wicked, punishing salty winds.

The very best was to know whether or not wind is going to impact your green roof project and to find out what plants can survive these blistering winds is to regularly walk the project site. 

Time to go for a walk.


Friday, April 18, 2014

How Florida Green Roofs are Born - an Idea and a Sketch

Where does one start on a green roof project?  For me it is with an idea then a rough sketch.
Florida Green Roof ideas start with a client's idea, then to a sketch. Great projects start with a simple idea.
 Many times the first sketch creates more ideas and those thoughts open more doors to expanded imagination.

Sometimes the idea may be shelved, but I suspect never forgotten.  Once an idea is created the concept has been released to the universe and could be around for a very long time.

Fabulous art deco building in the planning process for rehabilitation.
This building will be a health food, yoga and coffee shop in the near future.  The owner desires to incorporate vertical green.  We start with an idea and a sketch.

Some of the first issues we discuss include:

  • Structural capabilities (the roof is reinforced concrete)
  • City permitting requirements for landscape and stormwater
  • Wind exposure
  • Sun intensity
  • Budget
  • Maintenance
  • Theme
  • Adjoining buildings, and
  • so much more
But all journeys start with an idea.  Like a seed, the first thought grows and begins to take root.  Soon new forms appear.  Over time the creation matures, one step at a time, beginning with an idea.

My advice to all green roof and living wall designers is, "dream and let ideas flow".

Tuesday, April 15, 2014

Plant Size Considerations for Green Roofs - Size and Weight Are Important!

Sometimes we may be inclined to add small succulents to a green roof planting scheme because we know they may be tolerant to just about every environmental factor encountered on a roof.
Agave are drought, salt, wind, heat and hurricane tolerant, but they will add weight to a green roof!
Succulents can be deceiving with respect to size and weight, especially to those who have not worked long term with these plants and seen their size at maturity.  What may be a tiny, perfectly sized immature succulent may turn into a very large and heavy specimen with age.
Potential Florida Green Roof plant or potential roof problem?
Root architecture too is another important consideration for the green roof designer to take into account.

Some succulent plants develop swollen root tubers for water and nutrient storage.  Additional water means heavier weight.  Moreover, some of these roots grow in a very aggressive fashion and can damage an underlying single ply membrane or asphalt shingle roof.
Potential green roof plants have also have aggressive root systems that can damage single ply or shingles
While some small succulents, like sedum may never grow six feet tall, others can.  Though the succulents and cacti you plant may do wonderfully for the first several years,  over time they may outgrow the roof's planting bed.

Problems arise when these overgrown plants present weight issues with respect to the loading capabilities of a supporting roof structure.  An extensive green roof with smaller plants may weight twenty to thirty pounds per square foot or 100 - 150 kg/sm.  The same extensive green roof with 5' to 6' agaves may weigh three or four times the original weight.

Wind resistant can be another important factor with large plants on a rooftop, especially in hurricane impacted areas.

When you increase a roof's live load fourfold you may cause structural failure issues.

Treat some succulents as potential large shrubs or small trees.  Remember, just because a small succulent looks just right for your green roof doesn't mean it will stay that way.


Monday, April 14, 2014

Green Roofs Can Cool Cities, Learning From an Endurocap

Green roofs really do cool buildings through plant transpiration and I proved this yesterday to myself by example with an inexpensive but highly effective cap called the Mission Enduracool cap.
My Mission Enduracool cap teaches me about green roof cooling effects.
Green roofs and Mission Endurocool cool based upon the same principal as air conditioners  - that of heat being absorbed into a liquid and the liquid transitioning from a liquid state to a gaseous state.

On green roofs and across my cooling cap the liquid is water.  Plants transpire water out of their stomata during the photosynthesis processes and I sweat water and salts.  Air conditioners usually evaporate a refrigerant like freon, but all there cooling processes are based around heat being absorbed into a liquid and the resulting gaseous phase that takes place with heat adsorption.

According to the US Geological Service (USGS) about ten percent of the humidity in the air is due to plant's transpiration.  That is a lot of water!

So because I cycle most everywhere I go, my head (just like a building's rooftop) gets hot from both metabolism and from solar gain.  I always wear a helmet but that piece of safety equipment does not do much to cool except provide a bit of filtered shade.

We have talked of green roofs and their insulation value before, several times in this blog, but cooling offers additional benefits over insulation.  Cooling actually removes heat whereas insulation just blocks heat.

My first bicycle trip out with the cooling cap was to Publix, our local grocery store.  Per the cap's instruction sheet, I soaked it  in water and proceeded to wring most of the water out, leaving the cloth slightly damp.  Snapping it over my bald head I took off down the road after turning my bike's safety lights on.  The cooling effect was immediately noticeable and amazing!

