Successful green roof design should consider potential extreme weather events for residential and commercial properties

Taking into account sun studies, potential for drought conditions, extreme rainfall events, wind patterns and extreme wind events. Unlike ground level landscaping – green roofs require special considerations and implementation of thoughtful design that take into account unique weather conditions of an elevated surface such as a roof. Not only should the design phase include structural requirements that spell out saturated weight per square foot, aesthetics, usage; it should also consider the likelihood of high winds, extreme rainfall, and droughts and implement methods to help mitigate damage to the green roof as well as any other part of the building.

A good case as an example of lessons learned is a project in Martha’s Vineyard, MA on Chappaquiddick Island. In October Apex Green Roofs repaired wind damage from 90+mph winds that blew away 7 cubic yards of growth media on a residential green roof.

You can see in aerial images that the gusts blew off green roof material in certain areas.

Image credit – Apex Green Roofs

To remedy this Apex Green Roof installed a wind blanket, (also used for erosion control), secured in place with disc anchors.

Image credit – Apex Green Roofs

What caused these areas to be vulnerable to wind lift is poor plant health in those areas. Essentially bare areas where plants had died off. The standard recommended coverage of healthy plant coverage should always be maintained at 80%. This is why seasonal maintenance is so important. Another contributing factor was that the grasses remaining were in clumps, allowing for some exposed growth media in between.

Apex Green Roofs installed this green roof in 2009. Although our team recommended that a grid with anchor disks would be preferable in this location due to the frequency of high winds – the designer and homeowner did not want to look at the grid during the two-year period it typically takes for plant growth to reach full establishment.