We know the physics – so what kind of testing would be appropriate?
There still is no consensus as to what should actually be monitored. Do we simply want to know what part of a vegetated roof will not fly away during a severe storm and hurt someone (safety factor); or do we want to know how much damage will be done to the vegetation (visual factor)? For the purposes of the building / roofing industry, wind up-lift testing should focus on safety measures, which should be our number one priority, so I want to focus on that. Let me just point out the main concerns and try to identify and summarise some of the key points that are making some global consensus on green roof wind up-lift testing such a challenge.
Real life (in-situ) vs. laboratory testing
1. Real life / In-situ testing and monitoring
These tests usually last a long time and are the best as they represent real-life situations in specific geographic / climatic areas. The main drawback, however, is the distinct likelihood that the testing period will not see any extreme wind situations – so the quality of the final test result is questionable. Also, there are so many different green roof & roof designs with their own specific characteristics that real-life testing should not be considered due to the complexity, cost and duration of the process. In my opinion, they should only be used to help confirm lab test results from real-life monitoring.
2. Laboratory testing
Laboratory tests are then (as always) the best option owing to several factors:
– easy to test in extreme situations
– allow us to test many different applications, installations, and types of green roof designs where both time and funds are limited
– are easily standardised globally
There could be some drawbacks as well, as they don’t necessary mimic real life situations, but this is something that needs to be tackled up-front, in the design stage of the test protocols.
Looking into current testing practices, there are two types of lab tests that are mostly widely used by the green roof industry:
a. Negative pressure test
This test protocol comes from the waterproofing / roofing industry. During the test, negative pressure is applied to the roof surface / waterproofing until the waterproofing membrane becomes detached from the base roof surface and is lifted off (sucked away from the surface). The same test protocol can also be applied to the Green Roof System.