How to Properly Raise the Roof: Exploring Green-Roof Systems in Architecture

The concept of the ‘green-roof’ is not recent in origin, but seems to have gained popularity in the last two decades as the impact of our environmental footprint has become increasingly more significant. When you think of ‘green-roof’ you may envision an aerial view of sparsely placed tiny green patches embellishing the skyline of a tangled concrete jungle, but ‘green-roofs’ are not a science limited to urban environments.

Green roof technology has gained exposure in this type of setting due to the lack of vegetation, increased CO2 levels, and high population found in urban areas, but their benefits aren’t limited to only urban-dwelling populations. The pros of green-roof systems include rainwater absorption, providing insulation, creating a habitat for wildlife, decreasing urban air temperatures, which then helps to mitigate the ‘heat island effect’ (increase of human activity in urban areas causes temperature spike), and finally the psychological benefits of having an aesthetically pleasing environment to look at.

There are two types of green-roofs: intensive and extensive. Intensive green roofs are elaborately designed and create a very well thought, manicured roof-top landscape. The intensive green roofs have much more depth, which means they are able to facilitate a sundry of plant types. They have been known to include pathways, mazes, fountains, ponds, and other design features that result in a dramatic, ornate setting. Intensive roofs are much more expensive to install and because they provide opportunity to select from a vast variety of plants, they are also much more difficult to maintain.

Extensive green-roof systems, on the other hand, can be visualized more as a lightweight, thin veneer of vegetation that rests on the surface of a roof. Without the soil-depth that intensive green-roofs can facilitate, extensive green roofs harbor species of plants that have formulated their own mechanisms for adapting to harsh physical environments, such as Alpine plants. Since they are lightweight, extensive green roof systems can accommodate slopes up to 33% and can be fitted to most structures with little or no additional support.

An additional variety of green-roof that has been making headlines lately provides yet another benefit to the list outlined earlier. Some are designing their green-roofs with the intent to cultivate medicinal herbs. By 2018, Montreal, Canada will be home to the largest hospital facility in North America and consequently, will also feature the largest medicinal green-roof in North American as well. The hospital will procure seven different plant beds that will house twice tested medicinal greens. The herbs selected will all have demonstrated measureable capacities to aid in healing various ailments. 

While they all facilitate different ecological environments, the benefits of the three types of green-roofs are virtually the same. If you’re looking for a glamorous, ecologically diverse roof-top terrace and you can accommodate a higher budget, an intensive green roof system may be a viable option. Anyone looking for a low maintenance, low budget selection for a green roof can’t go wrong with an expansive system. Situations that will benefit from growing a green-roof with a specific purpose, like Montreal's new hospital, can take advantage of having instant access to their own supply of healing herbs. No matter which system is utilized, the opportunity to reduce CO2 levels, decrease urban temperatures, help manage storm water, keep your brain happy, and keep your body healthy are all essential reasons to continue integrating green roofs and prioritizing ‘green-design’ throughout architecture and building practices.