Stay Cool with Cool Metal Roofs for Steel Buildings (continuation)

“Cool roofs” are commonly used in steel buildings for commercial and industrial applications. In order to have a better picture of how cool metal roofing for steel buildings work, a clear understanding of the concepts of reflectivity and thermal emissivity is necessary.

Less than 45% of the sun’s energy is visible light. Cool metal roofs for steel buildings use reflective pigment technology in their coatings, which allow them to selectively absorb this visible light and reflect the rest of the light.  Therefore, since a blue pigment will only absorb all wavelengths except those relating to blue, which it reflects, a blue roof looks blue to the naked eye. And a black roof looks black because it absorbs everything.

More than half of the sun’s energy is in the non-visible infrared region. This portion, particularly the near infrared region, is largely responsible for solar-induced heat build-up in steel buildings.

The ability of a roof for steel buildings to transfer the absorbed heat and emit it in the far-infrared region is called emissivity. Cool roofs have high levels of emissivity. This means they radiate the absorbed heat away from the buildings and the surroundings rather than transfer it to the air around the structures.

Cool metal roofing for steel buildings offer a wide variety of color options to choose from, so designers and architects have nothing to worry about.  The pigments not only impart color, they are also durable and long-lasting, with accompanying warranties from fading up to 20 years.

The energy efficiency ability of “cool roofs” has been acknowledged by the different energy and code bodies, including the EPA. Cool metal roofing for steel buildings meet EPA’s energy star reflectivity requirements, which stipulate that roofs must maintain a minimum of 15% reflectivity after three years and 25% Total Solar Reflection for steep-slope roofs.

The benefits of “cool roofs” for steel buildings are summarized below:

• Reduction in building’s heat gain
• Savings in electricity costs due to reduced need for air-conditioning during summer months
• Long roof life expectancy
• Long lifespan for cooling equipment
• Boost in the roof insulation’s thermal efficiency
• Environment-friendly since air pollution and greenhouse emissions are reduced due to reduced use of air-conditioning equipment
• Low maintenance

Although “cool roofs” with dark colors have lesser reflective properties than light-colored ones, they still provide the needed energy savings over other roofing systems for steel buildings.

Source: http://www.coolmetalroofing.org/elements/uploads/news/TMI_CaseStudy_8.pdf

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Stay Cool with Cool Metal Roofs for Steel Buildings

An object’s color significantly affects the level of heat it absorbs once it is exposed to sunlight. In fact, studies have shown that black-colored objects will absorb more heat and become hotter than white-colored ones. This is the reason why people living in tropical climates prefer to wear light-colored clothes, especially whites.

The same is true for roofs of steel buildings. Uncontrolled interior temperatures will most likely be higher for steel buildings with dark-colored roofs.  However, white or any other light color is not the most popular color for roofs among designers, architects and even consumers.

In light of this observation, the metal industry has introduced “cool roofs”, which are coated with colors made from pigments that assist in making the roofs of steel buildings to be minimally affected by solar-induced heating.

Factors that affect the absorption of heat going into steel buildings include the construction of the roof, type of roof material, roof slope and especially color. A hot building, no matter what material it is made of, also radiates heat and warms the air in its surroundings. Imagine the effect of having a large concentration of buildings and the result is called “urban heat island effect”, a phenomenon, which has been observed in cities worldwide. The “heat island effect” is both real and measurable as proven by studies done by the EPA.

The EPA’s Heat Island Reduction Initiative also reported that 70% of the solar energy is absorbed by dark-colored pavements and roofs. More heat going into steel buildings means more energy is needed to keep the interiors comfortable to live and work in. That is why the need for a cooler roof is very desirable. It nor only reduces solar-induced heat but also significantly lessens the need for electricity to power air-conditioning equipment.

In layman’s terms, “cool roofs” for steel buildings minimize the amount of energy absorbed by reflecting most of the sun’s energy.

(to be continued)

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