Fireworks and Green Roofs
Practically all dry organic materials are combustible at relative low temperatures. Roof shingles or many waterproofing membranes on roofs are typically petroleum-based products (including Asphalt) and they is hardly a difference to dry organic materials. Some products are equipped with chemical fire retardants that could decrease the risk of spreading fire, not the risk of leaks cause by impact.
The living vegetation of functional and well-engineered green roofs contain high moisture contents and most plants (especially succulent plants on large extensive green roofs) have a fraction of the energetic potential comparing to all other components used in a building. The green roof growing media (soil for the green roof plants) is a blend of different mineral components with an organic content of typically less that 15%. It is practically impossible to set this material on fire – not even considering the natural moisture content.
Many fires or leaks on roofs caused by consumer or display fireworks could have been prevented if the building would have had a fully functional green roof or a well-maintained conventional roof (regular removing of organic debris from the roof and gutters).
A fire is the worst-case scenario; however in most cases smoldering firework parts (and cigarettes) are causing leaks on unprotected roofs that are discovered much later. These problems are unknown on functional green roofs. When a green roof prevents a leak or even a fire it is typically not recognized but the payback is right there.
Nature is (literally) so cool.