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Energy Cost Savings Through Green Roofs: A Myth

Green Team at Green Roof Technology, - Monday, June 10, 2013

An Executive Summary of Facts by Jörg Breuning

It is unavoidable and common sense that wearing wet clothes in winter will end up in hypothermia. Wearing the same wet clothes on a hot summer day, might actually help to feel cooler - not to be confused with feeling more comfortable. If we have only one set of clothes, for all four seasons, they would typically be made up of two layers. The first layer protects against direct environmental impacts such as sunlight, rain or wind and the second layer usually consists of a breathable layer for comfortable wearing and controlled air circulation. 

Source: Columbia

I have learned on my travels all across different desserts on earth that these layers reduce temperature increase on hot, sunny days, but at the same time can reduce the loss of body heat during extremely cold nights. Indigenous people of extreme environments have learned this lesson over centuries and were able to survive under these circumstances with this simple layer strategy. My father always used to say: "What is good for the cold is also good for the warm."

 Any man-made structure is nothing more than a body that requires consistent 'body temperature' to make it usable for the purposed design. A building without reliable all-season clothes is worthless or requires a tremendous effort (energy or operating costs) to make it useful.

Helping to make a building useful for people, the 'coat' consists typically of an insulation layer covered with a layer to protect against the elements (waterproofing, roofing membrane). Since we all know that the protective sheet will deteriorate over time this sheet (waterproofing) has to eventually be renewed, a process experts call re-roofing, which usually happens every 18-25 years.  

It is proven by my experience (since I have been designing and installing green roofs for 35 years) that a green roof can double the lifespan of the roof. The green roof acts like an additional all season two-layer system on top of the roof where healthy plants are the first layer, protecting against direct environmental impacts. The green roof growing media (green roof soil) is the breathable layer.

There is only one difference; the breathable layer (growing media) on a green roof is also the basis for the well-being of the plants and must be able to store water and air at the same time for a healthy growth. If this layer doesn't fully support the plants (and only the plants) the entire coat does not function and the plants tend to indicate this by suffering or a change in plant varieties present.

Above we learned that a wet coat in winter causes problems because water is not a good insulator and so we have to consider heat loss in winter when speaking about green roofs. We also understand now that dry green roof soil in summer will store heat (in the aggregates) and increases the cooling needs.

A green roof (and green walls that grow on growing substrates on vertical surfaces with consistent irrigation) are only thermal masses with hardly any insulating values. Considering these facts, building owners should be cautious when someone tells them that green roofs are good insulators. This is just not the case, especially if the building envelope is not insulated correctly in the beginning. Fixing heating and cooling loss simply through green roofs and/or green walls is impossible or a short-term solution.

With all the current research in this field, it's surprising to me that people still claim green roofs are good insulators. Additional insulation below the original coat is necessary (waterproofing or walls) to make the most effective roof (cost wise and physically) compared to any vegetated layer combined with growing media of growing substrate.

However, the thermal mass "green roof" certainly has lifespan extending properties for the waterproofing (and again, I can confirm this with projects spanning over 35 years). This is the key to start thinking in long terms (50+ years) in the building industry and is the most sustainable approach. Longevity is hardly considered in LEED™ certifications and with less emphasis on longevity, many awarded LEED™ buildings might fail for a certification because they can't be upgraded easily when the costs of energy increase. I am not referring to how wasteful the footprints of many of these 'innovative' building designs are.

Photo DM Products: Penn State's futuristic Millennium Science Complex earns LEED Gold for this space-wasting empty over hang. The 'water head' of the campus (or of their bureaucracy). Pants can not even grow underneath - how can people survive?

In the last 35 years, energy costs increased eight to ten times (!) and are expected to grow accordingly over the next three to five decades (or the lifespan of a green roof). Knowing this, selling a green roof for insulation purposes will unavoidably end up in a costly disaster for the building owner. Removing a fully functioning green roof in less that 25 years after installation, simply to add to more insulation, meet future requirements or to keep heating and cooling costs low.

Green roofs do not extend the life span of selected, important building components dramatically. Increasing the lifespan of any building is the best environmentally friendly approach in the building industry and the most efficient way to reduce costs for the owner over decades. Although, if scientitst and green roof professionals often do not understand this unique property of green roofs and don't design underplaying components accordingly, the building owner won't be very happy in the future. In 20-25 years when parts star needing to be replaced, a second green roof will be the last choice of the building owner because it will simply be additional costs with few benefits as originally promoted.He might not understand why he should disassemble a perfectly functioning and well established green roof, precisely when certain individuals led him in the wrong direction in the past.

