Green Roof for Landscape and Parking Lots - cleaning and storing stormwater

Green roof concepts are not just limited to the top of a structure.  They can be adapted almost anywhere plants, water and a platform can be integrated.  

Referring to the term 'volumetric green' in the Urban Core - green roof technology can be adapted to provide habitat, clean stormwater, sequester carbon, produce oxygen and create beauty across the cityscape.

Ultimately, to be cost-effective, a best management practice must bring cost effectiveness to the table.

Maximizing site development potential by combining stormwater, green space and other site functions allows for green practices to be more readily implemented.

Below is a diagram of what we've done with the lessons learned from building lightweight green roofs however the 'roof' is actually a landscape cover for stormwater storage and recycling.

"Green Roof" over Rainwater storage, cleaning and recycling system

One of the aspects about plants we have come to realize is plants are efficient with uptaking nutrients - nutrients otherwise contributing to algae blooms and dead waterbodies. 

As site development becomes more constrained with respect to available space, stormwater and wastewater treatment can turn to green roof inspired, plant based systems as a method of sequestering nitrogen, phosphorus, zinc, copper and other contaminants. 

Once sequestered, these pollutants may be removed through biomass harvesting and composted on-site for reuse in the landscape. 

Removing nutrients from the water cycle is the most efficient way of cleaning our water supply. 

Green roof technology applied to stormwater storage and recycling has many benefits.  Stored rainwater may be used for irrigation, flushing of toilets and more.

Combining landscape and rainwater recycling through green roof technology

Green Roof Technology applied to Stormwater Capture and Storage

Green Roof Drainage Issues

Drainage is an essential design component on any green roof.

Not enough drainage and the green roof can quickly fail via leaks, dead plants and even a collapsed ceiling.

Too much drainage and  the green roof plants may suffer from not enough irrigation.

Inspecting the roof before installation of the green roof system is very important.  Be sure to review the plans and find the elevation breaks, low spots and ridges.  Take the plans and try to determine how the rainwater and irrigation water, if irrigation water is used, will flow.

Inspect the roof for drainage breaks before installation of Green Roof System

Once the underlying roofing system is installed, inspect the entire roof.  Watch for issues with the flow of water, look for depressions formed into the surface during construction where water may pool.  Ensure seams appear to be properly attached.  Always insist on a flood test and conduct a metal sweep before commencing any work.

When you feel comfortable with understanding the direction of rainwater flow and other issues and requirements for the green roof and install the base system, be it trays, monolithic built-in-place or other system, the soil media will be one of the first components to be installed.

Soil media is usually premixed and possesses the same water or rainfall permeability no matter the location placed on the roof.  Filling the green roof system with soil media possessing the same drainage and water flow characteristics may be adequate, unless the roof pools water in places it shouldn't, or drains water away from areas where water needs to stay and provide irrigation to the green roof plants to be installed.

If your roof construction requires a change in water flow patterns across the roof surface you can easily accomplish the re-direction of water by substituting materials possessing different permeability and water flow qualities for the soil media in the affected area, or by placing a layer of material with increased or decreased water flow characteristics under the soil media.

This obviously requires solid knowledge of  the materials you are working with, their permeability, saturation rates and other physical and chemical qualities that may affect the roof drainage pattern.

Sand for instance can be employed to either slow down or speed up drainage depending upon the type of surrounding green roof soil media.

Peat and coir are other materials with varying drainage characteristics that may be successfully used to after drainage patterns to your requirements.

Adding peat to affect drainage flow

Adding peat under fast draining green roof soil media allows for additional rainwater adsorption and storage.  Peat moves water through wicking action, and can direct much needed irrigation towards the plants needing the water the most.

Natural and geo-synthetic fabrics can also be used to accomplish the same water direction exercise, or re-direction as is the case.

Though all of the above water distribution efforts should in reality be accomplished through proper design,  we all know that ultimately we must make adjustments after the fact sometimes to accomodate anomalies in the as-built system.

Understanding how to 'tweak' rainfall flow through the green roof soil media is important.

Doing so will allow your green roof to mature into a successful planting.

Mature Green Roof Planting, Florida (MetroVerde)

Green Roof Irrigation, Where are the April Showers?

Much of Florida has a unique climate, one needing to be understood for successful green roof design.

