Universal tile ventilators

I had a look at them could only assume they work, problem is cost, my house would need 4 if not 6 and the quote that i got from them was $85 each or supplied and fixed in Canberra $120 each. On the other hand a whirly bird thing is cheaper but you need to have eave vents installed (i would need to cut holes in my asbestos eaves, i have done one and will probably die now). They also make a corrugated vent $120 each or $155 suplied and fixed in canberra, which i want for my shed but 4 for that price it isnt going to happen.

It sounds as if it is exactly as discrete as a more normal unit, but a lot more discreet.