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Green Roof1

2008 GRHC Award Recipient, Project: California Academy of Sciences, Award Recipient: Rana Creek Living Architecture




2011 is the International Year of Forests. thumb|300px|right|International Year of Forests 2011Trees first appeared on Earth more than 380 million years ago. They take in carbon dioxide and give off an abundance of oxygen. Trees filter, store, and digest pollutants, absorbing water during rainy seasons and giving it back during droughts. In a process known as transpiration, water absorbed by plant roots is given off as water vapor. When the vapor condenses it becomes water, which sustains all life. We have always needed forests and biodiversity. Drawing upon the wisdom of nature, one of the most interesting sustainable landscape features is the living ecoroof, also widely known as a green roof.

The living architecture of green roofs and green walls is a burgeoning industry that offers many environmental advantages, embodying nature’s benefits by returning greenscapes to gray, paved urban environments. thumb|400px|rightThe green roof industry has grown 16% since 2009. Green Roofs for Healthy Cities (GRHC) is a nonprofit organization which was founded in 1999 to promote the industry throughout North America. Their mission is to increase awareness of the economic, social and environmental benefits of green roofs and green walls and other forms of living architecture through education, advocacy, professional development, and celebration of excellence. They are striving to facilitate the changes which will bring these technologies to the forefront of high performance restorative green building design, implementation, and maintenance. http://www.greenroofs.org


Mankind’s Historical Fascination with Green Terraces, Roofs, and Walls

Dating back to the Hanging Gardens of Babylon in the 6th century, humans have long been intrigued by the idea of gardens on roof tops, some even including terraced gardens with waterfalls. Of all the Seven Wonders of the Ancient World, the Hanging Gardens of Babylon excites the imagination the most. http://www.youtube.com/watch?v=-m4wJxWB2w4thumb|300px|rightHow was it possible to build these terraced gardens of ancient Babylon? There are many examples in ancient history of walls built with baked earth and mud, often reinforced with straw or reeds and then compacted with more earth and mud on top. What is certain is that garden roofs and walls require a very strong foundation. Ancient techniques of compacted baked earth and mud could have provided such a structural foundation. thumb|300px|right According to Greek historians, Babylon was the most extraordinary city in the world, controlling water in a desert landscape to maintain the magnificent gardens their emperor had built. The gardens would have utilized plants from an arid environment such as grasses and conifers with thin, needle-like leaves that would have ensured very little water loss. Other plants would have had leathery or waxy leaves to prevent water loss. Gray plants would have reflected the hot desert sun. Plants covered with fine hairs would have reduced the drying effect of the wind and would have trapped the cool night air to keep the plant cool during the day. Historians have recorded lists and lists of the plants of the Hanging Gardens: oak, willow, cedar, lilacs, date palms and orange and lemon trees are a few of the plants mentioned. Though the Hanging Gardens are an historical mirage, they live on in our imagination. Today architects and landscape professionals are combining their knowledge to bring the gardens of Babylon to the reality of the urban landscape.


The Technology of Living Architecture A green roof system incorporates a high quality water proofing and root repellant system, a filter cloth, a lightweight growing medium and plants. They can be modular with prefabricated drainage layers manufactured in movable , interlocking grids, or, each component can be installed separately. The green area on a roof is contained within a perimeter on top of a man-made structure. It can be at below or above grade, but in all cases plants are planted into a growing medium and not the ground.

Principal Green Roof Technology Components

Gr-components

Green Roof Components

Source: National Research Council, Institute for Research in Construction

The market and technology for green roofs is not as well understood in North America as it is in Europe where governments have been very supportive. In Germany, the industry made sales of 700 million DM in 1997, which was an increase of 200 million DM/year in three years. However, North America is coming around and municipalities are beginning to recognize the significant social, economic, and environmental benefits of green roofs.


The Benefits of Green Roofs and Walls

There are many benefits associated with green roofs and walls. They range from economic benefits to community cost savings to improved air quality to stormwater retention and even temperature regulation through the Urban Heat Island Effect. The following benefits reflect what can be expected from a typical urban green roof installation for both the public and for the private investor or corporation.