April is supposed to bring rainfall so we can have May flowers, right?  Maybe it is due to cyclical weather patterns or maybe to climate change, but over the past ten years or so excluding tropical storms and hurricanes the state has been in a drought.

Much of the Southeastern US and the Caribbean has experienced similar rainfall shortages.

In areas where irrigation is restricted to certain days or prohibited all together this can mean serious potential damage to green roof and living wall plantings.

Unfortunately, without expensive treatment systems, grey water cannot be used for irrigation purposes in Florida by state mandate.  Therefore keeping green roofs and living walls irrigated can be problematic at times.

Capturing HVAC condensate for Green Roof Irrigation

Rainfall deficits aside, daily water vapor is typically quite high during these periods of drought.  High air water vapor has advantages and disadvantages though.  On a positive note, HVAC condensate can be captured and used for irrigation purposes as shown in the above photo ( the five gallon bucket is used to illustrate how much condensate accumulates).  Ten liters per day per 1000 SF, 92 SM.

Air Conditioning Condensate to be captured and reused

Though it is good to reuse condensate water from HVAC systems, always make sure there is no biocide added.

On a negative note, hot days with high humidity encourage plasmodial and fungus growth.  Though native plant species thrive with certain plasmodial and fungal interactions, other non-native landscape plants can turn to mush and die overnight (many sedum species are prone to hot weather Southern Blight effect here in Florida).

Ultimately, in areas where long periods of dry, hot , windy weather potential exists, especially during long daylight hours, the chance green roof plants will suffer are greatly increased.

Remembering photosynthesis processes in plants during design - right plant, right place - mitigates potential desiccation and drought damage.  Take advantage of all site climatic conditions during design.

Plants survive long, hot summers on their own.  As green roof designers we need to understand all aspects of light, wind, precipitation and other eco-variable conditions the green roof will be exposed to.

Dew Catchers for Green Roofs - Nature's Irrigtion

Lots of information exists on creating air turbulence, humidity, condensation and collecting dew.

I'll post an article with links to more information soon however below are some photos of dew collection inspiration and then the actual construction and installation of a simple but effective dew catcher on a permaculture roofs - one with winter veggies planted.

As always - email your questions here and happy green roofing!

Kevin

Morning Dew is Often Everywhere

Morning Dew Collecting on Green Roof Plants

Designing a Green Roof Dew Catcher

Constructing a Green Roof Dew Catcher

Green Roof Dew Catcher Ready for Installation

Green Roof Dew Catcher Installed

Harvesting Rainwater for Green Roofs - Underground Storage Systems

EcoRain Tank Modular Rainwater Harvesting for Green Roofs

We've talked about water crises and irrigation of green roofs many times before.  Designing a green roof irrigation system to run off of rainwater instead of potable water is easy.

One of the biggest disadvantages of large rainwater tanks before has been the freight expense of bringing a large tank from the manufacturer to the site.

Many times the cost of freight exceeded the cost of the tank - and there are not many tank manufacturers so the tanks may have had to been hauled across the country.  Long freight hauls create large carbon footprints.

However, several new structural Rainwater Harvesting Systems are now available on the market that are collapsable and can easily be assembled on-site.  For a video of a very large underground rainwater collection system in Dallas, Texas click here (opens in a new window).

EcoRain Tanks Rainwater Harvesting System

One of the more green subdivisions in Gainesville, Florida, the Madera Subdivision, utilizes underground collection and storage of stormwater in several of their homes.

Collection of rainwater and subsequent irrigation of green roofs can be a valid method for allowing larger buildings on Urban Core lots previously designed with much smaller impervious allotment.  This applies also to historic residential areas where renovations are occurring.

Importantly, the Green Roof design needs to anticipate periods of natural drought where stored rainwater may be depleted.

The use of potable water should be only used in certain instances, and the green roof plant selection should reflect species that can utilize the stored rainwater, however are also drought tolerant.

EcoRain Tanks Rainwater Harvesting System

Typical Underground Rainwater Storage Systems for Green Roof irrigation are designed and installed with little effort.

First the seasonal high groundwater level should be determined.  This can be accomplished with the civil engineer or geotechnical expert.  For the homeowner, simply take a shovel, I prefer a set of post hole-diggers, and dig a small hole down until wet soil or water appears.

