What is SRI ?
Faced with the challenges of global warming and urban heat islands (UHI), the choice of materials used in large cities plays a very important role. Among the key indicators for measuring their thermal performance, the SRI (Solar Reflectance Index) is now establishing itself as an essential benchmark.
Definition of SRI
The SRI is an index that ranks coatings (paints, plasters, roofs, etc.) according to their ability to resist heating up under solar radiation. It is calculated on the basis of two fundamental measurements: albedo (solar reflectance) and thermal emissivity. The SRI is expressed on a scale of 0 to 100:
– 0 corresponds to a black reference paint, – 100 to a white reference paint (with defined properties: albedo, emissivity, etc.).
Highly reflective materials can have an SRI above 100, while very dark or low-emissivity surfaces (such as certain metals) can have a negative SRI
How is SRI measured?
It is measured on site in order to assess the actual behavior of surfaces in urban conditions. It can also be measured in the laboratory, often on samples, using spectrometry. The method is valid for opaque horizontal surfaces with a slight slope, under standard conditions (sunlight, wind, etc.). A minimum emissivity (>0.1) is required for the measurement to be relevant.
The value of SRI for cities and buildings
SRI allows the ability of coatings to limit urban warming to be compared and serves as a criterion in roofing, facade, or exterior coating projects to reduce the heat effect and improve thermal comfort. It also helps to identify “cool” coatings: light-colored, highly reflective, or high-emissivity.
By encouraging the choice of high-performance materials according to the SRI, we also reduce air conditioning needs, energy consumption, and negative effects on health and comfort.
Conclusion
SRI is now an essential indicator for anyone wishing to build or renovate in a sustainable manner: reducing heat islands, optimizing comfort, and meeting environmental expectations.
At THEMACS Ingénierie, we put our expertise at your service: albedo and emissivity measurements, SRI calculations in the laboratory or on site to help you choose high-performance coatings against heat.
