White roof membrane: that's why it stays cooler inside

A flat corrugated iron roof in July is not a nice place to stand. The dark surface absorbs sunlight, and the heat doesn't stay on the roof. It travels down through the structure and into the rooms just below, where it lingers until late into the evening.

Why does a dark roof get so hot?

A black surface absorbs almost all the sunlight that hits it. On a clear summer day, a dark corrugated iron roof can reach over 70 degrees, even though the air around it is 25. A white surface does the opposite: it reflects a large part of the light back before it can turn into heat in the corrugated iron.

That's the whole idea behind white roof membrane. Same membrane as the black one, same seal, just in a color that reflects the sun instead of receiving it.

What it means inside

The difference is most noticeable where there is not much between the roof and the head: warehouses, workshops, garages, carports, conservatories, summer houses and allotment houses with flat roofs. If there is neither an attic nor significant insulation, the heat from the roof goes almost directly into the room.

These are also the places where air conditioning is rarely an option. A 400 m² hall cannot be cooled with a split unit, but you can avoid heating it from above.

It solves two things at once

It is worth keeping in mind that the white membrane is not just a color. It is the same silicone-based roofing membrane as the black one, with the same properties:

• Seamless and elastic surface without joints, 100% waterproof
• Up to 40 years lifespan and 25 years product warranty
• Resistant from minus 40 to plus 90 degrees, with reinforced UV protection
• Apply by roller or brush in one coat, directly on top of the existing roof

So you get the sealing and the cooling effect in the same process. The roof needs to be cleaned and sealed anyway, and it doesn't cost extra to choose the color that also keeps the heat out.

Before and after on a corrugated iron roof

This is what a regular corrugated iron roof looks like, before and after.

When does white make the most sense?

White is the obvious choice for flat and low-pitched roofs, where the sun shines almost vertically on the surface most of the day. The same applies to steel and eternit roofs, which conduct heat quickly, and all buildings where people work or sleep directly under the roof.

If, on the other hand, the roof sits over a well-insulated attic space, where the heat doesn't reach down anyway, the color is mostly a question of appearance. Black works just as well there.

How to calculate your own roof

One 20 kg bucket covers up to 13.3 m² in one layer. A roof of 100 m² corresponds to 8 buckets. You can enter your m² on the product page and see the price immediately, without having to do the calculations yourself.

See white roof membrane and calculate the price of your roof