Go Green.....Chapter 1

Did you lived in a downtown?a place filled with skyscrapers, carpet of roads and pollution. Can you imagine that  world in which we eat, build, and raise our children will green?

why not ? there are several way to make it come true...one of hot topic for this is green roof for building in down town. just look at this picture of chicago city hall before and after applied green roof.

Chicago is using a grant for the US Environmental Protection Agency to study green roofs. A green roof has been planted on the City Hall building. According to the EPA:

Projected total direct electricity savings were 9,272 kilowatt-hours per year, and the corresponding savings in natural gas for heating were 7.372 therms per year. (This calculation compares the base case R-value, or thermal resistance value To definition provided on the glossary page , of 5.9 with the treated roof – garden and insulation – R-value 21.2.)

Green Roof


   Green roofs go by many names that include, but are not limited to, vegetated roofs, garden roofs, eco-roofs, and rooftop gardens.  Regardless of the terminology used, they perform by reducing roof top runoff, which facilitates the removal of pollutant loads.  Precipitation that falls on the green roof is absorbed, filtered, and retained by the soil media.  This in turn is taken up by the plants.  Evapotranspiration, due to the sun’s radiation, draws much of the water from the soil media and plant life.  This greatly reduces, if not eliminates, the amount of stormwater leaving the site.
With the recent popularity of green roofs across the nation, many people assume the technology is new.  In fact, green roofs have been around for thousands of years.  One of the first notable appearances of green roofs occurred in the Hanging Gardens of Babylon around 500 BC.  

 

The site is considered one of the Seven Wonders of the World. There are two types of green roofs: intensive and extensive. Intensive green roofs can accommodate large trees, shrubs, and well maintained gardens. They can be regularly accessed and use is encouraged. The intensive roof garden is designed with a minimum of a foot of soil depth, which can add 80 – 150 pounds per square foot of load to the building structure. The design also includes complex irrigation and drainage systems because annual precipitation can not feed the more intensive plant life. Regular maintenance for an intensive roof garden is required. The extensive green roof is more low key. It can accommodate many kinds of vegetative ground cover and grasses. Plants from the Sedum genus are usually used because they are hardy and colorful. Access and use of the roof by the public is generally restricted for an extensive roof garden. The extensive roof garden is designed with only one to five inches of soil depth, which can add 12 – 50 pounds per square foot (dry weight) depending on soil characteristics and the type of substrate. The design also includes a simple irrigation and drainage system. Maintenance on an extensive roof garden is minimal.


The construction of roof gardens can be difficult, due to the many layers involved. See figure 1 below. The bottom layer is the roof construction. The roof construction must have a waterproofing layer that is durable enough to safeguard the structure over time with minimal maintenance. An example of a commonly used waterproofing agent is a fluid-applied rubberized asphalt waterproofing membrane (Wood 2004). Above the waterproofing layer is the moisture retention protection mat that retains a portion of the precipitation for future plant usage. Contained within the moisture retention protection mat is a root retardant that prevents plant roots from penetrating. Root barriers often contain copper sulfate to retard plant growth (Moran 2004). The next layer is the drainage layer. Various kinds of drainage layers are used by different contractors. Some layers have drainage channels that allow excess precipitation to collect and drain. Others contain small cups that collect excess precipitation that can be absorbed into the soil medium for plant use in the future. The water contained within the cups provides a moist, beneficial subsoil environment for the plants, without allowing fungus or root rot (Wood 2004). Next a filter fabric mat is installed to prevent soil particles from entering the drainage layer.  

 

The final layer consists of the soil medium. Ordinarily, good soil is very heavy due to its high clay content (Wood 2004). Because of the loads already associated with green roofs, lighter soil mediums are required. Soil medium used for green roofs is a combination of shale, pumice, sand, and organic matter. Care must be taken when preparing the soil mixture to prevent the export of pollutants. Mixes with large quantities of compost have been shown to export nitrogen and phosphorus. The USDA-Agricultural Research Service suggests providing the mix with a quality mature compost manufactured using industrial byproducts high in iron and manganese to reduce phosphorus solubility andncrease heavy metal adsorption (Sherman 2005). The mix must promote hydrated plant life, but prevent over-saturation. The depth of the soil medium depends on the type of green roof under construction. 

Green roof implementation provides a wide array of benefits for the user :

• Reduce sewage system loads by assimilating large amounts of rainwater
• Reduce urban heat island effects
• Absorb air pollution, airborne particulates, and store carbon
• Protect underlying roof material by eliminating exposure to the sun’s ultraviolet (UV) radiation and extreme daily temperature fluctuations
• Serve as living environments that provide habitats for birds and other small animals
• Offer an attractive alternative to traditional roofs, addressing growing concerns about urban quality of life
• Reduce noise transfer from the outdoors
• Insulate a building from extreme temperatures

 Some research has shown that green roofs can also provide emotional benefits.  In high stress environments, employees can visit a green roof to take a break from the daily grind.  The relaxing surroundings can improve their health and decrease employee absenteeism, thus making for a happier work environment.  


 Thats all for now, lets start making our world green, this is a guide for green roof. Chicago Green Roof Guide 


Source 


There are plenty way to make our world better. lets save the planet, lets save the earth, lets save our world.


GO GREEN and STOP GLOBAL WARMING .