Green roof basics

A green roof is vegetation growing on a contained roof space.Green roofs help improve the visual appeal and biodiversity of a building while reducing roof temperatures, absorbing rainwater, providing insulation from the elements and noise pollution, reducing the environmental impact of the structure, and creating habitat for native flora and fauna. Once your green roof is in place, it will grow above your expectations.

Benefits of green roofing

The benefits of a green roof are real and wide ranging. Green roofs conserve water by absorbing excess storm water, sometimes by as much as 90% annually, and reduce the effects of storm water runoff. In doing so, green roofs reduce flooding, erosion, artificial heating of water, and they reduce the need for on-site storm water management systems. Succulent green roof plants naturally reduce the risk of fire and the acoustic insulation of a green roof can reduce transmission of outdoor sound by as much as 40 decibels.

The urban heat island effect is the difference in temperature between urban areas and their rural surroundings. Many urban environments have high concentrations of hard, dark surfaces that give off excess heat. Roof surfaces especially can heat up to over 150 degrees Fahrenheit in the summer. Vegetated areas such as yards, parks, and green roofs help to lower the urban air temperature by decreasing temperature differentials between hard surfaces and the air. A fully vegetated green roof will cool the air, which in turn slows air currents, and can reduce the occurrence of dust and violent weather events.

Green roofs can help filter out polluting toxins. The plants and soil act as a substrate that helps settle out and detoxify the pollution. Succulent green plants can help create a meadow-like habitat for butterflies, insects, and songbirds. These same conditions are associated with a number of health benefits for people by decreasing tension and irritability and increasing a sense of health and well-being.


A green roof can provide a welcome respite from the stress of a constructed environment. Even the colors of the plants have been proven to affect mood, with pastels and cool colors like blue, purple and green providing a calming mood, while colors such as red, orange and yellow evoke feelings of warmth and comfort.

A green roof can extend the life of your roof 200-300% by acting as a protective shield from the elements, such as UV radiation, thermal contraction, protection from drying winds, and mechanical damage, which in turn reduces the occurrence of cracks and leaks.

Installation basics

Most green roof projects have the following elements in common: a waterproofing layer, a protection layer, a drainage layer, a separation layer, a soil layer, and plant material.

Waterproofing

The waterproofing layer can be made of various materials. The waterproofing manufacturer must always be consulted before considering any type of green roof system, as most manufacturers will require some type of protection layer if a green roof is installed over their waterproofing layer.

Protective layer

The protection layer shouldn’t hold moisture, such as felt or cloth, and may be made of a material that will inhibit root growth into the roof structure.

Drainage

All green roofs need good drainage, as standing water can potentially cause root rot, and prevent healthy growth of the plants.  Roof drains should be clear, and aggressive root growth needs to be monitored as it could plug drains.  The drainage layer in many types of green roof systems can be made up of a drainage board, rock layer, or a drainage mat.

The separation layer

The separation layer is usually a material separating the soil and drainage area, yet allows water to pass through.

The soil layer

The soil layer contains the medium in which the vegetation is set. This layer provides insulation as well as water storage.

Plant material

A wide variety of plants can be used on green roofs, depending on personal preference and climate.

More detailed information of the variety in construction types and materials will be available on this website shortly. 

To conclude,  in addition to the numerous benefits, a green roof can also increase a sense of pride and civic participation, while at the same time create those beautiful natural views. With today’s emphasis on energy conservation, sustainability, and reduced environmental impact, a green roof is the right thing to do and now is the right time to do it.

Read more on natural building materials here

Read more on natural insulation materials here

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