Metal roofing is a long-standing favourite among many homeowners in Australia. Roofs can reach temperatures of just over 60 degrees in the summer and in some regions below 10 degrees in the winter. Without a vent installed, the vast temperature changes cause water to pool, which can damage the infrastructure of your home. The longevity of your home and roof will be diminished and could cost a lot to repair1.
Metal roofs rely on ventilation, specifically static ventilation. Roofs require natural ventilation, rather than relying on fans or other forced methods to create airflow. Static ventilation utilises the natural effects of hot air rising into the roof cavity where moisture and heat are removed4. The air is then cooled and sucked into the roof cavity from outside the house via the eaves to replace it.1
How does ventilation work?
Roof ventilation is the process in which air is circulated through your home to regulate temperature and humidity levels. Hot air rises into your roof cavity and streams into a moisture and extraction system in your chosen ventilator. The air is then cooled and sucked into the roof cavity from outside your home via the eaves to replace it. This simple but effective process controls and maintains the climate within your home and prevents any build-up of moisture due to the vastly different thermal conditions outside and inside the roof cavity.
Another way air can be ventilated in your home is pressure. Wind from outside your home creates different pressures creating a similar type of vacuum, sucking out hot air from inside the roof cavity1.
With two extremes of thermal and wind pressure, they tend to work in the same way for all types of roof ventilation products.
The two types of roof ventilation systems
Passive ventilation requires a natural flow of air to create ventilation in your home. This can be achieved by installing vents in your roof or soffit area5.
Active ventilation uses force to push air through your home and into your roof cavity. This system is most effective in regulating temperature and moisture levels in your home5.
Why is ventilation important for metal roofs?
Ventilation provides your home with warmth in winter and cool air in summer by creating an outlet for moisture and heat to escape. This is one of the most effective and efficient methods to manage your home’s temperature5.
Ventilation is important for roofs as it allows air to flow through the roof cavity and out of your home, allowing the natural system to maintain a mould and mildew-free home5.
Prolong the lifespan of ceiling insulation
Throughout summer, Australians are typically looking for ways to keep their homes comfortable and cool through the long hot months, and this can be achieved by installing ventilation into their roofs. This has the ability to prolong the lifespan of your ceiling insulation and make your home more energy efficient. When the heat has risen to your roof cavity, it can cause your ceiling insulation to break down if there is a build-up. This can lead to costly energy bills and damage your insulation. By installing ventilation in your roof, the heat that naturally rises into the roof cavity will be prevented from building up and prolong the life of your insulation.
Ice dams are formed when hot air rises into the roof cavity in the winter, melting any ice or snow on your roof. Melted ice or snow will flow off your roof and refreeze over your roof’s overhangs, forming ice dams8. For homeowners who live in areas that receive ice and snow in winter, having proper ventilation installed is essential to protect your home.
Ice dams can lead to severe damage to your home by tearing your gutters off, loosening shingles, and creating fluid retention under those shingles that drain into your home. If water cannot properly drain it can seep through insulation, ceilings, walls, and other areas, causing peeling paint, stained and sagging ceilings, warped floors, and mould and mildew8.
Reduce indoor temperature extremes
Indoor temperature extremes are typically when you notice a significant change in the climate of your home when moving from one area to the next. Temperature extremes can be easily avoided by installing roof ventilation. By installing ventilation the hot air that has been trapped in your home can escape while cool air enters back into the space. Installing roof vents can help to prevent overheated attics, which can also impact your energy costs. Through installing proper ventilation your home will be more enjoyable and comfortable throughout the temperature changes each year7.
Laws around ventilation
When installing ventilation it is important to understand the laws and regulations, especially In areas prone to bushfires.
The National Construction Code (NCC) has a guided outline on how to mitigate condensation risk in buildings. In general, the NCC recommends that roofs should be ventilated to reduce the risk of condensation5. Although this is the case, there are some circumstances where homeowners live in dry climates. Insulation may be required to reduce the risk of condensation.
Types of ventilation for metal roofs
Whirlybird roof vents
Whirlybird roof vents are a natural and cost-effective way of keeping your home cooler in the summer months and require little maintenance once installed. By spinning in the wind, airflow is created that removes heat and moisture from the building6.
Ridge ventilation utilises hot air by forcing it to escape through the ridge of the roof, while cool air is drawn through the soffits or eave vents. This helps your property by preventing any mould or build-up of condensation while keeping everything cool. Ridge ventilation can be used on both shingle and metal roofs and are available in a variety of sizes and styles to fit any home.
Solar power roof vent
Solar power is a great way to vent a metal roof. This climate-friendly system keeps your house cooler in the summer and warmer in the winter, and is a cost-effective way of doing so. Through the absorption of the sun, solar panels are charged to vent the air that streams through your home. Solar power ventilation is a great way for any homeowner who is looking to improve their home’s energy efficiency, lower energy costs, and help the environment5.
Gable vents are an effective way to reduce energy costs and improve the comfort of your home. Gable vents are one of the most popular ways to install ventilation onto a metal roof. They allow air to escape the roof cavity, while also allowing fresh air to enter. This is another great way for you to keep your home warm in the winter and cool in the summer5.
How much ventilation is enough for a metal roof?
The amount of ventilation needed for a metal roof will depend on how much roof there is to cover, the type of metal used, and the climate of the region. Typically a home requires two vents, one at the peak of the roof to allow for hot air to escape and one near the eave to allow cold air to enter. If you live in a warmer climate or your roof is significantly larger than the average roof, you may consider adding additional vents5.
- Roof Ventilation, No 1 Roofing & Building Supplies
- February 2020, What does a whirlybird cost to install?, Canstar
- Why roof ventilation is essential, Roof Vents Australia
- Metal roofs need to breathe, Skywalker Roofing
- June 2022, Do you need to vent a metal roof, Vertec Roofing
- Metal roofs vs shingles in hot climates, Great Northern Metal Company
- May 2020, Why roof ventilation is important, Bridger Steel
- The dangers of ice dams to your roof, Brothers Services Company