The Green Roof Underground Stormwater Harvesting System should be primarily installed above the Seasonal High Ground Water Level.

Size your storage system to hold a 24-hour storm event quantity for the surface area of the roof you are collecting from.  ARCSA has a great website about sizing and designing systems - click here - opens in a new window.

Modular EcoRain Tank Unit

You can use solar pumps to pump the water back up from the rainwater harvesting cistern to the green roof.

Unpackage your EcoRain Tanks and assemble on site, placing them inside the liner within the excavated cistern area (refer to the video above for illustrations).

Detailed design information is available from the EcoRain Tank websites - and at www.ecorain.com

Remember, we a growing population on this globe and conservation of all water resources is important.  Ensure your green roof plant designer is using species that are friendly to conservation of water!

As always, feel free to contact us with your questions!

Happy Green Roofing!

Nature Irrigated Florida Green Roof Panel 18 Months (no added irrigation) UF

Green Roofs can be designed to take advantage of nature-based irrigation.  The following photos depict a green roof test panel constructed at UF and non-irrigated, except for precipitation and dew for 18 months.  Planting density can easily be increased to add a more lush appearance.

Ultimately, the green roofing industry must address water shortage issues and adapt, like the Florida Friendly Landscape program, to reduced or zero-based irrigation.

The challenge will involve understanding air moisture content and how to capture dew.  Additionally, looking at similar Florida ecosystems (such as the Glades type ecosystems) can help with plant specification.  Engineered soils are important too!  Having a soil that carries just enough water without keeping roots too wet is critical.

Then there is heat management and wind control issues to incorporate.

Stormwater too, is a vital concern for the Florida Green Roof industry.

It is possible to compound Florida's stormwater problem with green roofs if we design systems incorporating Nitrogen and Phosphorus fertilizer and potable water for irrigation.  Think of the algae problems in many of Florida's rivers from lawn fertilizers.

We may be only a step away from creating even a far worse problem with hastily thought through fertilized roofing systems.

Sustainability must define green roofing, along with community acceptance, cost-effectiveness and technical accuracy.

Feel free to tell us of project success and failures you've encountered.


As always, email me with your questions here.

Happy Green Roofing!

Kevin

Nature Irrigated Florida Green Roof Panel 18 Months (no added irrigation) UF

Green Roof Irrigation and Dew Catchers - 5 Important Factors

Irrigation provided by nature exists and understanding how dew works can make the  Florida (or Arid Locale) Green Roof successful.

Here in North Florida we are in the middle of an on-going three and a half week drought with no rain in sight.

You put water in the birdbath and the water has evaporated by the middle of the day.

Our Urban Permaculture Garden is growing just fine but craves water.

We are abiding by the watering restrictions we have in place here set by the St. Johns River Water Management District.

Yet look at the following photo my daughter took early in the morning!  There was water everywhere, especially on the green roof plants!

Irrigating Green Roof Plants - Dew Catchers

The amount of available water for plants is truly amazing.

We have noticed several interesting factors:

1. Dew occurs early in the morning - before the sun gets too hot and evaporation occurs
2. Early morning dew allows more water to be adsorbed by the plants.
3. Waxy plant leaves - those typically found on recommended green roof plants - encourage the condensed dew to roll off the leaves into the root area soil.
4. Many plant leaves seem to possess a natural form that directs dew to the middle of the leaf, down the stem and onto the root area.
5. Dew seems to be most prevelant during dryer, cooler periods - and those factors correspond exactly with our dry season.
6. The amount of dew is significant, as much as drip irrigation may produce.

So Mother Nature is offering up alternative irrigation means.

And we here in Florida and across the world have a water supply crisis.

Again, I ask - why are we irrigating Green Roofs with costly potable water that truly has a high carbon footprint?

When Mother Nature offers irrigation up for free.

Over the next couple of days I want to discuss dew catcher design and nutrients found in both dew and rainwater.

Happy Green Roofing!

As always - email me with your questions and dont forget to check out Dave Hillary's Free Green Roof Mini-Course.

Kevin

Green Roof Irrigation System - Can Nature Support a Green Roof?

Green roof irrigation can be accomplished via recycled rainwater pumped up from a cistern, potable water supply, a combination of recycled rainwater and potable water or from mother nature alone.

