Comments on: There’s No One-size-fits-all Green Roof, Studies Show

By: Ashton

Ashton — Tue, 12 Mar 2013 15:00:20 +0000

This seems to be a trending industry although it does not seem to have taken off so far in the residential areas of London. Prohibitive costs I would imagine.

I certainly hope that it will take off in the future.

By: Polyroof

Polyroof — Wed, 20 Jun 2012 10:44:31 +0000

We agree with the majority of this article and especially the comment that one size does not fit all. This area is still very much in its infancy and while storm water run off is a major issue in some areas there are many more widely accepted reasons for choosing a green roof. For most residential property owners their decision making process is far more geared to the environmentally friendly benefits of the green roof. However, most are put off by the cost, especially if they have a particularly forceful designer or architect.

By: Andrew C. Yanders

Andrew C. Yanders — Wed, 25 Apr 2012 16:12:42 +0000

I also wish to say I am disappointed each of the studies cited were to websites that require you to purchase their papers. So much for the free dissemination of ideas.

By: Andrew C. Yanders

Andrew C. Yanders — Wed, 25 Apr 2012 16:04:37 +0000

For those of us in the green roofing industry, whether design or research, these recent findings come as absolutely no surprise. I learned this in Hort. 101. In 2007, Berghage et al published a paper reporting plants contribute up to 40% of a green roof’s water management capability. http://www.decentralizedwater.org/documents/04-DEC-10SG/04-DEC-10SG.pdf

The plants have always been the star of the show. The whole purpose of the green roof system is to support the plants and provide them with the environment they need to thrive.

Roof tops are an extreme environment; do not be fooled into believing they will ever be able to mimic the surrounding environment. Extensive green roofs should always be designed without irrigation and plants must be able to tolerate drought conditions. Irrigation systems that use potable water are a disgrace. This is why succulents will always be the first choice green roof plant. Extensive green roofs just do not have soil depths deeps enough to support larger-leaf plants that transpire more water. A good green roof designer with years of experience will be able to recommend a larger pallet of plants that include herbaceous wildflowers, but nothing is ever guaranteed when dealing with micro-climates.

As a designer, I always strive to explain to clients the thicker the profile of the green roof system, the more stormwater we will retain and the great the diversity of plants we can establish. This is also why we always specify a granular drainage layer over plastic drainage boards. But 9 times out of 10 we are dealing with structural restrictions and feather weight systems are necessary.

In order to install more green roofs with greater diversity of plants, architects need to add additional structural capacity into their initial roof designs and specify built in place green roof systems based on performance characteristics, not product names. When the average profile of a green roof increases from 3-4 inches to 7-10 inches we will see a proliferation in the types of plants we find on roof tops.