Green roof plants and their transpiration right away popped into my mind.  "Hey!  This is what is happening to a building with a green roof as plants loose water to the atmosphere through evaporation", I told myself.

There are many web resources pointing out the benefits of green roofs, and their cooling potential for the urban core.

For me the maxim, 'seeing is believing' rings so true.  I learn mostly from experience.  The cooling cap taught me yesterday about the power of plants on a roof and cooling the cities.

Riding my bike I felt as if I had an air conditioner in my cycle helmet.

Sometimes short, simple life experiences can teach us more than an entire college course.  Green roofs can cool cities, I knew this before but I am so much more convinced now.

Friday, April 11, 2014

Green Roof Soil Media Questions for an Ocean Front Green Roof

I have been asking myself a question over and over again lately.  How do I keep green roof soil media from blowing off a three story, ocean front residential green roof?

The Atlantic Ocean shore - great place to learn of #Greenroof plants and to build a green roof too!
I think I have the answer but I still am asking myself the question over and over.  Not because I have doubts necessarily, but because I want to examine the issue on a regular basis, over an extended period of time.

In the past I've had new insights arise when I regularly revisit a challenge.  Challenges, be they green roof related or otherwise, are usually solved if one puts enough thought into resolving the issue at hand.

This particular green roof project will be a challenge.  Weight will be a factor as it always is.  Light will be intense and strong, all day long with no shade available.  Salt spray will be constantly coating the plants.  Hurricanes are very likely as the house sits right in the middle of hurricane alley.

But I am as confident as any experienced green roof designer can be that all these variables will  be addressed in a manner that will minimize risk to the structure, plants and surrounding area.

The daily wind factor keeps coming back into my mind though.

Any green roof will have the potential to experience much higher wind loadings.  A green roof on the ocean front usually has much higher velocity daily winds whipping across the soil and plants.  Keeping the plants alive and free from desiccation is one issue and keeping the soil media from sand-blasting a neighbor's house is another design goal (as well as simply keeping the soil media on the roof).

Ocean lots are a challenge to the #GreenRoof designer for many reasons
Sand has it's advantages and disadvantages.  Coastal dune plants, those species that will survive on a roof such as this love beach sand.  But sand has a tendency to be blown around easily and is quite heavy.  The sand here is primarily a lovely brown hue and composed mainly of crushed coquina shell, full of calcium and other trace minerals.  It drains well and holds an adequate amount of moisture.

But I am not thinking sharp beach sand would be good on the roof.  With average daily wind velocities from 5-6 meters per second up to 10 MPS and higher, I am concerned beach sand would be blown away in a matter of days, if not hours.

Walking the beach not only relaxes but teaches much.  I see things on my frequent seashore strolls that remind me of how Mother Nature behaves.  She behaves as she wants too, with little to no regard for us humans and our designs.

Mother Nature and wind has a mind of their own with regards to sand deposition #greenroofs
I view seawalls constructed with many thousands of dollars intended to hold sand in one place or keep sand out of another place and despite our best efforts these structures ultimately always loose the battle. Mother Nature puts sand where her wind blows and in other places too.

Perhaps a larger diameter, lightweight inorganic substance like expanded clay may be better.  We will analyze this in future posts.  A mature, developed green roof plant root system will go a long ways towards holding soil media in place, but can take a couple years or more to for the roots to develop and I don't want the clay to come off the roof and act like shotgun pellets in a tropical storm, damaging adjacent fenestration as ICC notes warn against.

Ultimately, root architecture may be the answer.  Comprehensive root coverage can hold soil media, plants and the green roof system in place even under storm conditions.

Agar-based tackifiers and netting have been used to prevent wind scouring of green roof soil media.  On the ocean front site I am concerned the tackifier would quickly degrade under the intense solar heat and constant salty mist.  Last thing I want to see too, is wind netting loosely flopping about after becoming slightly dislodged, perhaps beating the plants down in the breezes.

Sustainability too and green building programs call for use of local materials and are other considerations to take into account.  Sometimes local material compounding is practical or even the only way to acquire soil media.  Other times local materials may not be suitable for green roof soil applications.

Ocean front #Greenroofs face salt, wind, sun, storms and other harsh impacts
We don't want the soil media to be too dark because of high solar gain.  I spoke with someone yesterday who told me about a free roof that would not grow plants because the expanded shale was so hot he could feel the intense heat through his shoes.

We want the soil media to have a proper, plant friendly pH to encourage good plant growth too, and it needs to be primarily an inorganic mix also.