Public Benefits

Water:

Stormwater Retention and Reduced Runoff Volume

Green Roofs absorb rainwater, keeping it off streets. They can help reduce flash floods as a consequence of intense rainfall events and therefore, reduce the stress on sewage systems during peak flow periods.. Water is stored by the substrate, then taken up by the plants, and then returned to the atmosphere through the process of transpiration and evaporation. In summer, depending on the plants and depth of growing medium, green roofs retain 70-90% of the precipitation that falls on them; in winter they retain between 25-40%. For example, a grass roof with a 4-20 cm (1.6 - 7.9 inches) layer of growing medium can hold 10-15 cm (3.9 - 5.9 inches) of water.

Water Filtration

Green roofs also improve the quality of water harvested from roofs that have been greened because they act as natural filters.

Air Quality:

Filtration of Air Pollutants

Green roofs trap and bioremediate 70% of pollutants that fall on the roof. 1 m2 (10.76 ft2) of grass roof can remove up to 2 kg (4.4 lbs) of airborne particulates from the air every year, depending on foliage type.

Carbon Dioxide/Oxygen Exchange

Through the process of photosynthesis green roofs produce oxygen and sequester carbon by converting carbon dioxide, water, and sunlight into oxygen and glucose. 1.5 m2 (16.15 ft2 ) of uncut grass, produces enough oxygen per year to supply 1 human with their yearly oxygen intake requirement.

Biodiversity:

Provide wildlife habitat, especially when native plants are used. Research in Switzerland and the UK has shown that biodiversity can be enhanced through the use of green roofs, particularly for rare invertibrate populations.

Temperature Regulation:

Moderation of the Heat Island Effect

Green roofs reduce the urban heat island effect (UHI), the overheating of cities caused by large expanses of dark pavement and rooftops which absorb solar radiation and re-radiate it as heat. The Tyndall Centre for Climate Change http://www.tyndall.ac.uk/about recommends a 10% increase in green space in our cities to combat climate change. Green roofs are one technology which can increase urban green space.

Private Benefits

Economic:

Saving on Heating and Cooling Costs

Green Roofs can reduce heating and cooling costs by lowering temperatures inside the building. At the present time, green roofs cannot be given a U-value. However, they do have a thermal performance which reduces the need for air conditioning in the summer as well as providing insulation in the winter. Environment Canada found that a typical one story building with a grass roof and 10 cm (3.9 inches) of growing medium would result in a 25% reduction in summer cooling needs. Karen Liu conducted field experiments in Ottawa, Canada and found that a 6 inch extensive green roof reduced heat gains by 95% and heat losses by 26% compared to a reference roof.

Extended Life of the Roof

Green Roofs increase the life of a roof, providing an economic benefit. It is estimated that green roofs last twice as long as conventional roofs because they protect the roof membrane. This results in decreased maintenance and savings in replacement costs.

Sound Insulation:

The combination of soil, plants, and trapped layers of air within green roof systems act as sound barriers providing sound insulation which can be highly beneficial in an urban environment where noise pollution is caused by traffic, machinery, and airplanes. The offending sound waves are absorbed, reflected, or deflected. Lower sound frequencies are blocked by the growing medium while plants block the higher frequencies. A green roof with a 12 cm (4.7 inches) substrate layer can reduce sound by 40 decibels; a 20 cm (7.9 inches) substrate layer can reduce sound by 46-50 decibels.

Food Production:

Can produce food as well as ornamental plants. the Fairmont Waterfront Hotel in Vancouver has used their roof to grow herbs, flowers, and vegetables on its roof, saving its kitchen $30,000/year in food costs.

Fairmount

Herb Garden on Vancouver's Fairmount Waterfront Hotel

Amenities and Aesthetics:

Improve the quality of life for human users: tranquility, joy, comfort, and enhanced mental health by providing amenity space for day care, meetings, and recreation. They have the potential to improve employee productivity. They also satisfy the aesthetic needs of people looking down upon the roofs from other buildings. The quality of life benefit and aesthetic appeal further increases the value and marketability of the building, particularly for accessible green roofs.


