ventilation in high fire risk areas is always a problem not
because of what is known, but more about what isn't.
can induce fear of the unknown by making various claims to suit
their agenda and most of them work on the ignorance of the mark.
greatest cause of house fires in rural areas is the proximity
of the fire to the house and airborne embers.
do not enter against the flow of a roof ventilator but they
can and do enter via poorly sealed flashings and plastic eaves
vents that cannot resist the onslaught of heat and pressure.
vents used in high fire risk locations should be of perforated
stainless steel material with nominal aperture size of 2mm and
not woven wire which tends to clog up with dust.
this point one prudently errs on the side of caution and as
roof ventilation is essential in maintaining a pressure equilibrium
between internal and ambient, a barrier is employed to offset
any adverse phenomena by way of encapsulation and filtering
any negative flow.
you go running off to stuff mesh into the throat of your roof
ventilator ask yourself 3 questions...
1/ is this going to stop present performance?....
2/ by how much?....
3/ what are other consequences?
the mesh, or screen, employed has a resistance value of 50%
then you've just wiped out 50% of the ventilator performance.
surface area of any screen device used has to be equal to the
open area of the roof ventilator throat therefore the ember
screen should look something like as below