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Sustainable Coating Solutions

Garage doors get a boost from Cool Chemistry

Akzo Nobel Guest Column Oct18 Ma

Chicago-based AkzoNobel has supplied high-performance coil coatings to the building products industry for more than 50 years. In that time, we have delivered many sustainable innovations, including Cool Chemistry formulations for energy efficiency. Cool Chemistry technology is often used for metal roofing to lower air conditioning costs, reduce peak energy demand, and help mitigate urban heat island effects. However, Cool Chemistry is not just for roofing. Garage doors also benefit from these special coatings through enhanced appearance, performance and durability.

AkzoNobel offers Cool Chemistry coatings for pre-painted metal. These coatings are specially formulated with solar-reflective pigments to deliver the highest thermal efficiency.

Building owners who seek higher energy efficiency specify Cool Chemistry technology in the materials used in their projects. When applied to metal roofing, these coatings reduce energy demand, resulting in lower energy consumption, as well as cost savings, reduced carbon emissions, and improved air quality. Cool roofing also helps lessen the impact of urban heat islands.

Cool Chemistry coatings are most often used for metal roofing because the surfaces endure direct and intense solar radiation. Vertical applications, such as siding or garage doors, sustain less concentrated solar exposure, but the benefits of thermal efficiency in these applications are significant, nonetheless.

How Cool Chemistry Works

Cool Chemistry coatings are designed to improve the total solar reflectance (TSR) of a substrate. TSR is the percentage of all solar radiation that is reflected immediately from a surface. A surface with high TSR will reflect more radiation and stay cooler. The solar radiation that is not reflected will be absorbed by the surface and converted into heat. This heat then may be emitted in the form of infrared energy. The release of absorbed heat is known as thermal emittance.

When paint is applied to a metal substrate (as with painted coil), that surface becomes a more efficient emitter of heat. In other words, a higher percentage of the absorbed heat will be released on a painted substrate when compared to bare metal and therefore be cooler. Paint color influences thermal efficiency since light colors are more reflective than darker colors. However, Cool Chemistry formulations use special pigmentation that can reflect more radiation, even when darker colors are used.

With decades of experience and expertise in delivering coatings solutions to the building products industry, AkzoNobel is able to apply Cool Chemistry technology to garage doors to improve their appearance, performance and durability.

A Solution for Garage Doors

When solar energy hits the metal surface of a garage door, a portion of that energy is reflected off the surface (TSR), and a portion is absorbed. Once the energy is absorbed, it cannot be further transferred because there is a layer of insulation behind the metal substrate. Thus, the heat is trapped. Seasonal cycles of hot and cold weather cause the metal to thermally expand and contract, and the result is visible bowing of the metal substrate. Intuitively, the incidence and degree of bowing is greater when the surface is painted in darker colors than lighter colors. (Recall that dark colors have a lower TSR, so more heat is absorbed.)

This metal distortion discouraged manufacturers from offering doors in dark colors. If darker colors were offered, manufacturers were forced to mitigate the distortion by fabricating with higher gauge steel, or adding stiffeners and struts to the structure. These resulted in heavier doors, possibly requiring larger springs to lift them. The additional weight also increased operational wear and tear that will shorten the life of the product.

When Cool Chemistry formulations are used, colors like Charcoal, Black, Dark Brown and Hunter Green reflect heat more effectively. Therefore, garage door manufacturers can design and produce dark colored doors with fewer concerns about metal distortion.

The benefits to the garage door manufacturers and building owners are significant. With Cool Chemistry coatings, garage door manufacturers can use the same gauge steel on all light and dark colored doors and eliminate struts and other supports to produce doors that are lighter weight and more cost effective. The doors also operate more reliably and have a longer life. Equally important, Cool Chemistry formulations have expanded the design possibilities for garage doors, allowing for darker colors to be considered to provide distinction and visual impact in the overall design of the garage or building.

Through innovative and high performing products like Cool Chemistry coatings, AkzoNobel brings engineering and design solutions to many markets.


Brent Fletcher is a product manager for metal coatings at Chicago-based AkzoNobel. For more information, email coil.coatings@akzonobel.com.