Albedo: diagram and definition

When it comes to thermal insulation, there are many ways to optimize a building's performance. Among them is the use of reflective paint to reflect the sun's rays when they hit the roof, thus limiting interior temperature. This act of reflection is defined by a value called the albedo. As shown in our diagram, albedo is the power of a surface to reflect solar energy. The reflective paints used in the cool roof have a high albedo value to maximize the reflection of solar energy.

What is albedo?

Albedo is defined as the reflectivity of a surface. In more explicit terms, it refers to a material's ability to reflect the sun's rays.

Albedo is expressed as a value between 0 and 1. The closer the value is to 1, the greater its reflective capacity. Conversely, a surface with an albedo close to 0 will absorb most of the sun's rays.

In the atmosphere, clouds and mountain tops have a high albedo value. On Earth, ice floes are the closest thing we have to an albedo of 1. The power of the sun's rays is greatly reduced.

How can albedo improve a building's energy performance?

While albedo can be used primarily for scientific purposes, it also has an impact on everyday life. For example, the thermal performance of a building can be greatly improved by adopting a roof with a high albedo value.

A few years ago, the city of Los Angeles decided to paint its roads white, an effective method of reducing urban heat islands thanks to a high albedo.

With this in mind, you can use reflective white paint to limit the effects of heat and optimize the thermal performance of your home or commercial building.

Where to turn for an albedo close to 1?

To use albedo as a lever for thermal optimization, it's worth taking a look at the cool roof. Directly derived from the application of white paint in Los Angeles, the cool roof comes to us from the United States.

This method involves applying reflective white paint to the entire roof of your building. In addition to cooling the interior, the white roof acts as a lever in the fight against global warming.

👉 F ind out how the widespread use of white roofs is influencing the world's climate.

More resources on thermal control through the roof.

Find out more:

• Solar reflectance coefficient (RS) and solar reflectivity index (SRI): what's the difference?