New trend that breaks up the monotony of common roofs: Green Rooftops

Long popular in Europe, green rooftops have begun to appeal to homeowners, businesses and even cities as an attractive way to promote environmentalism while solving the problems of conventional roofs. Green roofs supplement traditional vegetation without disrupting urban infrastructure -- they take a neglected space and make it useful.

A green roof or living roof is a roof of a building that is partially or completely covered with vegetation and a growing medium, planted over a waterproofing membrane. It may also include additional layers such as a root barrier and drainage and irrigation systems.

Green roofs last longer than conventional roofs, reduce energy costs with natural insulation, create peaceful retreats for people and animals, and absorb storm water, potentially lessening the need for complex and expensive drainage systems. On a wider scale, green roofs improve air quality and help reduce the Urban Heat Island Effect, a condition in which city and suburban developments absorb and trap heat. The layers of a green roof must, like any roof, accommodate drainage and protect the building from the elements with a waterproof membrane. But they also must create a growing area and potentially provide support, irrigation and root protection barriers while staying as light as possible.

"The savings comes from reduced utility costs and even reduced [roof] maintenance over time. But the green roof has to be properly installed and inspected from time to time." (Sarnafil)

Growing plants on your roof provide insulation in the winter and a cooling effect in the summer.

The exact amount of savings is difficult to calculate, as utility costs vary from state to state. But according to the National Research Council of Canada, a green roof can reduce air conditioning demand in the summer by as much as 75%. It should have no more than a 20-degree slope, if not lower.

There are two types of living roofs — extensive and intensive, Glazer explains. Extensive roof gardens are lighter, cheaper and shallower. Intensive gardens are heavier and more expensive. For existing homes, Glazer recommends the extensive roof garden. An exposed roof can get as hot as 158 degrees on a sunny day, while a green, shady roof heats to just 77 degrees, according to the council.

Green roofs do their part for the environment. By lowering air conditioning demand, green roofs decrease production of associated air pollution and greenhouse gas emissions, says the U.S. Environmental Protection Agency.

Another important financial benefit: the reduction in home maintenance costs

They prolong the life of the roof underneath it. They protect the roof from the sun, which can wear down the roof, and from snow and rain. They have been proven to increase the length of roof life. Depending on load capabilities and other application-driven requirements, green roofs can be planted with herbs, grasses, flowers, even trees, in an exciting variety of colors, textures, scents and heights. Patios and walkways can become a useable part of the roof environment. Today it’s clear: vegetated roofs offer many social, environmental and economic benefits.

Key environmental benefits of green roofs:

  • Reduce storm water run-off which, in turn, reduces the stress on urban sewer systems and decreases run-off related pollution of natural waterways

  • Insulating qualities mean reduced energy costs for building owners

  • Air quality improvement – lower rooftop temperatures mean less smog from the “urban heat island effect”

  • Noise pollution reduction – studies show noise levels in a building can be reduced by as much as 40 decibels

  • Extended life of the roof system due to moderated temperature swings that cause a roof system to expand and contract as well as protection from everyday wear and tear.

- See more at: Sarnafil

Plants have been used on roofs for thousands of years, from sod roofs in Europe to the hanging gardens of Babylon. But in the last 50 years this practice has evolved into what are now called green roofs, living roofs or eco-roofs. Green roofs are those that have been planted with specific vegetation using a well-researched sustainable design methodology. They are an exciting new development in the sustainable building movement, and are gaining in popularity across the world.

Benefits of Green Roofs

There are a number of social, economic and environmental benefits to green roofs, including:

  • Increasing home energy efficiency - cooling in summer, insulation in winter

  • Filtering and cleaning toxins from both air and water

  • Reducing carbon dioxide emissions

  • Retaining rainwater before it evaporates, reducing the likelihood of flooding

  • Reducing urban temperatures and associated smog

  • Insulating against sound and noise

  • Preserving and enhancing biodiversity

  • Providing aesthetic appeal and 'green space' recreational opportunities

  • Using recycled materials like aggregates and plastic sheets

The Movement to Green Roofs

Green roofs are a relatively new sector in the construction industry, but have become a widespread feature across Europe. They are most common in Germany, where over 10% of houses now have green roofs, and the industry is growing at 10-15% each year. Because of their environmental benefits, some European countries like Germany have integrated green roofing into their regulations, and many others provide subsidies and incentives to encourage their development and maintenance.

In the UK there has been a lack of government support and guidance on living roofs, which has hindered their uptake. However, green roofs directly address the UK's Sustainable Development agenda and this situation is likely to change as new policies and standards are developed to support their design and construction. Green roofs are set to become an increasingly important option for builders and planners, turning dead and dull places into green, living spaces.

Published by Zachary McGavin