Up on the roof tops- green and growing - Portland greenbuilding

Roof top gardens, eco roofs, vegetative roofs, living roofs, green roofs, however they are named theyrefer to the same phenomena; buildings with plants on the roof. As defined by the nonprofit, GreenRoofs for Healthy Cities "A green roof system is an extension of the existing roof which involves ahigh quality water proofing and root repellant system, a drainage system, filter cloth, a lightweightgrowing medium and plants."

Green roofs are growing, in numbers that is. They are becoming a common component ofarchitecture in the urban and rural landscape. Perhaps not as new as we might think, earthen andplanted roofs have been a part natural building practices as long as man has built structures frommud. Sod homes of early settlers in the US, were a common occurrence in the prairie states. Theywere practical, insulative and the mud most readilyavailable.                                                                      SE Portland- Ecoroofs Everywhere

So why the interest in green roofs in our city centers from Chicago to Seattle and now a progressiveincentive program in Portland? As local landscape architect, blogger and designer of several largeprojects, Jason King of Greenworks, PC, states, "The many reasons to install a vegetated roof arethat you are taking something that is purely a functional part of a building and embedding it with arange of multiple benefits - storm water management, habitat creation, insulation and cooling,aesthetics, urban heat island reduction - all while increasing the longevity of the roof and providinggreen space in our cities."

The published data is clear. In dense urban areas aphenomenon called heat island effect occurs.According to the EPA the term "heat island"describes built up areas that are hotter than nearbyrural areas. The annual mean air temperature of acity with 1 million people or more can be 1.8-5.4°F(1-3°C) warmer than its surroundings. In theevening, the difference can be as high as 22°F

(12°C). On hot summer days, the surface temperature of a green roof can be cooler than the airtemperature, whereas the surface of a conventional rooftop can be up to 90°F (50°C) warmer.Installing eco roofs contributes to the reduction of heat island effect while reducing green house gasemissions. Studies have estimated that if all the roofs in a major city were "greened," urbantemperatures could be reduced by as much as 7 degrees Celsius.

Another easily measured benefit of green roofs is the reduction of storm water runoff. Impermeablesurfaces like rooftops discharge untreated water into our watersheds. Often the runoff containspollutants such as mechanical wastes and oil, sediments that clog waterways, bacteria, pesticidesand other chemicals. Eco roofs capture as much as 50% of the runoff as compared to a standardasphalt roof. This means with larger commercial buildings there is often a considerable cost savingsin infrastructure and mechanical construction to capture and treat storm water runoff.

Eco roofs can save in heating and cooling costs. They have been found to dramatically improve aroof's insulation value. A study conducted by Environment Canada found a 26% reduction in summercooling needs and a 26% reduction in winter heat losses when a green roof is used. Green roofs alsoincrease the life expectancy of a roof.

Still not convinced installing a green roof in Portland is cost effective in times of tighter budgets?Currently the City of Portland has initiated an incentive program that will further entice ahomeowner, builder or developer that installing an eco roof is a good investment. Homeowners andbuilding owners are eligible for a maximum 35% discount on their municipal storm water fee forqualifying eco roofs. This initiative was developed to increase sustainable stormwater managementpractices, control non-native, invasive plants, and protect sensitive natural areas. In addition,Portland has created an incentive fund program for up to $5 per square foot of an ecoroof project.Installation costs for eco roofs in Portland range from $5 to $20 per square foot.The deadline tosubmit applications for projects to be considered in the current $5 per sq. foot incentive is Dec, 1st,2009. There are other requirements a project must meet in order to qualify. Those specifics can beviewed on the city's web site.

If you'd like to explore green roofs further the City is hosting a 2-day technical seminar on Nov. 3rdand 4th. There are many examples of green roofs in Portland. Take a photographic tour of someexamples on the City of Portland's web site or visit some of the many individuals and companiespromoting and installing green roofs. One local green roof installation company has the ambitious 5-year goal of Ecoroofs Everywhere and what better way to turn thousands of acres of asphalt intogreen oases.

For more info: www.consult@green-sight.com