Does roof ventilation work?

Have you got a hot roof? Insulation consistency is what really works. Insulation is King. Non-motorized or motorised roof ventilation can struggle to reduce uninsulated ceiling surfaces by 2 degrees, and a negligible amount of insulated surfaces.
Some people look at these devices for helping the performance of a building in hot weather. But unfortunately it isn't the most effective or cost effective proposition.
In an Australian climate, roof ventilation is not as critical a means for controlling condensation, because our roofs are already quite leaky. Ducting bathroom/kitchen and toilet ventilation directly outside via the soffit or straight through the roof is way better solution of getting rid of condensation if it poses an issue. Fixing insulation coverage is cheap and easy, and has the potential to provide you savings and comfort during hot and cold climates.

https://efficiencymatrix.com/does-roo...

Dr Mark Dewsbury from the School of Architecture & Design, UTAS, has been exploring many issues around energy flows, ventilation and condensation within unconditioned and conditioned rooms and roof spaces of Australian homes. The research has highlighted many myths and anti-science beliefs about roof space thermal dynamics.  
Mark Dewsbury (PhD) | Lecturer & Building Research | School of Architecture & Design| Faculty of Science, Engineering & Technology