Interview: “Keeping cool roofs bright, white and therefore efficient
Reducing energy consumption is of ever-increasing importance, to which cool roofs can contribute. Can you explain the role of coatings in cool roofs?
Massimo Longoni: Cool roof coatings have high solar reflectance, meaning the roof reflects sunlight and heat away, thus lowering the overall temperature of the building. This results in lower energy consumption during peak hours. By keeping buildings at a lower temperature, cool roofs also reduce the urban heat island effect and decrease the production of associated air pollution and greenhouse gas emissions.
It is important to note that cool roof coatings are not only for new construction. Old roofs can be renovated and converted to cool roofs. Cool roof coatings can also extend the roof’s life indefinitely because it can be recoated when necessary to refresh the surface.
Bleeding is a challenge in roof coatings. How can the binder help to minimise asphalt bleeding?
Longoni: The composition and morphology of “EPS 719” have been optimised to minimise the polymer film’s permeability and consequently reduce the bleed-through of light oil from asphalt and bitumen roofs.
However, flexibility is crucial in exterior roof coating applications and is often associated with low Tg polymers, which tend to be characterised by high free volume in the polymeric film, thus having high permeability and high bleed-through. This resin balances the flexibility while maintaining the bleed-through resistance.
Another crucial issue is dirt pickup. How can this problem be reduced?
Longoni: With time, the performance of a cool roof is a consequence of how clean it stays. The coating must remain white to keep its high solar reflectance. This means, on one side, preventing bleed through to avoid stains and discolorations, and on the other side, to prevent dirt pick up.
Enhanced dirt pickup resistance, exceptional bleed-through resistance, and the right flexibility and adhesion to different roofing substrates are key to keeping cool roofs bright, white and therefore efficient. “EPS 719” was designed to meet all these requirements.