Please note that each installation is different with technical details that vary by region, climate, building, and green roof type and design.

Design & Case Studies in Living Architecture

“Our imagination is the only limit to what we can hope to have in the future“

                                                        Charles F. Kettering 

Living architecture is a synthesis between form and function, a bold step towards cooperating with nature rather than trying to control or alter it. The global community is realizing that our built urban environment requires flexible, multi-functional adaptive solutions.

Earth houses of Peter Vetsch

Earth houses are excellent examples of organic, curvaceous structures which typically blend into a hillside much like the Hobbit homes of J.R.R Tolkien. Using nature as inspiration and a partner in design, earth dwellings are like caves with the earth’s surface as its roof. A Swiss architect by the name of Peter Vetsch became well known for his earth houses in the 70s. However, Vetsch’s basic principle is to avoid removing any earth, shaping the house to preserve the natural environment. Reminiscent of Antoni Gaudi’s architecture, Vetsch turns the box of conventionality on its ear by creating spatial forms without right angles. The technology he uses is sprayed concrete construction to form building shells. Then he covers the houses with earth. The ground serves as an insulating blanket. They are so well insulated that they only use a third of the energy of normal homes in the winter and in the summer they need no temperature regulation.

In fact, his homes have many beneficial features. http://www.erdhaus.ch/main.php?fla=y&lang=en&cont=benefits thumb|400px|right



There are vegetable gardens, sitting areas, and play areas on the tops of the houses. Vetsch emphatically states “What I take from nature I give back.”



Bellevue Youth Theater

A new healthy building project is slated to open in the Spring of 2012 in Bellevue, Washington. It is the 6.2 million Bellevue Youth Theater; it will be nestled into the existing sloped hillside at Crossroads International Park.

4632bellevueBYT w

Bellevue Youth Theater rendering

The 13,000 sq. ft. green roof is being designed by Rana Creek Habitat in California, the same group that designed and installed the green roof for the California Academy of Sciences in 2009. Becker Architects in Bellevue has designed a concrete substrate for the roof of the theater. The green roof will have a waterproofing membrane manufactured by American Hydrotech and a Gardnet soil containment system. It will also have an irrigation system and a perimeter drainage system, and, the materials being used in construction will not contain toxic chemicals. The building will seat 150 indoors and will have a small outdoor stage on the side that opens out from the hill. The slope of the hill will not only reduce rainwater runoff, the hillside green roof will be insulating and therefore, energy efficient. The lawn on the roof will also provide sound attenuation while offering a wonderful place for picnics with a great view of the park.

Sacred Rooftop Sweat Lodge, Firepit, and Medicine Garden in Toronto

The Native Child and Family Services of Toronto renovated a 1980s office building in the heart of downtown Toronto into a sacred space utilizing green roof concepts and technology. The flat desolate roof was reconceived as ceremonial grounds with teaching hills, a working sweat lodge, a fire pit for gatherings, and a sacred medicine garden. The sweat lodge has rusted steel ribs lined with scented Cedar. The firepit is fueled by building code gas rather than firewood. Indigenous plants from the Great Lakes have been used: coniferous and Sumac trees and wildflowers. The medicine garden has Sweet grass, Cedars, sage, and tobacco and corn, beans, and squash are grown in the “Three Sisters Garden.” Rainwater is harvested to water the plants. The sound of a mountain stream can be heard from a fountain on the roof and vines flow over the sides of the roof, purifying the air and providing sound insulation from the busy streets below.

For the native population this green roof is more than practical, it is symbolic of their resolve to be stewards of the natural world, an integral element of their culture. Clients say it makes them proud to be a part of their community. It is very, very positive and provides a sacred space for healing and therapeutic work through ceremony. http://www.nxtbook.com/dawson/greenroofs/lam_2011winter/#/8

The Major Limitations for Implementing Green Roofs

Maintenance Intensive green roofs are park like and therefore need regular maintenance such as weeding, irrigating, and other garden activities. Semi-intensive roofs will need periodic maintenance depending on the plant selection. Extensive green roofs are generally low maintenance, however, they still require some maintenance. For instance, they may still need watering and fertilizing post installation. As long as the drainage elements and the shingle perimeters are kept free of debris and vegetation the building’s integrity will not be adversely affected. A perceived barrier to green roofs is the assumption that the cost of maintenance will be high.