Importantly, a green roof should look good and not dry.  A dry roof could be a potential fire hazard.  Remember how those dry Christmas trees would burn.  Of course, some - like Ducks Unlimited - used to burn their green roofs annually - but most of us would not want to burn a green roof.

Other reasons for keeping the plants watered on a roof include;
1. More photosynthetic activity - hence more CO2 uptake and more O2 production,
2. Greater wildlife habitat,
3. Increased nutrient uptake
4. and others.

However there are also valid reasons for not irrigating a roof.

There is a water crisis here in Florida and across the southeastern US.  Remember the water wars of Alabama, Georgia and Florida a couple years ago?

50% of all potable water usage is typically consumed via landscape irrigation use!  Over withdrawal of aquifer reserves causes sinkholes to develop, wells to go dry and contamination of existing supplies to increase.  Native plantings are encouraged and water reuse is a municipal practice on the increase.

Additionally, roof leakage is a serious concern.  Creating roofs that can withstand a pond-like body of water is expensive and may cause mold problems.

Mechanical systems, including irrigation systems are always subject to eventual failure.  If the irrigation system goes down and the plants are used to significant watering then they may quickly die.

If the system is hooked up to potable water then a flood may occur.

Maybe there are other alternatives.  In our opinion, with the rush to implement new stormwater rules and nutrient removal criteria in Florida, the FDEP and certain testing organizations have jumped to the conclusion that the only way a green roof can survive periods of little to no rain is to install irrigation.

A quick review of Florida literature results in few if any research articles considering alternative irrigation methods.

Granted, FDEP's new applicant handbook suggests using rainwater cisterns to recycle rainwater as an irrigation supply for vegetated roofs, however this is but a selling point for their lack of research on non-irrigated systems and also is seriously flawed.

Suggesting rainwater cistern and rainwater recycling is low impact development is wrong.  Here in Florida half the year approximately sees only minimal rainfall amounts.  Today we are well behind - ten inches or so in our average annual rainfall amounts.  That means all those vegetated roof plants so used to plenty of rainwater irrigation from the cistern are now going to have to be irrigated with potable water or reuse water because they are not acclimated to the dry periods.  This philosophy is 'Anti-Florida Friendly Landscaping' and is a scam.

Certainly there is room for having stormwater volume and retention on the roof and in cisterns, but this approach cannot be the only sanctioned approach for green roofs in Florida.  And because FDEP and various educational institutions are pushing the 'Stormwater Pond on a Roof' approach the Florida Green Roof Industry has to adsorb and deal with the results of those misguided efforts.

Back to green roof irrigation.

Certain nations, such as Australia, New Zealand and others are stepping up and conducting serious research on alternative irrigation systems such as utilization of dew and air humidity.

We should too.

Here in Jacksonville we haven't had rain in three weeks.  Our yards and gardens are dry as a bone.  I'm sure many of the irrigated green roofs around the state are pumping out potable water (all the stored rainwater is used up by now) to keep the green roof plants irrigated.

Check out the following early morning photos.  remember - no rain here in the past three weeks however early morning water is everywhere.

Green Roof irrigation alternative - collect morning dew

Green Roof irrigation alternative - collect morning dew

Green Roof irrigation alternative - collect morning dew

Check out the article on dew collection found at http://www.inhabitat.com/2008/06/26/harvest-water-from-the-air-with-fog-dew-collectors/  

Possibly the research topic of an inspiring student or professor, the potential is great and the market place calls out for such inventions.

Green roof design already has taken advantage of the potential of harvesting dew for irrigation, MetroVerde utilizes compact dew catchers around many green roof plants in the field, harvesting significant early morning water for the plants.

Moreover, early morning water is captured on a more efficient basis by green roof plants because high daytime temperatures and evaporation process have not begun in the A.M hours.

So remember, next time someone says "Green Roofs in Florida Must be Irrigated", pause and ask yourself - has this person really done their homework or are they trying to push an agenda past you without your knowledge.


As always, feel free to contact us via email.

Happy Green Roofing,

Kevin!

Green Roof Plants and Water - A Special Relationship

Click here for Masaru Emoto's clip of ice crystals forming while the U.S. National Anthem is being played.

To understand water is to understand the universe.

Water and green roofs have a special relationship.

Kevin