Green roofs should be designed to provide the necessary fire resistance
The first green roof performance tests, including fire tests, were performed and analysed in the 1990s. It’s pretty safe to say that fire safety regulations differ, sometimes significantly, from country to country. So in order to gain a larger global perspective we need to review the way fire safety is treated and talked about on major green roof markets.
After reviewing many cases over the past few years, we can say that generally green roofs should be designed to provide the necessary resistance to the spread of fire by considering 4 primary measures:
(1) The most cited measure is to increase the content of non-combustibles in the growing medium;
(2) Lower the organic content of the growing medium;
(3) Prevent the system from drying out; extensive roofs are not generally irrigated, therefore the risk of fire is mitigated by creating effective fire breaks and by reducing the organic content of the medium;
(4) Last but not the least, fire safety can also be significantly improved by not employing highly combustible drainage elements (especially at the time of installation).
A number of guidance documents also refer to fire-resistant vegetative systems as “succulent-based” and “grass-based” systems – in both cases the growing media must contain at least 80% inorganic matter.