Monday, July 30, 2012

HVAC Air Intake Covered in Plants - Green Roofs and Living Walls Filtering Air Flow

Newton, the Ask a Scientist, Scientist - available for consultation from the U.S. Government - click here for Newton's Website... - 

...says 53 Liters is the amount of pure Oxygen the average adult needs to survive every hour.  53 liters is approximately 14 gallons.

You can see we use alot of oxygen on a regular basis.  Now picture your bedroom and night or your office during the day.  For estimation purposes we will use an office space of about 5,000 SF with a 9' ceiling and containing 24 employees.  The Office contains  336,600 gallons of atmosphere.

Green Roof Plants filter toxins and produce oxygen



According to Newton the air we breathe contains about 21% oxygen so the office will contain 70,686 gallons of oxygen.  Is this enough to last the 24 employees for a day?  Let's find out.

Each employee breathes 14 gallons of pure oxygen per hour - more if they are active but most office workers are sedentary - so each employee breathes in120 gallons per shift and the office as a whole breathes in 2,880 gallons of oxygen per shift. 

OK - that's plenty of oxygen to start, but within a month without the doors and windows being opened the employees will rapidly use up all the oxygen.  How old is your office?  How old is your house?  When is the last time you've flushed the air in your office or house?

Just think, without the windows being open, you are breathing stale air - air already breathed in many times over by others in your office or house.  This air contains not only stale exhale of others (and suspended germs) but volatile toxins off-gassing from carpet, furniture, paint and other manufactured goods in the office or house.

And the unfortunate part of the whole equation is - we keep our windows shut most of the time.

However, there is a solution - plants!  Plants produce oxygen as a by-product of photosynthesis.  Your personal oxygen machine is as readily available to you as setting a plant on your desk.

I suspect all employees would be happier if air intakes for HVAC systems (most residential systems are closed loop systems) were covered with vines and pumped full of oxygen.

Moreover, plants are extremely efficient at removing toxins from the off-gassing process.

Green roofs and living walls are a key component to filling our sometimes stale Urban Core with fresh oxygen.  Imagine buildings downtown covered in plants and those plants pumping out oxygen daily.

The roof-based vegetated air intake tunnel keeps a building roof vegetated and provides additional benefits, including;

1.  Cools intake air
2.  Shades the roof
3.  Removes airborne toxins, and more!


MetroVerde Intake Tunnel Alternative to Green Roof 



Additional benefits allow for reducing heat island effect, providing shade, cleaning stormwater, wildlife habitat and much more.

Restoring volumetric green to the Urban Core.

Green Roofs are the key to healthy cities.

Thursday, July 26, 2012

Green Roof Plants; Insulation & Thermogenesis Issues

All plants possess biological systems that directly impact our ecology and the immediate environment surrounding our day to day activities.

After purchasing a truck load of plants on Saturday we unloaded most, however forgot to remove all of the plants from the cab.

Though the night air was cold (6C) when I opened the truck door and climbed in to drive to the market yesterday evening, after dark, I was enveloped with warm, moist air and confused as to why - with the cold dry air outside - the truck windows were fogged over with moisture.  Then I realized the plants were still in the truck, taking in CO2 and pumping moist O2 back into the air.

After spending much of Saturday evening outside taking temperatures with the ExTech IR thermometer, the oxygen and moisture filled truck cab emphasized what I already knew - plant's biological process are complex and have definite effects on their surroundings.

Sometimes we forget just how much plants impact our environment.

However in addition to the wonderful visual greenery (again we sometimes take for granted), plants sequester CO2, produce O2, provide habitat for wildlife in the Urban Core, provide food, fiber and medicine, clean stormwater and provide a myriad of other functions.

All of these factors and processes impact green roofs.  Understanding how these factors interact with the building is important.

This weekend I wanted to gather additional data on heat and green roofs.  My questions were many and included;

* Do green roofs really act as insulation?
* Do green roofs act as a heat sink - storing heat - instead of being an insulator?
* Does green roof plant selection impact the energy efficiency of green roofs?
* Does green roof soil composition impact energy efficiencies of green roofs - and if so, how?
* and a host of other questions.

