More and more,
homeowners are seeking out energy-saving building materials for their
renovations and new homes, products that not only secure and improve
structures but also provide long-term cost-cutting on energy bills while
promoting environmental and economic sustainability in the greater
community. Among the array of possible upgrades, “cool metal roofing” easily
answers this consumer demand offering a solid, attractive roofing solution
available in multiple colors, textures, and profiles, for steep-slope and
low-slope applications, that can save your household up to 40% of its annual
energy costs, depending on your geographical region.
The Benefits of Energy
Efficient Metal Roofing As reported by the Cool Metal Roofing Coalition and
the Oak Ridge National Laboratory, installation of reflective metal roofing
can save your home up to 40% in summer cooling energy costs while highly
emissive metal roofs can reduce urban air temperatures by as much as 12 ° F.
Combined, these benefits mean less money out of your wallet, less dependence
on energy resources and less general air pollution in your neighborhood and
across the nation.
The secret to
metal roofing's energy savings is in its variety of finishes. As
shown, the basic, unpainted metal roof will reflect much of the
solar radiation usually absorbed in your attic and home by an
asphalt roof. But, for homes in warmer climates, pre-painted or
granular coated metal roofing systems not only reflect solar energy
but also cool your home by re-emitting most of what solar radiation
Where annual cooling loads dominate, a highly
reflective and highly emissive painted or granular-coated metal roof
is optimal for reducing energy consumption and can actually re-emit
up to 90% of absorbed solar radiation.
metal roofing, including standing seam, is composed of recycled material and
can be installed directly onto an existing asphalt roof, reducing landfill
waste and promoting quick installation as well as decades of
environmentally-sound, maintenance-free strength and beauty. On a building
or on a home, the roof has a major impact with the absorption of heat from
sunlight (Solar Radiation). The heat is either reflected into the atmosphere
or absorbed through conduction into the building. Any solar radiation that
is absorbed will heat the roof's surface. The more the solar radiation is
absorbed, the greater the need to find alternative means to dissipate the
That's where emittance
comes into play. Emissivity is measures of the roof's ability to shed
absorbed heat. The roof's design (type, color, elevation) will determine how
the heat is reflected and absorbed heat is emitted. "Cool" coating
technology focuses on reflecting solar radiation (Solar Reflectivity) and
shedding what heat is absorbed away from the surface (Thermal Emittance).
passing of heat through a roof material into the layer in contact directly
beneath the surface.
heating of the air that passes over a hot surface.
Heat Flux- The
amount of energy flowing through any surface.
Coatings colored with conventional pigments tend to absorb
infrared radiation. Replacing conventional pigments with
"cool" pigments (absorb less infrared radiation) can yield
similarly colored coatings with higher solar reflectance.
Mainly, cool coatings lower roof surface temperatures,
reducing the need for cooling energy in conditioned
buildings and making unconditioned buildings more
do the "cool" pigments work
Pigments provide color by absorbing and reflecting different
parts of the sun's wavelength spectrum based on their
chemistry. Color pigments selectively absorb visible light,
and what light it reflects appears to the human eye as
Pigments also have IR characteristics. While nearly 40% of
the sun's energy occurs in the visible light range (400 to
700 nm), more than 50% of the sun's energy is in the
non-visible infrared region (700-2500nm). It's infrared (IR)
that is largely responsible for heat build-up.
Lawrence Berkley National Laboratory