Green Roofs

Green Roofs

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Evaluating Green Roof Energy Performance. Sonne, J. 2006. The American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) Journal. 48(2):59-61. (Journal article)

We know that green roofs contribute much less to overflow storm water drainage than do conventional roofs, but how much? Sonne�s study, comparing green roofs to conventional roofs, indicates it could be a good deal. The average maximum green roof temperature in the study proved to be 39�F cooler than the conventional roof. The green roof reduced heat flow through the roof by 70-90%, which in turn reduces cooling costs.

Some figures and tables you might be interested in checking out:

  • Fig. 1: Roof diagram with sensor locations
  • Fig. 2: Building section diagram
  • Fig. 3: Comparison of average roof surface temperatures
  • Fig. 4: Comparison of average roof heat fluxes

Ecoroof. 2006. Portland Online.

This publication is specific to building codes in Portland, Oregon, but can be useful to anyone living in our region. Information ranges from the benefits of ecoroofs to installation in the home. Benefits include reducing runoff, lowering temperature of runoff (which may lead to cooler stream temperatures), increasing vegetation and wildlife habitat, and creating a market for recycled materials such as mulch and compost. Using simple language and descriptive diagrams, the text outlines where ecoroofs can be used and what they cost and look like. Although the immediate cost is more expensive than a conventional roof, it is important to remember that ecoroofs last about four times as long. The article explains important ecoroof criteria, plants to use, and other details such as access and leakage. It also provides a list of contacts with experience in the design and construction of ecoroofs.

Green Roofs from Green Roof Blocks. Green Roof Blocks Homepage.

Ever think that retrofitting your home with a green roof would be daunting or completely out of the question? �The Green Roof Blocks� website introduces visitors to the concept of pre-fabricated green-roof materials something that can make the job much less overwhelming. Green Roof Blocks offers the following features:

  • 2 x 2 ft blocks that easily rest on a rooftop
  • Includes live plants and growth media
  • Simply set them in place and your green roof is complete
  • Ready for shipping anywhere in the U.S. or Canada
  • Priced from $15/sq. ft.

Apparently, most roofs require no additional support to accommodate Green Roof Blocks. Obviously, a qualified contractor is the one to advise you on your particular situation. Green Roof Blocks claims to reduce storm water runoff, improve air quality, and ease the urban heat island effect. Valuable to know!

Green Roofs, Extending Our Environment and Our Industry. Barrett, T. February 2006. The Michigan Landscape. 49(2):23-27. (Magazinearticle)

With over two million square feet of green roofs, Chicago is providing stiff competition with Portland for being one of the �greenest� cities in the country and behind these two cities is the state of Michigan with its green roofs. This is a great little article that defines green roofs, has some photos including a doghouse with a green roof, and it includes a source page for materials and research.

Ecoroof: Questions and Answers. September 2005. Environmental Services. Portland, Oregon.

Published by the City of Portland, this brochure explains that an ecoroof, or green roof, is a lightweight, low maintenance vegetative roof that is used in place of a conventional roof. Green roofs are passive measures of energy conservation because they provide, among other environmental benefits, insulation and lower cooling and heating costs for a home or other buildings. The cost of an ecoroof can be 2-3 times more than a conventional roof. However, green roofs save money in the long run by lasting longer and reducing the rapidly rising heating and cooling expenses.

Components of a green roof are illustrated in a diagram with easy to read explanations. This article also explains operating steps, maintenance, and a plan for replacement of a green roof with lots of great graphics. Visit this site for a few local examples (Portland, Oregon) of green roofs that you can see up close and personal. Resources are provided for local assistance with your ecoroof project, as well as a list of vendors and manufacturers of ecoroof products. Use this informative site as the first step in growing your own green roof!

AUTHORS:

Housing Authority of the City of Milwaukee

809 N. Broadway, Milw, WI 53202

Tony Perez, Secretary-Executive Director

Glen Radford, LEED AP, Housing Construction Supervisor

Milwaukee Metropolitan Sewerage District (MMSD)

260 W. Seeboth Street

Milwaukee, WI 53204

Kevin Shafer, PE, Executive Director

Karen Sands, AICP, Manager of Sustainability

Chris Schultz, Water Quality Sr. Project Manager

When most people think of Milwaukee, Wisconsin, they think of beer. But Milwaukees history as the beer capital of the world is just one illustration of the water-rich history Milwaukee enjoys because of its proximity to Lake Michigan. Looking to its freshwater future without turning its back on the past, Milwaukee is also becoming known as a sustainability showcase. Milwaukees showcase is not just about environmental sustainability though; its also about economic and social sustainability.

