Light vs dark coloured roofs

By April 30, 2019 Roofing No Comments

Roof colour – dark or light?

Customers have traditionally preferred lighter coloured roofs in this country, as they are thought to reflect more heat. And the idea is that this would flow on to reduce cooling costs. This has been based on rating systems such as BASIX. However, many councils have restrictions on how light a colour you can use on a roof, which has to do with not creating a clash with the great number of dark roofs already out there.

The belief that lighter coloured roofs will be cooler is founded on fundamental physics – dark coloured surfaces will absorb more heat energy than light coloured ones.

The upshot is that the fastest way to make the biggest difference to cooling through your roof is to paint it in a lighter colour.

However, darker coloured roofs can also perform just as well with reflecting heat, if you use simple strategies like sarking, insulation and ventilation. And many houses in our country, especially newer ones, do have dark coloured roofs, many of them grey or black. So, if your taste runs to dark coloured roofs, don’t despair. Just get canny.

Cooling with darker roofs

Reduce the flow of heat into your home by ensuring that your roof space will resist heat transfer. You can do this by using a double barrier of foil insulation under the roof material and bulk insulation just above the ceiling.

You can also force ventilation into the roof cavity, using a mains or solar powered fan. To keep on top of roof heat transfer, you should aim to ideally be replacing all of the air in the roof cavity every 10 minutes or so. Wind powered fans will likely be inadequate for the job.

Paints and materials for cooling

Then you can choose paints for your roof that will reflect infrared radiation, which is the main component of sunlight that contributes to heating surfaces. While many of these are light in colour, they are available in a wide range of colours including very dark ones.

The choice of material for your roof is also important. You need to choose materials that will re-radiate any absorbed heat back into the sky. Corrugated galvanised iron roofing doesn’t do this very well, unfortunately. The best materials to choose will be both good reflectors and good emitters.

For all advice and services about your roof and for roof inspections, contact Roof Inspection Reports today.