Structure Structural issues can be a barrier to implementation particularly if a roof needs to be retrofitted. Any landscape feature on a roof will have loading implications. The weight of saturated vegetation must be taken into consideration when calculating the structural load.

Guarantees Plant survivability is often a concern and frequently the plants themselves are not guaranteed, only the waterproofing. Guarantees are a very gray area.

Fire Some people may fear that green roofs are more vulnerable to fire. Green Roofs actually protect buildings from fire if the international green roof guidelines are followed for installation. www.fll.de For example, green roofs not to be irrigated can only have 10% combustible material. All shingle perimeters on green roofs must be 500mm to provide a fire break and must be designed into the green roof for large buildings.

Guidance and Support Although most people do not know where to turn if they are interested in learning more about green roofs and walls, a simple internet search will pull up information on Green Roofs for Healthy Cities. GRHC is an excellent source for contractors, architects, homeowners, and businesses. It is only a matter of time before Green Roofs become a commonly accepted form of sustainable water management as well as a viable method of energy conservation.

Policy Perhaps most problematic for smaller communities would be policy-related issues simply because the practice of building green roofs is not very common in the United States. However, as larger cities implement programs and incentives to encourage green roofs, smaller municipalities will likely adopt guidelines for architects and builders.

What is Happening Now?

Training and Credentials

The Green Roof Professional (GRP) designation, a green building credential, was launched in June 2009, establishing a high level of professionalism and multi-disciplinary collaboration. In the last year, more than 350 green building professionals became accredited GRPs through Green Roofs for Healthy Cities (GRHC) [[1]]. These individuals have achieved a high level of knowledge in green roof design, project management, installation, and maintenance. GRHC’s Living Architecture Academy (LAA) provides online learning to meet the needs of the growing green roof industry.

Research

In 2009 Green Roofs for Healthy Cities (GRHC) established green wall performance research at the University of Maryland and the British Columbia Institute of Technology. The Centre for Architectural Ecology at the BC Institute of Technology is located in the School of Construction and the Environment.It is researching the function and performance of extensive green roofs and living walls in the rainforest climate of coastal British Colombia.http://commons.bcit.ca/greenroof/

University of Maryland Leafhouse

University of Maryland Leafhouse

Significant Changes in Policy, Standards, and Incentives

Seattle passed an ordinance in 2007 in the Neighborhood Commercial (NC) zone requiring that all developments have 30% vegetation coverage or its equivalent. Their list of conservation strategies includes large trees, permeable paving, rain gardens, green roofs and green walls. This is provided to architects, landscape architects, and building applicants to assist them in meeting the requirements of the local ordinance. Seattle has also established a weighted system known as the Seattle Green Factor to support green infrastructure implementation. Low water use techniques such as green roofs and walls and rainwater harvesting are given more weight in the Seattle Green Factor.http://www.seattle.gov/dpd/Permits/GreenFactor/Overview/

Toronto enacted the first law in North America in 2010 requiring green roofs on new buildings. Recognizing the benefits of living architecture, other municipalities in North America are also investing in green roofs: New York, District of Colombia, Chicago, Milwaukee, Philadelphia, Toronto, Portland, and Cincinnati.

In 2010, the American National Standards Institute (ANSI) adopted Fire and Wind Uplift design standards developed by Green Roofs for Healthy Cities (GRHC) and the Single Ply Roofing Industry (SPRI).http://www.greenroofs.org/resources/ANSI_SPRI_RP_14_2010_Wind_Design_Standard_for_Vegetative_Roofing_Systems.pdf

The Future? The future of green roofs and walls in North America seems very promising. Large cities such as Seattle have already passed green roof ordinances. Research is being funded at major universities and ANSI standards have been established. Yes, it seems that more and more people in the green building industry will be talking about living architecture and integrating green roofs and walls into their designs for both commercial and residential applications. The Hanging Gardens of modern, urban Babylons may be a reality in the very near future.

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