Ventilation for Flat/Skillion Roofs

Yes, even a well-sealed flat roof can benefit from ventilation. Flat roofs are typically “sealed” on top to prevent water ingress, but the internal cavity can still accumulate heat and moisture. Unless your flat roof is constructed as a “warm roof” (with continuous insulation and a completely air-tight interior layer), some form of ventilation is recommended. Trapped moisture can come from tiny air leaks, or moisture in materials, and without ventilation it has no escape. Providing roof ventilation for flat roofs ensures any hidden dampness dries out and keeps the roof cavity temperature regulated. In short, does a flat roof need ventilation? Almost always, yes – it’s an inexpensive safeguard for the longevity of the roof and the health of the building. Our Vent-A-Roof system will allow even sealed flat roofs to breathe without compromising their water-tightness.

The best way to ventilate a flat roof is to create a path for air to flow in and out. This usually means adding vent openings at opposite sides or levels of the roof space. One common method is to use soffit or eave vents as intakes (bringing cooler outside air in at the roof perimeter) combined with exhaust vents at the roof’s high point (letting hot air out). In practice, for a truly flat roof with parapet walls, this could involve venting through the parapets or at the fascia. The goal is an air circulation cycle: cool dry air in, hot moist air out. With passive ventilation, the warmth and pressure differential do the work once the vents are in place. Vent-A-Roof’s upcoming product simplifies how to ventilate a flat roof by building the intake and exhaust pathway into the structure itself – for example, fresh air can enter under the roof capping and warm air exit through our concealed ridge/apron vent unit – all without external turbines or fans. This means you get efficient flat roof ventilation without altering the appearance of your building.

Skillion roof ventilation follows similar principles to flat roofs. A skillion (or mono-pitch) roof has a higher end and a lower end. In an ideal setup, you’d allow air to enter at the low end (like at the eaves or fascia if possible) and escape near the high end (the top of the slope). Vent-A-Roof’s solution for skillion roofs will likely be installed at that high end – for instance, beneath the barge capping or apex flashing – forming a continuous vent that runs along the top of the roof panel. This vent will let out hot air that gathers at the ceiling’s highest point. It’s always recommended to ensure there is sufficient air from soffit or other intake vents, and the air pathway is clearly planned out. The Vent-A-Roof system is designed to work with these principles in mind, making ventilating a skillion roof straightforward. Our team can advise on the optimal configuration for your specific roof once the product is released.

The National Construction Code (NCC) in Australia doesn’t mandate a one-size-fits-all vent ratio for roofs in all climates, but recent updates have put a spotlight on condensation control, particularly in cooler regions. The code, specifically NCC 10.8.3 and accompanying guidelines, now encourage designers to ventilate roof spaces (including low-pitch and skillion roofs) to mitigate condensation risk. The pitch and length of the building, plus the ceiling design are factors that are taken into consideration to calculate the minimum requirements. This can be achieved with continuous vents (preferred, for consistency) or a combination of individual vents. Vent-A-Roof is commonly used around the country as a method of meeting NCC requirements. Check out our NCC calculator here (link) to see what your structure requires.