Advancing Cool Roofs with the “whitest paint ever”

Kelsey Kane-Ritsch (kk3395)

1. Sustainability Problem (Energy): Roofs are traditionally dark in color which leads to strong absorption of sunlight. This heats up buildings and the surrounding air, contributing to the urban heat island effect. Heat waves can cause serious thermal stress and death when homes cannot be cooled properly for economic or technological reasons. For example, more than half of the deaths associated with a 2003 extreme heat wave in France occurred in people located within their homes or retirement homes. Additionally, LBNL reports that Americans 65 and older are most impacted by heat waves and spend 81% of their time indoors, thus finding that most adverse health effects associated with heat waves occur inside homes. Hotter buildings also lead to greater demand for air conditioning and increased energy usage. Especially as climate change causes global temperatures to soar, demand for electricity to cool buildings and save lives continues to rise. We often power air conditioning with fossil fuels which releases more pollution into the air and furthers the climate crisis. The World Health Organization estimates that more than 90 percent of the world’s population is already exposed to dangerous levels of air pollution.

2. Solution (Whitest Paint Ever for Cool Roofs): Cool roofs are an affordable and easily deployable means of passively keeping indoor temperatures lower during heat events. Cool roofs are roofs that are designed to have high thermal reflectance and high thermal emittance. A number of cool roof technologies are currently used including sheet coverings, highly reflective tiles or shingles, and reflective paint.

Cool roofs themselves are not a new concept – but the recent breakthrough of white paint with an incredibly high level of solar reflectance is an exciting advancement in the field.

  • A research team at Purdue University developed an “ultra-white” paint that reflects 98% of the sunlight that hits it. For comparison, most paints on the market for cool roofs today only reflect 80-90%.
  • The new paint can cool below ambient temperatures because the heat lost by radiation is greater than the heat gained from the sun. At night, it can keep surfaces 19°F cooler than their ambient surroundings, and at noon with strong sunlight, it can keep surfaces 8°F below surroundings.
  • The team found that if the paint covered a roof area of ~1000 sq ft, it would provide a cooling power of 10 kilowatts, which is more powerful than the AC in most houses.
  • The articles also note the downside of cool roofs and this new paint, which is that cool roofs can slightly increase favorable conditions for the formation of ozone and smog when they reflect more UV light back into the atmosphere. (One study found that widespread adoption of cool roofs in Southern California could result in the region violating federal particulate matter standards two additional days each year.)
Image credit: USDOE


3. Stakeholders:

  • City governments, especially in hot regions, interested in lowering temperatures and facilitating energy savings.
  • Private homeowners without access to AC or who prefer a low cost/low energy alternative.
  • Building owners interested in increased comfort and lower energy bills.
  • Architects and real estate developers interested in incorporating cool roof designs into buildings from the start.

4. Implementation: Implementation of this advanced cool roof technology is particularly urgent in rapidly warming parts of the world with lower levels of AC access (i.e. India). Initial implementation steps could include:

  • Additional research and development to minimize degradation of the paint’s solar reflectance capabilities over time.
  • Background research on regions prone to deadly heat waves and GIS analyses of available roof area.
  • Outreach to local governments to encourage regulatory requirements and support for cool roofs.


2 thoughts on “Advancing Cool Roofs with the “whitest paint ever”

  1. This is very cool! The article says it even works in the winter. In an outdoor test at 43 degrees Fahrenheit, the paint still managed to lower the sample temperature by 18 degrees Fahrenheit.

    I live on the top floor of a building, and the heat kills me in the summer. Time to buy some of this paint!


  2. This is interesting, I have not seen the “whitest” paint but I know that quite a few cities are considering a lightening of their surfaces in certain neighborhoods (I think LA is doing a test pilot for its street surface) and some are experimenting with materials other than paint such as a lighter concrete material for sidewalks. I had not previously read about the ozone interference, however, so this is something that cities should definitely consider before widespread use in marginalized communities, where surface lightening is being proposed as a quicker fix than increasing vegetation and tree shading which could take years to grow. Other side note scientists at MIT in 2019 created the “blackest” material, which potentially could have future applications in increasing solar heat collection?


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