Environment

Coated polymer stack promises to keep your roof cool in summer

Coated polymer stack promises ...
Dr Angus Gentle holding a piece of the special material over an existing cool roof used in testing
Dr Angus Gentle holding a piece of the special material over an existing cool roof used in testing
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Dr Angus Gentle holding a piece of the special material over an existing cool roof used in testing
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Dr Angus Gentle holding a piece of the special material over an existing cool roof used in testing
An infrared image showing the temperature difference between the new surface (center) and an existing cool roof used in testing
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An infrared image showing the temperature difference between the new surface (center) and an existing cool roof used in testing

Of all the scenarios you'd want to find yourself in a heatwave, being barefoot on a hot tin roof would be toward the bottom of the list. These exposed surfaces soak up sunlight to slowly but surely transform into corrugated hotplates, compounding the sweltering ambient temperatures and warming the living space below. But a team of Sydney-based scientists has developed a new material that's claimed capable of keeping a rooftop cooler than the air that surrounds it, saving energy and sweating residents in the process.

Led by Dr Angus Gentle and Professor Geoff Smith from the University of Technology Sydney (UTS), the research team used a mixture of commercially available polyesters and a silver layer to build what it describes as a coated polymer stack. It says these materials could be appropriate for use on basic roofing, and could help mitigate the heating effect that can see roofs rise in temperature by as much as nine to 12 degrees Celsius.

The team says the new material holds promise as it absorbs only three percent of incident sunlight, while also radiating heat at infrared wavelengths. In testing the material, the researchers installed it on top of their faculty's building with no obstructions between it and the sun. When comparing it to a nearby state-of-the-art white roof, they found it stayed 11 degrees Celsius cooler.

"We demonstrate for the first time how to make a roof colder than the air temperature around it, even under the most intense summer conditions," says Professor Smith.

The researchers also wanted to investigate how the material performed once dirt and grime had begun to build up on the surface. They collected data on the performance of both an unblemished surface and one that had been in place for a few days and found that it was able to perform at the same high level regardless of its covering.

The combination of scorching temperatures, concrete structures and bitumen found in city centers, known as the heat island effect, is a problem inspiring many research approaches around the world. In 2012, we saw ETH Zurich researchers roll out a special mat to be placed on roofs, soak up rainwater and then sweat it out when the sun emerges to cool the building underneath. The BioSkin urban facade that coats the 25-story NBF Osaki Building in Tokyo uses traditional Japanese cooling techniques such as water-spraying and bamboo blinds to keep temperatures low.

The UTS team says its solution has the potential to both reduce the heat island effect in urban areas and ease the reliance on air conditioning during hot summer months.

The findings of the study were published in the journal Advanced Science.

Source: University of Technology Sydney

16 comments
watersworm
Industrially feasability to be confirmed, and what price (silver ...) ? But seems very promising and is indeed very smart.
Kevin Ritchey
COOL!
Kevin Ritchey
Now just make it pliable enough to be utilized in spacesuits and my summer clothing.
skremonk
Sounds like a promising concept....... Could it be used to reflect internal heat that is lost through the external walls of a house?
Josh Coray
The silver should be cheap - they use it to make mirrors. This is basically a mirror with a really clever plastic on top. Should be extremely affordable to produce.
Bruce H. Anderson
Several days of accumulation? Since roofs are designed to last years or decades, it would be interesting to see how well it performs after a year of accumulation. And watersworm has a valid concern on industrial/commercial feasability, since the nearby stat-of-the-art white roof has an installed cost that is likely less than us$10/sqft (maybe much less).
StWils
See how well this could work out for India. Along the way toward reflecting it should be achievable and far more useful to concentrate the energy for use as process heat or to generate electricity. Doing that would make this far more useful than simply cooling buildings. Developing nations need off grid electrical power as much as keeping buildings cool. It should be even simpler and therefore cheaper to use the concentrated heat to desalinate water, process sewage or drive heat operated cooling systems along with keeping a building cool.
Douglas Bennett Rogers
Have been holding out for Dow Powerhouse shingles but this may be a better deal. Roof surface would be 30-40 F lower. Wouldn't be good inside. Need foil backed or faced wall board. This is a lot like a NASA paint that consists of a metallic film with a thin white coating, that emits poorly in the mid IR but is highly reflective in the visible.
Don Duncan
In 1987 I coated my hot black composite roof with a reflective white, ceramic impregnated compound. It lowered the temp quite a bit in the triple digit summers of N. CA. I moved 3 years later so I don't know how long the coating lasted, but I doubt it was cost effective. The cost was five times that of white paint. Also, it was quite effective on my metal garage door. If you factor in the fire resistance maybe it was worth it if I had stayed. I have wondered why this did not become widespread in hot climates. Was it due to marketing?
Douglas Bennett Rogers
Was wrong about inside. Would work like aluminum foil but look like paint.