There are also many standards and reference materials to consult.

European FLL have been the most looked to standards for specification and design.

There is a simple but good short description of the green roof soil media question published by Design Cost Data here.

One of the most comprehensive and helpful discussions of green roof soil media is located on the industry website, Greenroofs.com .  The article discusses green roof soil media ASTM standards and provides links to other valuable soil media references, especially to an article by Chuck Friedrich entitled 'Don't Call it Dirt!'.

I've got a lot to consider concerning this ocean front structure's windy green roof.

Wednesday, April 9, 2014

Green Roof and Living Wall Soil Media - Vertical Green Begins Below Ground

Vines provide great vertical screening and greening capabilities, especially here in Florida where strong desiccating winds can quickly overwhelm and dessicate a planted exterior living wall,
Coral honeysuckle, Lonicera sempervirens offers interesting color and texture as a living wall
 (unless one uses a non-native invasive species like Boston Fern, Nephrolepis cordifolia, which is never recommended).

One of the most important aspects of creating a beautiful, thick and lush living wall is sometimes never even considered, that being the quality and characteristics of the soil in which the vines are planted.

Unfortunately, many designers only consider the flowers or foliage, forgetting the roots though not seen, are so critical to leaf and flower development.
Native Carolina jessamine, Gelsemium sempervirens should be nice and thick but is planted in bad soil
In urban development projects the soil can be concrete rubble with a high pH.  In situations like these a beautiful stainless and expensive trellis and nice, hot house grown plants can end up looking terrible in a matter or weeks.
Coral honeysuckle planted in poor soils looks terrible
I've written about the Jacksonville Whole Foods living wall trellis system before - an expensive living wall system that looks pitiful, all due to high pH and other soil problems.  Soil pH is a measure of acidity or alkalinity in the dirt.
Living wall vines can become woody without proper soil, loosing their leaves
The health food grocer has a high-quality stainless trellis system installed near the front entrance and on the south side of the store building.  Yet the plants have not successfully established themselves and grown well.  The store has been open now for several years, allowing plenty of time for the plants to send down roots and add  upper biomass.

The present store facility was originally constructed where another building had been demolished.  It appears some of the original slab was reused, and significant amounts of concrete, crushed block and other previous building material was integrated into the soil during site preparation.

Most plants prefer a soil pH of between 5.6 up to 7.0.  Many native and adapted Florida Friendly plants vines require an even lower pH to thrive.

Soils with a high pH, such as the urban soils in the Whole Foods living wall planters, restrict nutrient availability (specifically iron, zinc and manganese), stunting planted vine growth and causing yellowing of leaves.

Although some soil amendments appear to have been added during final landscaping, the type and quantity were not adequate to encourage strong plant growth.

There are several simple remedies available to the Whole Foods site.  The living wall was installed in 2010-2011 and could have easily be supporting massive amounts of flowering, fruiting and beautiful vines by mid summer 2012.  Today it is 2014 and the vines still struggle to maintain a tiny about of leaf cover.

But a remedy is possible.  First there needs to be a minor excavation of existing planter soil, both around the front columns and then within the southern wall planter box.  This soil does not need to be discarded.

Second, an appropriate amount of ammonium based fertilizer should be mixed into the soil.  Ammonium based fertilizers typically contain ammonium sulfate or sulfur coated urea.  Ammonium and oxygen react to form nitrite/nitrate, water and hydrogen ions.  The hydrogen ions then work to acidify the soil.

One advantage urban soils usually have is the variety of soil particle sizes and if not over-compacted, can provide for adequate oxygenation of the soil.  Oxygen and ammonium provide nutrients for the plants and help counteract the higher pH of the urban soils.

A quick field test of the Whole Foods planter soils reveals significantly higher than normal  pH.

Amending with organic matter is another possible approach.  Composted pine bark, pine needles, oak leaves, properly composted food scraps can also release both needed nutrients and hydrogen ions into the soil.  Another benefit of the organic mulch route is that earth worms and other soil life will quickly create extensive micro-communities, contributing additional nutrients and providing for nature based soil aeration.

Once the Whole Foods planter soils are amended with the proper amount of ammonium based fertilizers, the soil can be replaced and plants installed.

Of course, care should be taken not to over-fertilize.  Excess amounts of ammonium based fertilizers can burn the roots of installed plants, creating a whole new set of problems.

Native and landscape vines alike can add vertical interest, privacy, screening, color and texture to a landscape project under almost any atmospheric conditions if they are growing in adequate soils.

Remembering that vertical green begins far below the ground is the first step to living wall design and construction success.