Green Roofs

While the seeds of sustainable green infrastructure were first sown here more than 10 years ago, theyve spread nowhere faster than they have across the regions flat rooftops. In fact, the sustainable development model established by the Milwaukee Metropolitan Sewerage District (MMSD) and the Housing Authority of the City of Milwaukee (HACM) features green roofs at its nexus, where water resource enhancements meet not only energy benefits and cost savings, but also environmental justice.

The benefits of green roofs are easily demonstrated in Milwaukee where a small, central portion of the Citys sewer system is a combined stormwater and wastewater system. The vast majority of the City is laced with separate sewer systems. Whether combined or separate, MMSD knows that green infrastructure can play a crucial role in supplementing sewers to manage water a role thats likely to grow if storms continue to intensify as climate change models predict. In addition, HACM knows that green roofs contribute to economic development and good mental and physical health of residents who live in its buildings.

Recognizing this, MMSD has funded green infrastructure projects resulting in nearly two acres of green roofs and HACM has installed over one acre of green roofs. The collective benefit from these roofs that MMSD sees every time it rains is to hold over 55,000 gallons of rainwater that would otherwise pick up pollutants and could flow into area waterways or need to be treated at a water reclamation facility. Simultaneously, the collective benefit HACM provides through green roofs (together with other green amenities) is high-quality living that helps stimulate adjacent economic and social improvements in the City of Milwaukee. Water resource, energy, and quality-of-life benefits go hand-in-hand where Milwaukees green roofs are concerned.

This paper showcases the benefits of green roofs in Milwaukee as they relate to MMSD and HACM. MMSD collects, conveys, stores and treats wastewater and also manages flooding. HACM provides decent/quality, safe and affordable housing with transition options. While both agencies have significantly different focuses, each has come to the independent conclusion that green roofs are good for the City, the water systems it depends on, and the collective region as a whole!

Green roofs are attractive building additions which reduce energy use, storm water runoff, and increase habitat conservation. University of Central Florida research on green roofs includes monitoring pollution, balancing the water budget, and reducing energy use.The Student Union building at the center of campus is the location for a side-by-side 1,600 square foot green roof and a regular flat conventional roof. The plant media is a mixture of Big River Industries gravelite expanded clay, vermiculite, pearlite. and peat moss. The media depth is about 4-6 with under drain. A cistern provides storage for runoff with return irrigation. The native plants are dune sunflower, blanket pinwheel daisy, painted daisy, coral honeysuckle and Simpson’s stopper. Confederate jasmine is also used.

For more information contact Marty Wanielista .

FDEP Press Release: May 5, 2005

CONTACT: Dee Ann Miller, (850) 245-2112 NEW STUDENT UNION EXPANSION TO FEATURE GREEN ROOF —Research is looking up for stormwater management solutions— ORLANDO — The Florida Department of Environmental Protection (DEP) today announced the installation of a 1,600-square foot green roof at the University of Central Florida. While reducing stormwater runoff, the environmentally friendly design could double the life of part of the University’s newly expanded Student Union and cut energy costs by as much as 50 percent.

In January 2004, DEP contracted with the University’s Central Florida Stormwater Management Academy to construct and monitor the green roof as part of a multi-year research project to study low-impact best management practices. Green roofs are an innovative stormwater management solution that can simultaneously improve the energy performance of buildings, air quality and the urban ecology without taking up additional land.

Florida is investing in new ‘green’ technologies to reduce stormwater pollution, conserve energy and protect our rivers, lakes and springs, said DEP Secretary Colleen M. Castille. UCF is leading the way for other universities and businesses to adopt environmentally-friendly practices, which not only protect natural resources but also provide economic and social benefits.

Green roofs use waterproofing and drainage systems that allow a layer of vegetation to grow on flat or sloping roofs. The environmentally-friendly design reduces energy transfer through a roof, decreases stormwater pollutants, and lessens stormwater volume by naturally evaporating the runoff through the plant respiration process.

Researchers are using native plants such as dune sunflower, blanket pinwheel daisy, painted daisy, coral honeysuckle, Simpson’s stopper and Confederate jasmine on the green roof. Plants are grown in four to six inches of gravelite expanded clay, vermiculite, pearlite and peat moss. A drainage system underneath the plants captures and stores runoff in a cistern, which is then reused for irrigation.