Conclusions:

•  As a building owner be careful when people try to sell you green roofs as a good insulator without mentioning that additional insulation is necessary for the building for future energy needs.

•  Building owners have to understand that any available research about the insulation value of green roofs reflect only a current snap shot and potential savings in a very short time period (less that half life time of a green roof) and they are worthless when the intention is to build for half a century.

•  There are no energy  studies completed over a 50+ year time span comparing a green roof (plus additional insulation) and a conventional roof that will be re-roofed with additional insulation 20 years from now (typical re-roofing practice)

Trust only experts that recommend additional insulation under the green roof because then they expect that your investment will last a human lifetime, which will be profitable but also affordable during this time. Designing the roof (or wall) to last for five decades or more requires a lot of responsibility and expertise of the designers - if they value their customers.

 

Most Economic Green Walls

Green Team at Green Roof Technology, - Saturday, August 25, 2012

 Paris Green Wall

 

Some decades ago Patrick Blanc, French botanist working at the French National Centre for Scientific Research and specialized in plants from tropical forests created and introduced a unique design for a vertical garden with real plants (Vertical Garden, Green Wall or Mur Végétal). His simple system or other much more sophisticated systems are based on a consistent water and nutrient supply comparable to horizontal high tide/ low tide (Ebbe/Flut) systems in super-efficient nurseries. These systems often include artificial light and heat/cooling for sustainable growth.

Without being a horticultural expert Patrick Blanc was able to start a new trend utilizing horizontal plant propagating systems applied to the vertical as living art. Maintenance and operational costs of all these wall planted systems are very high and so the environmental benefit is certainly questionable. Typically in less than 10 years costs for maintenance and replanting increase the cost for installation without considering the high consumption of energy and water. 

Today when you fly in to Paris Airport Charles de Gaulle you will see multiple, small green walls - very attractive, lush green with an appealing biodiversity. Closer investigations discovered that these walls the next step of green walls that are super-efficient and extremely low cost for installation and maintenance. The systems at Charles de Gaulle Airport in Paris don’t need any artificial lights, they are completely disconnected from any power and water source and they are very efficient dust collectors. The amazing biodiversity has potential for the highest LEED rating.

Here are a few plants identified:

  • Attractiva plasticifolia (grown out of recycled content)
  • Fakefolia polychloridenses (PCB senct)
  • Metatrashus recyclisa (never green invasive)
  • Ripoffera myclientus `Variegatus´ (native)
  • Hidensia polyestertonia (forever green)

 

Good art reinvented.

Dr. Phil O. Dendron, Bel Air,  August 26th 2012,       

Pittsburgh Goes Green

Green Team at Green Roof Technology, - Thursday, June 14, 2012

By Kat Harrold

 

Photo by Jorg Breuning

This past week Kat Harrold joined Ian Cooke of Monrovia and Mike Coraggio from EcoWalls for an ASLA green wall lecture series.  The trio gave an informative presentation on vital elements to consider from design phase to maintenance of green walls.

Ian charmed the audience with illuminating and entertaining descriptions of key specimens to utilize for climbing green walls.  He also provided a nice over view of different systems and materials to consider when selecting green wall support systems.

Kat provided detailed climbing green wall information from a case study of a recent project.  The case study discussed the evolution of the project from the architects concept drawings to plant selection and custom planter designs.  This project demonstrated how once can create an inexpensive and ecologically effective outdoor green wall on a LEED retrofit.

Mike finished up the presentation with beautiful creations that only he and the Imagineers of Disney could dream up.  Intensive green walls for both indoor and outdoor displays lit up the screen with a variety of themes and ornate designs showing the true aesthetic potential for this green medium.

 

 

 

Creating Biodiversity on a Green Roof

Green Team at Green Roof Technology, - Monday, June 04, 2012

By Kat Harrold

 

Photo by ~ Jorg Breuning

Creating biodiversity on a green roof or green wall is significantly different than restoring it on ground level.  On a rooftop there is no preexisting ecology to enhance; everything is from scratch.  In most cases the growing media is drastically different from the soil down below which in turn dictates what ecology can be supported.  Accessibility, high winds, and proximity to the sun can also be challenging issues for organisms.

Studies show that plant selection and depth of growing media have a greater influence on the biodiversity of a green roof than height.  In the translation of research covering the biodiversity of green roofs, “Where the Beetles are Crawling and the Honeybees are Humming,” the biodiversity found on green roofs as tall as 400 feet were comparable to that of lower green roofs.

