What Is SRI, and Why Does It Decide Cool Roof Performance?
If you’ve compared two roof coatings and noticed one data sheet says “reflectance 0.87” while another says “SRI 109”, you’re not alone in feeling lost. Both numbers describe the same idea from different angles. This post explains the Solar Reflectance Index (SRI) in plain terms, because Panache Green gets asked about it in nearly every specification meeting, and a clear picture saves a lot of back and forth.
The Short Definition
The Solar Reflectance Index (SRI) is a number, usually between 0 and 100, that shows how hot a surface gets under the sun compared with two references. A standard black surface is 0. A standard white one is 100. Some very reflective coatings score above 100, which simply means they run cooler than the white reference. So solar reflectance index explained in one line: it’s a heat-behaviour score, not a colour score.
The Two Ingredients Behind SRI
SRI is calculated from two measured properties, and missing either one leaves the picture incomplete.
- Solar reflectance: the fraction of incoming sunlight that bounces off, on a scale of 0 to 1.
- Thermal emittance: the fraction of absorbed heat the surface radiates away as infrared, also 0 to 1.
Bare polished aluminium reflects well but emits poorly, so it can still run hot. That’s why the thermal emittance of roofs matters as much as reflectance. Most non-metallic coatings sit around 0.85 to 0.90. Panache Green’s Cool Tops Premium reports reflectance of 0.87, emittance of 0.86 and SRI 109.
Why SRI Predicts Real Temperatures
The index comes from a steady-state energy balance under standard sun, wind and air temperature. A surface at SRI 100 typically runs about 20 to 25°C cooler than a black one on a hot afternoon. It’s a model, not a thermometer, but it tracks field data closely enough that codes and rating systems rely on it. That’s the real link between SRI and cool roof performance: higher SRI, lower surface temperature, less heat entering the building.
Initial Versus Aged Values
Here’s where people get tripped up.
Initial values
Measured on a fresh sample. Useful, but flattering.
Aged values
Measured after three years outdoors or accelerated weathering. Dirt, mildew and UV wear can cut reflectance by 10 to 20 points. The Cool Roof Rating Council publishes both.
Compare quotes on aged values. A coating starting at SRI 110 and falling to 70 is not ahead of one that starts at 100 and holds near 90. Panache Green has reported an aged SRI of about 75 after four years on one waterproofing-integrated system, which you can check against site conditions.
Where Codes Use SRI
An SRI rating for cool roofs shows up in several documents, each with its own threshold:
- ECBC (India): roofs under 20 degrees slope need initial reflectance of at least 0.70 and emittance of 0.75.
- IGBC: low-slope roof credits reference SRI of 78 or higher.
- LEED v4: low-slope roofs need initial SRI of 82 or aged SRI of 64.
It’s easy to quote the wrong one, so confirm which version the project follows.
Reading a Data Sheet Sensibly
- Is the SRI computed from tested reflectance and emittance, or just stated?
- Is it initial or aged?
- Which standard was used, such as ASTM E1980, E903 or C1549?
- Did an independent lab test it?
Colour matters too. Darker shades of a cool coating reach lower SRI, which is handy for architects wanting non-white finishes, but numbers should be checked per shade. Panache Green’s Cool Top Xpress pavement range runs from roughly SRI 35 to 102 depending on colour.
What SRI Doesn’t Tell You
It says nothing about insulation, waterproofing or durability. A high-SRI roof with no insulation still transfers some heat, so Panache Green pairs reflective coatings with InsulMix Roof Screed on large RCC projects. SRI is one input into the building envelope, an important one, but still one.
Putting It Together
Think of the Solar Reflectance Index (SRI) as the quickest filter when you’re screening products, and aged test data as the final judge. If a supplier can’t show both, keep looking. Panache Green publishes reflectance, emittance and SRI together, and we’d rather you question the numbers than take them on trust. Specifying by SRI also keeps architects, consultants and facility teams talking about the same measurable thing.