The 1,600 square feet green roof was built on a new addition to the University’s student union building. Researchers will monitor the new green roof extension and a section of the existing traditional roof to compare their stormwater and energy characteristics and determine how the roof affects energy consumption and stormwater runoff. Monitoring will begin next month. This is DEP’s second green roof research project. The first green roof was installed a year ago at a Bonita Bay golf course to begin exploring the technology and vegetation that work best in Florida .

For more information about the project please visit www.stormwater.cecs.edu .

Publications and Presentations

Green Roofs at the University of Minnesota’s Landscape Arboretum

Jonathon Hensley

University of Minnesota Graduate Student

The dense, accelerated pace of modern urban development has affected many of the earth’s natural processes. Asphalt and concrete rooftops, roads, and parking lots cover up to seventy percent of land area in dense cities like New York, while open space in sprawling cities like Phoenix, Arizona is lost to development at a rate of 1.2 acres per hour.

Approximately 1.5% of the continental United States, an area roughly equivalent to the state of Ohio, was covered by impervious surfaces in 2004. This percentage continues to grow and can be as high as 75% in urban areas. Of those impervious surfaces (not allowing the permeation of water), roofs can constitute a significant percentage. Such growth in impervious surfaces can result in a variety of environmental impacts including reduced aquifer recharging, overwhelmed storm water systems, urban heating, decreased surface water quality, and increased air ozone and particulate concentrations. These negative environmental effects impact residents and municipalities by affecting clean water availability, storm water and sewage infrastructure costs, decreased runoff water quality, decreased employee productivity, decreased wildlife habitat, and increased operating costs of buildings through increased heating and/or cooling costs. Alternative solutions to traditional impervious building methods are being sought in order to mediate these negative environmental impacts and reestablish the green spaces desperately needed in our metropolitan spaces.

State of Maryland: Dept. of the Environment

Green roofs are becoming an increasingly popular alternative to traditional roofs in metropolitan/suburban areas to reduce the environmental impact of impervious building roofs and to increase green spaces in downtown metropolitan areas. In fact, they are being used to increase green spaces across all areas of commercial development. The above illustration identifies the significant impacts of land development on a local hydrologic cycle; site development substantially increases surface runoff and the removal of tree canopy interception strips away the natural buffering capacities of green spaces- this increase in surface runoff and the removal of green space buffering has had far reaching consequences for our densely populated metropolitan spaces.

The environmental impacts and/or benefits of green roofs in this scenario can include decreased water and nutrient run-off from developed land, reduced ambient air temperature, reduced atmospheric CO2 levels, new garden areas for people and wildlife, and reduced airborne particulates and noise pollution in congested urban environments. Financial benefits can include reduced energy costs for buildings, reduced city infrastructure needs/costs, and improved psychological well-being of citizens resulting in increased productivity among employees. As roofs can account for up to 15-30% of impervious surfaces in cities, the impact of green roofs on the urban environment and citizen well-being can be high.

Extensive Green Roof

Ufa Fabrik, Berlin, Germany

Green roofs can be built in a variety of contemporary styles; the most prominent distinction is between extensive and intensive systems. Intensive green roofs have been used in our country longer than extensive green roofs, but their reliance on deep soil media profiles and irrigation/fertilization to support traditional landscape plants has limited the progress and general utility of this style. By comparison, extensive systems rely on profiles generally not more than six inches in depth and have shown great merit for retrofitting existing buildings that do not have the appropriate structural support for an intensive system.

Extensive green roofs are composed of several material layers designed to protect a building and offer functionality in a metropolitan space. These layers are often composed of waterproofing membranes, a root impermeable layer, a drainage layer, extensive growing media, and vegetation. These systems have been shown in independent studies to positively impact urban/metropolitan environments by re-establishing green biological buffers that mediate storm water runoff, capture particulate pollution, reduce building energy costs for heating and cooling, provide sanctuary for urban wildlife, and improve citizen morale.

For more information on this topic, please see the following references and links:

Dunnett, N. and K. Kingsbury. 2004. Planting green roofs and living walls. Timber Press,

Portland, Oregon. USA.

Snodgrass, E. and L. Snodgrass. 2006. Green roof plants: a resource and planting guide. Timber Press, Portland, Oregon.


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