After spending several hours with the IR, examining plants and green roof systems after dark - and in 6C ambient air, I can say much data needs to be collected, many studies completed and analysis done before we really understand the dynamics of green roofs.

Just as with the fertilizer and irrigation issues (I am always amazed at how some promote green roofs as ecologically friendly and important yet insist for the inclusion of potable water irrigation systems and fertilizer applications), the insulation or heat sink issues just don't seem to be adequately answered.

After collecting temperature data from under green roofs we see a green roof behavioral trend pointing to a heat sink rather than an insulator type system.  In other words, green roofs may tend to absorb heat during the day and then slowly release it back into the atmosphere and building during cooler evening hours.

Yet the complexities of plant species, plant growth characteristics, root systems, stomata to leaf surface area ratios, soil media specific heat qualities and other issues all contribute towards a complex model.

Getting back to the IR thermometer field  foray, some of the more interesting observations we noted were;

* Night time green roof plant leaf temperatures were approximately the same as ambient air temperatures,
* There were variable levels of warmer temperature readings found in the air space under the green roof plant leaves and above the green roof soil media, depending on the time of night and wind exposure - suggesting a level of insulation occurring as a result of leave structure
* The underside of an extensive green roof (3" soil media) stayed 10F warmer than a similar roof with no green roof system - and stayed warmer all night -- up until 5am the next morning,
* Banana plants stayed considerably warmer than ambient air for up to three hours after dark - unlike other plants,
* and other observations.

The banana plant elevated temperatures pointed us in the direction of thermogenesis in plants.  Thermogenic plants are those plants that can generate heat as a result of biological processes. The voodoo lily, Sauromatum guttatum, can generate temperatures of up to 110F - 32C!

There is a great video on thermogenic plants here.

However, the banana plant is not a thermogenic plant and the reason the banana plant stayed warmer than ambient air for several hours after sunset was the plant's high water content.  Water has one of the highest specific heat values of any compound or substance - four times than of limestone for instance.  Because the banana tree was full of water, the solar heat gain experienced during the day only slowly dissipated after nightfall.  Banana trees stayed warmer than most plants after dark because of the heat stored in the large volume if interstitial water within the plant.

It is possible the succulent filled extensive green roofs we are studying that emanate heat throughout the night are behaving like the banana plants.  The combination of green roof soil media and the water therein is absorbing heat during the day - maybe quite a bit of heat - then slowly releasing the heat at night.

The factors involved in modeling this complex heating and cooling dynamic are many and not well documented today.

We think the heating behavior of the extensive green roof is due to water in the extensive green roof plant root systems.  Because the system studied was non-irrigated (nature only irrigation), the soil media was rather dry.  However for heat to continue to be released for long hours, the heat source probably was water - and probably water stored in the underground parts of plants.

We ask ourselves many questions - if water is a significant heat sink and heat source, then do green roofs really act as insulating systems?

If green roofs are heat sinks then how much heat do they dissipate back into a building at night?

Are irrigated green roof systems actually hotter than non-irrigated vegetated roofs or reflective white roofs?  If so by how much?  How much cooling does plant transpiration and evapo-transpiration on irrigated green roofs?

There are many questions to be answered.

As an industry we need to sponsor and encourage more study of green roof thermodynamics.

Thursday, July 19, 2012

Green Roofs and Hurricanes, Wind Events and Tropical Storms

Hurricane and cyclone season is here.  The month of May marks the time each year when the National Hurricane Center says potential for tropical storms begin.  We are in the middle of July and have already had numerous tropical storms hit here in Florida.  Though wind damage was not as bad as it could have been, flooding was severe in certain areas.


But we are moving into the heart of summer and with warmer waters, one should expect an increase in tropical storms and cyclones soon.

Residents of areas prone to cyclones are familiar with the damage high velocity winds can do to buildings and especially roofs.  It is important that any green roof design installed on structures in Florida or other tropical climates subject to storms be fully tested with hurricane simulators for resistance to blow off and destruction.

Hurricane testing of green roofs is important for several reasons.


University of Florida Hurricane Simulator


First is the health, safety and welfare of people.  Placing any object on a roof not permanently attached is a violation of many building codes and can cause serious damage when blown off in high winds.