FAQs
For low-slope roofs, 78 or higher is the common IGBC benchmark. Higher is better provided the aged value holds.
Yes. It means the surface runs cooler than the standard white reference.
No. SRI combines reflectance and emittance. Reflectance alone ignores how well heat is released.
Usually, but cool pigments reflect infrared even in darker shades, so a dark cool coating can beat a standard light paint.
Independent bodies such as the Cool Roof Rating Council list tested products. Panache Green is a founding member of CRRC’s wall program from India.
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Client Success Stories
I really appreciate Neetu ma’am and the panache Team for giving us a perfect solution to the heat related problems we experienced.
Before the application of cool tops, the temperature level on the store was 52 ° C, but after the application of Cool tops there seemed a reduction in surface temperature by 4 ° C, the temperature in the area where I sit was 40 °C which has reduced to 37 °C, there is a substantial difference in the ambient temperature, Since last 4-5 months I’m not reducing the temperature of my AC below 28 , Even at 28 I couldn’t keep it for long as the room becomes cooler so I keep for few minutes and turn it off . I really appreciate Neetu ma’am and the panache Team for giving us a perfect solution to the heat related problems we experienced.
The result after applying cool tops from panache is you can see the smiling faces of our team after applying the coating system from panache .
This was an old shed so we had a direct roofing installed, no Insulation. We were very much clear after the discussion with Panache team that we should go for cool Tops coating instead insulation so the result is you can see the smiling faces of our team after applying the coating system from panache #GoGreenwithCoolTops
We took the temperature measurement of outside and inside premises. We noticed a good amount like you can say minimum 6 to 8 Deg C temperature difference.
Looking at the Indian climatic condition during summers, where the temperatures were going too high and whenever it goes up to the peak level, the temperature in the factory shop floor rises affecting the efficiency of the workers. We had a thought in our mind that is there any way to control the temperature, then we came across the Panache company and got in touch with them, after explaining them our problem they came to visit our factory. The team is very committed and technically competent to give us the exact solution for the temperature reduction at the factory. We noticed minimum 6 to 8 °C temperature difference. Thereafter, we received positive feedback from the workers so we decided to go ahead with another project in our office premises. As far as execution is concerned, Panache are experts in this domain. They even contacted us after completion of our installation and ensured that we were satisfied with the workmanship. If someone really wishes to reduce temperature in their premises, I would highly recommend Cool Tops coating from panache – I wish them best of luck for their future projects!
Their prices and services are definitely worth the solution given & treatment done with complete transparency.
I have hired Panache services for the waterproofing & Cooling Treatment on one of the roofs of Parul University premises. Their prices and services are definitely worth the solution given & treatment done with complete transparency. I can definitely recommend them to organizations & people looking for thermal comfort along with waterproofing solutions also.
Totally satisfied by the service received.
I am very impressed by their work on how they provide customized solutions for every problem we have & every task they take up.
The Indoor Temperature has decreased to almost 5 °C. Cool Tops provides Cool Buildings without ACs.
In one of our projects, we had a requirement where AC was not viable and people working under that premises were very much disturbed. To solve that problem, we have consulted Panache for the solution. Panache has provided the full proof solution and after the completion of the Cool Tops Installation, we were much relieved. The indoor temperature has decreased to almost 5 degrees. I could say Cool Tops provide Cool buildings without AC.
The experience for the quality of products with consistency is very appreciable.
I am an engineer & contractor taking turnkey projects. We have used Panache’s various waterproofing products & I recommend Panache's Cool Tops, the special 5 coat system which gives thermal comfort with sustainable performance. The experience for the quality of products with consistency is very appreciable.
I really appreciate their efforts for perfection & sound knowledge of the technology.
We have met the Panache Team from one of our friend’s references who have already taken the services. I must say, they are very professional in what they do. I really appreciate their efforts for perfection & sound knowledge of the technology.
