Industry gurus BRANZ have endorsed passive ventilation to be a requirement in skillion roof types and also have advised that every one roof forms are passively ventilated as redundancy to eradicate inside moisture. The technique also is effective well with mechanical ventilation systems that aren't externally ventilated i.e they don't http://jaidenzoaxh.ampedpages.com/Considerations-To-Know-About-Roof-Cavity-Ventilation-Systems-23331507