Parapets and other wind breaks around flat roofs may help up to certain speeds but trays, mats, pots or containers must be permanently attached.  This means each pot and each tray.  Otherwise liability in negligence may exist (consult your construction tort attorney) if the system blows off and causes damage.

Hurricane simulation testing is not the same as wind tunnel testing.  Be sure your green roof system has been tested out-doors on an engineer designed roof testing system with a wind turbine process.  Wind tunnel testing may not offer sufficient design support to protect against negligence (again consult your attorney).

Secondly, a good designer wants to know if the plants they are specifying will hold up in hurricane conditions.

Many plants may loose upper leaves but their root systems stay in place and they regrow quickly.  There are many good reference articles available on the when concerning right plant selection for hurricane prone areas.

I like built in place systems for hurricane prone areas.  Unless modular systems are permanently attached - I suggest permanently attaching each tray with adhesive - and a blow off occurs with resulting damage - then the issue of tort liability potentially arises (consult your attorney).  In our litigation prone society it is prudent to always hurricane test green roof systems before specifying and installing in those areas possibly subject to tropical storms.

Cyclone winds flowing across a flat roof create uplift like a vacuum and can pull shingles or other roofing material up into the air.  Roof accessories such as pipes, vents, skylights, green roofs, planters and HVAC units are also subject to the wind stresses and may become problematic.

Green roof hurricane preparedness involves several fairly simple and straightforward steps, including;
  • Make sure there are no loose objects on the green roof, such as pruning shears, hand trowels or other hand tools
  • Check to see if there are any dead plants or large pieces of fallen plant material and remove
  • Inspect the green roof system for integrity
    • If the green roof system is a tray system, make sure the trays and not damaged by UV degradation and ensure no loose edges are exposed
    • If the tray system is a mat system, check for loose mat edges
  • Review the underside decking in the attic for any water stains or other indicators or leaks
  • Check to make sure the underlying structure is holding its form and nto sagging fromt he weight of the green roof
  • Replace organic material and soil amendments as needed
  • Look for adjacent dead tree branches or limbs that could fall on the green roof and have removed
  • Make sure there are no mechanical system repair parts left on the roof from maintenance - you'd be surprised at what gets left on a roof - look for loose screws especially!
Well established green roof plants create turbulence across a roof surface, and may act to reduce uplift in some instances.

We'll be posting several articles over the next few weeks dealing with the  topic of winds and green roof plants, with a focus on cyclones, hurricanes and tropical storms.

Tuesday, July 17, 2012

Green Roofs and Living Walls are Really Just an Adaption of Raised Bed Planting Theory

If you understand raised bed planting theory you know most of what living roofs and walls are about.  Many times people think there are secrets to green roof and living wall design.

In fact, the corporate world has tried to patent many systems that are merely raised beds.

So expand your design considerations today by thinking of green roofs and living walls, not as a mysterious, high-tech approach to growing plants.  Think of your next design project where you need plants (be they flowers, food, natives or landscape specimens) as a raised bed.
Green Roof projects are like Raised Beds!

Questions to ask yourself include;

  • What will your soil media be comprised of?
    • Should be lightweight, well-drained not made from exotic synthetics heated in ovens to thousands of degrees for expansion or molding.  I like simple things, like sharp sand.
  • What are your raised bed (or living roof/wall) side walls made of?  
    • Stay away from materials that are flammable, UV degradable or contain toxins.
  • What plants do you want to use?
  • What is the root architecture of your chosen plants similar to?
    • Do you have deep roots?  Shallow root requirement?
    • Root architecture will direct your soil media depth design.
  • Try and stick with plants that provide food or are pollinator attractors.
    • I like native wildflowers but many designers stick with the tried and true succulents or sedum.
    • Food plants are also wonderful for rooftops and walls if protected from winds.
  • Where will the irrigation water come from?
    • I hate adding water to a roof.  They all eventually leak....but if water is already there, like AC condensate - use it!
  • Views
    • Plantings are mostly always pretty - make sure they can be seen.
  • Access
    • Can you get to the raised bed/rooftop or wall garden?
  • Dont put a raised bed on top of a septic tank and neither install a rooftop garden on a weak rafter system.
    • Common sense
  • and more...
The point here is - think of a rooftop design as a great raised bed in the sky.  Don't wait for the right 'system' to come along.  Go for it, design and install!

