Solar Reflectance Index SRI

Definition: The Solar Reflectance Index SRI serves as a metric for assessing a roofing material’s ability to reflect solar energy while also measuring its capacity to release absorbed heat. It combines two key properties: Solar reflectance measures a surface’s sunlight reflection capability and thermal emittance indicates its capacity to emit absorbed heat. The SRI measurement uses a 0 to 100 scale to represent materials that perform better at deflecting sunlight and minimizing heat retention when they have higher values.

Learn more: What is Zero Net Energy (ZNE)?

Why It Matters

• Energy Efficiency: High SRI value roofs minimize heat absorption which leads to decreased cooling expenses making them perfect for hot regions.
• Urban Heat Island Effect: High-SRI roofs help decrease surrounding temperatures in urban areas while countering the effects of the “heat island” phenomenon.
• LEED Certification: The Solar Reflectance Index (SRI) serves as an essential component for obtaining points in green building certifications such as LEED (Leadership in Energy and Environmental Design).

How It Works

Materials that possess an SRI rating of 100 both deflect solar radiation entirely and release absorbed heat to maintain low temperatures during sunlight exposure.

Materials with an SRI of 0 absorb full solar energy and hold onto it which causes them to heat up substantially.

Examples 

• White Roof Coatings: White Roof Coatings frequently exhibit SRI ratings above 80 which contributes to their high reflectivity and energy efficiency.
• Dark Asphalt Shingles: Dark Asphalt Shingles usually display low SRI ratings between 5 and 15 which causes more heat absorption and higher demands for cooling.

Solar Reflectance Index Applications 

• Cool Roofs: These roofs have high SRI ratings that help them become a standard choice for both commercial buildings and homes to boost energy efficiency.
• Green Building Standards: A growing number of local governments now enforce minimum SRI requirements for roofing materials to advance sustainable building practices.

Fun Fact:

Roofs with high SRI values can decrease their surface temperatures up to 50°F (28°C) more than standard dark roofs when exposed to identical environmental conditions.