The only absolute certainty is there'll be embers there when there's a bushfire.

It comes down to how many and how big the flame sources are that result from these ember storms.

Ember attack is everything fine that's become airborne that's essentially combustible. So leaves, twigs that are either not burnt yet or are burning and flaming while they fly, or they're glowing while they fly.

They turn up and lodge in and get through gaps and build up in corners and crevices and are continually fanned by the wind, and just create prolific combustible debris build up and localized flame sources on everything external, particularly where there's a complex corner, like everywhere where leaves blow and accumulate in a normal windy day is where these embers and small flame sources build up.

The larger the gaps the more embers and debris get through, and the more large embers get through the probability of ignition happening in that cavity increases.

It's almost impossible to imagine that we could eliminate ember attack at its source by clearing enough vegetation out to many hundreds of meters.

However, solving it from a house design perspective is relatively straightforward.

A house is made up of many gaps, and we need to be really diligent in reviewing where all those gaps may be that embers could enter, and consider what might happen if ignition occurs on the other side of those gaps.

In terms of finding gaps and understanding where they go, it's really a detective process of looking and looking and looking at your house to understand where they are and resolve them through whatever means you can.

It's really an attitude and an approach that you just have to come to terms with, observe very carefully, and look at deliberate vents that may not have small enough apertures. The 2mm rule is absolutely relevant to every gap around your entire house.