Sunday, July 15, 2012

Permaculture & DIY City Farming - Patio, Backyard, Roof & Walls

Over the past thirty years we've accumulated much hands-on experience with growing food, flowers, fiber and medicinal plants in the Urban Core.

City Farmed Permaculture Eggplant
Many approaches we tried turned out to be les than optimal.  However we considered even the failures to be successes for we knowing what doesn't work is just as important as knowing what does work.

City Farmed Permaculture Bell Peppers
City farming can occur anywhere where sunlight is available.

Of course, rain or condensate helps.  But we've successfully grown plants and seen plants grow in the most harshest of places, without soil and without additional irrigation.
City Farmed Permaculture Oranges
Growing lightweight food gardens on roofs has taught that even without massive roofing supports and even in cyclone prone areas, beans, tomatoes, herbs and greens can be grown.

Living walls can shade windows, provide habitat for wildlife, produce food, gourds and sponges.
City Farmed Permaculture Cilabtro
Patio space may be utilized to create highly efficient food gardens in self-watering containers.

Hens, geese, ducks, turkeys and rabbits all have a place on the Urban Farm.
City Farmed Permaculture Chives
Learn about rooftop gardening, how to build a low cost, highly effective chicken coop or seed starting greenhouse.

Understand biodiversity principles of plant selection.

Urban Farming - our best dreams and worse nightmares.

Know what you are geting into before the adventure of your life!

You can read the details in our approximately two hundred page City Farming book available on Amazon Kindle!

City Farming, Lovely Urban Insanity is available exclusively through Kindle by clicking the link here!

Tuesday, July 10, 2012

Small Residential Green Roofs for Fun, Food, Stormwater , Permaculture and More!

It is always good to talk to other green roof and Urban Core green/permaculture enthusiasts.  Yesterday I was fortunate to speak to Alan Myers-Davis, a Senior Project Manager at Living Roofs Inc. of North Carolina.

Photo by Living Roofs Inc. of North Carolina


Alan brought up the topic of small, lightweight green roofs for residential applications, sheds and garages.

There is a huge opportunity for America to green her Urban Core, small rooftop section by garage by shed by small rooftop.

Alan reminded me that our focus doesn't always have to be on mega-sized projects to make an impact.  Take Rob Overly's small one meter square green roof section that intercepts and cleans almost three hundred square meters of rooftop runoff (See a photo of Rob's green roof here).

Kudo's to Alan and Living Roofs Inc. of North Carolina!  See his note below the photographs.

Photo by Living Roofs Inc. of North Carolina

Photo by Living Roofs Inc. of North Carolina

by Living Roofs Inc. of North Carolina

by Living Roofs Inc. of North Carolina



Homeowners are extremely interested in green roofing and are always interested to know if they can transform their own roof into a living, breathing system.  

Unfortunately, buildings in the southeastern United States are not built for the same structural load capacity as northern buildings simply because we do not receive as much snow.  

Sometimes, the cost to retrofit an existing structure for increased load capacity can outweigh green roof advantages and homeowners are sent back to the drawing boards.  

Living Roofs, Inc., a green roof design and installation company based in Asheville, NC, has recently launched SHELTER to give homeowners another creative option for greening backyard space.  

These architectural drawings contain all of the necessary information required to build a DIY green roof garden shed…or art studio…or children’s playhouse…or even a man cave!  

The plan sets contain construction and green roof details, a complete materials list, and a very useful green roof resource list.  These are professionally rendered documents, so load capacities have been taken into consideration, and they have been designed small enough to bypass building codes.  Whether you wish to build the exact design or use the plans to modify and tweak your own design, they are a perfect introduction to back-yard green roofing and offer homeowners an outlet for some green creativity.  

There are two designs:  a more traditional gabled roof and a single-sloped, more contemporary roof.  The single-sloped roof comes in a 4” inch version and a 6” version, which allows for a more diverse plant selection of flowering perennials and grasses.  

Contact Alan Myers-Davis, Senior Project Manager at Living Roofs Inc., with any questions, and go to their Small Green Roof page on their website to view similar projects.  Cheers and keep on greening!