It seems to be the general idea that roof ventilation is only for cooling the roof space in summer this is as far from the truth as pigs can fly, as roof ventilation is just as important in winter and all the other seasons of the year.
With the design of building the modern home today there are many problems being experienced by homeowners and not having natural ventilation in the roof space is one of them.
There is a very serious case for ventilation of the roof space to be mandatory in all new homes however it is not going to happen as long as builders put profits before commonsense.
There is another problem to address whereas different geographical areas and climates are obviously going to be different, for example in far north Queensland it can be 38°C in winter and on the opposite in the far reaches of Tasmania at the same time you could have below zero temperatures with roofs covered in snow, there will be a large range of temperatures and conditions in those areas and in between those locations. So it is possible to have extreme heat conditions in one area and snow in another.
So you see that not one part of the country has the same conditions in all the different geographical locations so do you think all types of ventilators can be used under all types of conditions? The answer is a resounding NO.
You cannot use whirly birds and most protruding roof ventilators in cyclonic areas, you cannot use these ventilators where snow builds up as any protusion ventilator has a good chance of leaking through the flashings from snow loading.
You may say we do not have snow or cyclones? But you do have rain, wind and sometimes high wind, most roof vents that have a flashing can leak and will experience wind-blown rain.
So the point is, you need a ventilator system that is low profile, that does not need a flashing, that becomes part of the roof covering, that will not blow off in high winds, will not leak in driving rain, a ventilator system that interacts within itself with inlets and outlets, a ventilator system that will work for you 24/7 365 days a year, spring, summer, autumn and winter and furthermore will not breakdown and last as long as the roof or longer.
Remember roof ventilation in winter is just as important or possibly more important than summer.