# Solar Reflectance

> The fraction of incoming sunlight a surface reflects, from 0 (absorbs all) to 1 (reflects all); also called albedo.

- URL: https://roof.wiki/solar-reflectance/
- Topic: Climate, Hazards & Sustainability
- Also known as: albedo; SR; solar reflectivity
- Regions: Global
- First published: 2026-11-02 · Last reviewed: 2026-11-02
- Cite as: "Solar Reflectance." roof.wiki. https://roof.wiki/solar-reflectance/

## Key facts

- **Scale:** 0 (absorbs all) to 1 (reflects all)
- **Also called:** Albedo
- **ENERGY STAR low-slope (initial / weathered):** At least 0.65 / 0.50

Solar reflectance is the share of incoming solar energy that a surface reflects rather than absorbs. It is expressed on a scale from 0 to 1 (or 0 to 100 percent). A value of 0.05 means the surface reflects 5 percent of sunlight and absorbs the rest; a value of 0.80 means it reflects 80 percent. The term albedo is often used for the same property, particularly at the scale of cities or the planet.

## Why it matters for roofs

Sunlight absorbed by a roof heats it. The US EPA identifies solar reflectance as the most important property for keeping a roof cool. Lawrence Berkeley National Laboratory reports that a white roof reflecting 80 percent of sunlight stays about 31 °C (55 °F) cooler on a summer afternoon than a grey roof reflecting 20 percent.

## Visible and near-infrared light

A large share of solar energy arrives as near-infrared light, which the eye cannot see. This means two roofs of the same visible colour can have very different solar reflectance. "Cool colour" pigments reflect near-infrared strongly, allowing darker-looking roofs, such as brown tile or grey metal, to stay cooler than conventional products of the same shade.

## Initial and aged values

Reflectance declines as roofs collect dirt, soot, algae and biological growth, and as surfaces weather. Rating programs therefore report both an initial value and a value after several years of outdoor exposure. For example, ENERGY STAR criteria for low-slope roofs have used an initial solar reflectance of at least 0.65 and a weathered reflectance of at least 0.50. The Cool Roof Rating Council in the United States publishes measured initial and aged values for many products.

## Typical values

Reflectance varies with product and condition, but in general:

- black membranes and dark shingles are low;
- conventional coloured shingles are low to moderate;
- cool-coloured products are moderate;
- white membranes and coatings are high when new and clean.

## Related measures

Solar reflectance is combined with thermal emittance to calculate the Solar Reflectance Index (SRI), which some codes and green building programs use as a single performance number.

## Sources

1. Cool Roofs — Lawrence Berkeley National Laboratory, Heat Island Group. https://heatisland.lbl.gov/coolscience/cool-roofs
2. Using Cool Roofs to Reduce Heat Islands — US Environmental Protection Agency. https://www.epa.gov/heatislands/using-cool-roofs-reduce-heat-islands
3. Cool roof (reflective surfaces) — Wikipedia. https://en.wikipedia.org/wiki/Cool_roof