Many people have been exploring the possibility of installing a green roof, also known as a living roof, on their building. Prior to installation of this type of roof, it is necessary to start with a waterproofing membrane and, if it is to be constantly watered, a drainage system. Note that plants are planted on the roof itself not just in plant containers.

Advantages of a Green Roof

Green roofs, made of sod, have long been in use in foreign countries. The modern green roof is typically made with soil and vegetation which is placed on a traditionally shaped roof. Currently, the U.S. General Services Administration maintains more than 2 million square feet of green roofs on public buildings.

One of the largest green roofs can be found atop the Chicago City Hall. Placed on a flat roof, it consists of 20,000 plants, vines, shrubs and two trees. Many other commercial buildings throughout the nation have installed green roofs which are said to last 50 years. They save a large amount of money on cooling and heating costs for these large buildings. 

In some locations, rooftop ponds have been installed and are considered a green roof. However, this type of roof is not recommended because of evaporation and the possibility of insects, such as mosquitoes, infecting the water.

Some locations have energy tax credits, or other incentives, for people who install green roofs. These incentives may be federal, local or state-sponsored.

Disadvantages of a Green Roof

The weight of green roof vegetation places a heavy weight on the roof’s under-structure. As a result, consideration must be given to replacing all of the supports that hold the roof in place. Often this means that the entire roof must be re-built from scratch and can be very expensive.

Care also must be taken in the selection of plants placed on a roof. Many require maintenance that is not convenient for the average homeowner. The roof must have some type of waterproofing and watering system that will keep the roof green while not damaging the under-structure. In addition, some types of plants attract unwanted pests that can penetrate the house.

It must be remembered that some green roofs require continual weeding and they can be damaged by birds or other insects.

Comparing Green Roofs to Cool Roofs

While green roofs require plants, a cool roof uses roofing material with high reflection properties. These are judged by their thermal emittance (ability to reflect absorbed heat) and a solar reflectance (part of solar energy the roof reflects). 

The Solar Reflectance Index (SRI) is determined when these two values are combined. This SRI ranges from 0 to 100 with a white surface having a value of 100 and a black surface having a value of 0. A cooler roof will reflect a higher SRI.

Advantages of a cool roof includes:

  • Lowers energy bills
  • Increases the life of the roof
  • Reduces the use of air conditioning

Disadvantages of a cool roof includes:

  • Roof reflection can affect neighboring buildings
  • Roof’s Intense reflection can cause masonry joints to over expand
  • Roof equipment may overheat
  • Is not compatible with historic buildings

When considering installing a green or cool roof, it is imperative to talk to a professional roofer who is experienced in this type of roof. They will be able to examine your roof and advise you regarding what changes are involved when changing your roof structure. Serving Connecticut customers since 1977, at Capital Roofing LLC we are proud of our record for providing customers with a wide array of roof choices and expert roofers. If you call us today at (833) 784-5300 we will be happy to discuss our free estimate. You can also fill out our online form at the right of this page or online at

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