b'FIRE SAFETYAs a result of this research, we now have a greater understanding of how such varied opinions of green roof fire hazards have sprouted.Figure 6: Comparison of HHRs of green roof substrates at dry and Figure 6: Comparison of HHRs of green roof substrates at dry and moist conditions with moist conditions with bitumen membrane: (a) Substrate 1 (dry); (b) Substrate 2 (dry); (c) Substrate 1 (30 per cent of moisture content); bitumen membrane: (a) Substrate 1 (dry); (b) Substrate 2 (dry); (c) Substrate 1 (30 per cent (d) Substrate 2 (30 per cent of moisture content); (e) polymer-modified of moisture content); (d) Substrate 2 (30 per cent of moisture content); (e) polymer-bitumen (PMB) membrane with fire retardants (Bourbigot et al. (2013)).modified bitumen (PMB) membrane with fire retardants (Bourbigot et al. (2013)). Get A Roof Your componentsofgreenroofsagainst regularroofing,theystillallowusto Roofers Proud Of partially understand the fire hazards that such roofs present on a building. From thetestingandnumericalmodelling presented in this article, we can accu-rately state that the thickness and density of the growing media directly impacts the time to failure of a roof deck caused byelevatedtemperatures.Evenmore so,adrygreenroofgrowingmedia of10-cmthicknessefficientlyretards downward heat propagation, even when exposedtosevereheatingloads.A substrate thickness of as little as 3 cm still has a direct impact on the time to failure of a roof deck. It was also estab-lishedthatprotectingawoodenroof deck by a gypsum board is an effective method of reducing fire risks. When it comes to vegetation, mainte-nance is the key to minimizing fire risks, since a well-maintained green roof does notpresentasubstantialamountof additional fuel load. Finally, and maybe most surprisingly, it was established that greenroofscanhaveabetterperfor-manceinfirethanconventionalroof coverings,suchasmodifiedbitumen membrane.Thiswasshownbylower HHR values for the growing medium in dry and moist conditions. This suggests that it is time to revisit regulations that are based on inaccurate fire risk assess-604-882-9734 ments of green roofs and switch to arcabc.org for full member details fact-based regulation that is representa-rcabc.org tive of the actual fire risks a green roof can have.30 lROOFINGBClSPRING 2024'