Old school external heavy-set canvas blinds may provide radiant heat protection to windows.
Old school external heavy-set canvas blinds During the Canberra Fires. The embers flew in, hit the canvas blinds, and, because of their incline, simply rolled off. And when his fence burned up past his windows, those drawn canvas blinds offered significant radiant heat protection from that adjacent fence fire. And, although they charred very, very slightly so they discolored a little bit, they didn't burn in situ and provide an additional heat load to his windows. And just a word of warning, they’re the old school heavy-set canvas blinds, and the caution there would be that all blind materials probably aren't created equal.
It doesn’t matter how bushfire resistant your home is, it will fail if you store flammable items under it.
In older houses the most commonly used glass types fail at 12kW/m2 (BAL-12.5). What type of glass have you got?
What can you do to improve your windows?
Stored material under houses is a massive issue. The best design houses are simply not designed to handle the types of fuel loads that are possible to store under them. So, don't do it unless the subfloor space is fully enclosed and ember tight to the same standard as your living area.
Plain or normal float glass, the common plain glass, doesn't really stand up to more than around 12kW/m2 of radiant heat before it cracks. Having two layers of this plain glass as a double glazing window itself doesn't necessarily offer significant more protection than single glazing... laminated safety glass, the glass where it's two layers of plain glass with a plastic between it to make it a laminated safety glass, isn't significantly better than plain glass either....toughened glass, can survive 40kW/m2 of radiant heat before it cracks. So using it as a single or double glazed unit is worth considering. For skylights using Georgian wired glass offers protections a well above 40kW/m2
Protect windows with a screen that actually fits flush with the outside of the entire frame, so the screen protects ember entry to the actual timber surface as well. The other one to consider is some novel painting products that provide some degree of combustion protection, spray systems that are dedicated to spraying on that window itself, and shutters are all reasonable options to pursue