Green Undressed: Green Roofing - Steel vs Tiles
How do I choose between tiles or steel for my roof?
Your choice of roof will can have a big impact on not only its appearance, but also its sustainability. We weigh up the pros and cons of tiles versus steel.
Roof tiles have been around since before Roman times, so we know they’re durable, and when combined with the correct insulation can help improve a home’s performance. The Romans used terracotta (clay) tiles, which is still a popular choice, although many houses in Australia have cement or even slate roofs.
Popular and available in many styles and colours, concrete tiles are made using Portland cement and aggregate and fired in a kiln. While they are durable, low maintenance and can be recycled at the end of their life, concrete made using Portland cement is the third-largest manmade source of carbon dioxide (see Green Cement article for more information), and concrete tiles’ manufacture produces moderate amounts of embodied energy (40-90 MJ/m2) according to UK-based Green Building Magazine.
Terracotta tiles are manufactured from kaolinite clay with some additives, and then fired at temperatures in excess of 1100°C, with the higher the firing temperature the longer the life of the tile. This results in very high embodied energy of (230-470 MJ/m2), however, like concrete tiles they have a long lifespan, lasting between 30 and 100 years.
Tiles are also a heavy roofing option, which may require structural reinforcement to support their weight.
Steel is a much lighter weight alternative, which can be coated to eliminate rust, and to keep internal temperatures down. Bluescope Steel’s Colorbond roofing products use new technology to reflect more of the sun's heat, leaving the roof space and therefore the building cooler. In hot weather, the company says it can keep uninsulated buildings an average of about 5ºC cooler.
Although their embodied energy is between 180 and 290 MJ/m2, steel is fully recyclable, and steel roofing products have a long life. It has a high strength-to-weight ratio meaning you can have long, column-free spans and lighter structures that use minimal framing material. Less material is required to construct the building, minimising resource use.
Using steel can also reduce the cost and impact of transportation – the more material a truck can carry to a building site, the fewer the total number of deliveries, saving on fuel and GHG emissions.
Many steel structures and building materials can also be prefabricated before site delivery, minimising wastage, and making construction faster and more cost-effective.