Tray or modular green roof systems create the visual impression of a green roof by placing a series of planters close together.   The history of German trays, introduced in 1978, show that in most cases the performance of pre-planted boxes fail to meet performance and maintenance expectations.  The composition of a modular system simply does not provide the right set-up to reliably enjoy the 30 to 50 year lifespan expected from a built up equivalent system.  Additionally there tends to be incredible amounts of species die back during the first 5 years creating a sparsely vegetated monoculture setting.  These factors create a very poor and unreliable environment for biodiversity to take place.

Visit us next week for more information on bio-diverse intensive green roofs!

 

 


Green Walls: Your Friendly Green Neighbor

Green Team at Green Roof Technology, - Thursday, March 08, 2012

By Kat Harrold

 

 Photo by ~ Goldtex

Where square footage is at a premium the demand for green space has become one of the hottest commodities.  In a high rise apartment building one might consider the options quite limited.  Try thinking outside the box, literally, and imagine all the vertical space available. Where horizontal space is limited vertical gardens offer a green oasis in a concrete jungle.  

With the right plant selection outdoor green walls make wonderful neighbors.  A green wall composed of hardy vines can provide seasonal interest with an array of colorful leaves and fragrant blossoms.  Plant selection can also play an important role in attracting birds and pollinating insects.  

In spite of their good looks, climbing green walls can be low maintenance requiring only occasional pruning and irrigation depending on location.  Steel cables and wire-mesh grids can be used to support and train climbing vegetation.

Green walls can play an important role in energy savings.  By shading the building during the summer and providing insulation in the winter, green walls reduce seasonal stresses on heating and cooling.  The ideal location for a green wall to reduce summer cooling costs is the south facing side of the building.  The southern exposure receives the most sun light which can also be very beneficial to the vines.
 

IDS 2012 - Interior Design Show in Toronto Rolls Out the Emerald Carpet

Green Team at Green Roof Technology, - Wednesday, February 01, 2012

By Kat Harrold

IDS Show Floor ~ Photos by Jorg Breuning

Green Roof Technology is back from the premier interior design show in Canada IDS 2012.  At this show we were presented with the design challenge, "How do you live urban?" and responded with a challenge of our own, "How do you make the urban environment alive?" 

One of the most obvious and easiest ways to add green to the urban environment and make it come a live is to create a balcony garden or balcony green roof.  Where ground space is limited or not available at all, a balcony garden is the perfect solution for that green transition from inside to out.  Depending on your space, a green roof may be an easy low maintenance option.  For a more formal effect planters can be used to add a splash of color and create a dynamic space with height and texture.

For making a seamless transition from the outdoors in a green wall offers a compact and space saving solution.   Tropical plants offer a full pallet of color, shapes, and textures making even the bleakest winter days feel bright and lively.

During the warmer months or for a hotel lobby, a moss wall is a great alternative to a regular cement wall.  Studies have shown that the color green helps people relax which can often be a difficult achievement in the stress filled urban environment.  Meditation aside, the quality of air will be increased due to the filtration qualities of the vegetation. 

Vegetation, water, and fire all add exciting elements to our environment.  Some are green in color and others are green in function.  When selecting a fire feature, fountain, or green wall consider the carbon foot print of the feature.  Woodless fire pits are green alternatives just a closed system vegetated walls are the greener solution for irrigated green walls.


 

 


Endangered Fern Calls Franklin and Marshall Home

Green Team at Green Roof Technology, - Thursday, August 11, 2011

Cliffbrake Fern (Pellaea glabella) at Franklin and Marshall College - Kat Harrold

Franklin and Marshall College in Lancaster PA already has a reputation for being green as it sports a large collection of green roofs.  During the installation of their latest green roof on Schnader Hall, a "green wall" was discovered.  Clinging to a shaded brick support wall on the roof a collection of tiny ferns were found.  Upon further examination these plants were discovered to be Pellaea glabella, commonly known as smooth Cliffbrake Ferns.

The Smooth Cliffbrake fern is a small evergreen fern with fronds reaching 2 to 8 inches long.  The Smooth Cliffbrake fern is native to the US and parts of Canada.  True to its name, these ferns are commonly found on limestone cliffs and ledges.  A rather rare species, the Smooth Cliffbrake is also considered endangered in Connecticut and Maryland, and is classified as threatened in New York according the USDA.

This just goes to show that sometimes you don't need a fancy set up to have a green wall.  From a mockery stand point, this "green wall" is maintenance free, requires no fertilizer schedule, or irrigation system, and uses exclusively native plants.  Sometimes mother nature just has the best system.

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