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Why Cool Metal Roofs are way Cool?
A cool metal roof
reflects and emits the sun’s energy as light back to
the sky instead
of allowing it to enter the building below as heat.
In many climate zones, a cool metal roof can substantially
reduce the cooling load of the building, providing
several direct benefits to the building owner and
occupants:
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increased occupant comfort, especially during
hot summer months
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reduced air conditioning use, resulting in
energy savings typically of 10-30%1,
and
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decreased roof maintenance costs due to longer
roof life.
In addition to these well known benefits to the
building owner, cool metal roofs benefit the environment
and public health in far more ways. As recognition
of these benefits has become more widespread, cool
metal roof requirements are appearing in building energy
codes and green building programs across the nation.
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 Cool
metal roofs directly reduce green house gas emissions by
conserving electricity for air conditioning
therefore emitting less CO2 from power plants. Cool
metal roofs also cool the world independently of avoided
carbon emissions, simply by reflecting the sun’s
energy as light back to the atmosphere, thereby
mitigating global warming. A Lawrence Berkeley
National Laboratory study found that world-wide
reflective roofing will produce a global cooling
effect equivalent to offsetting 24 gigatons of CO2
over the lifetime of the roofs. This equates to $600
billion in savings from CO2 emissions reduction.2
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Climate Change
Mitigation
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 Cities
can be 2° to 8°F warmer than surrounding areas due
to dark materials, including roofs, which absorb the
sun’s light energy as heat during the day and
release it at night as heat.3 This phenomenon
removes the opportunity for air to cool down at
night and results in higher temperatures being
maintained longer. By immediately reflecting solar
radiation back into the atmosphere and reemitting
some portion of it as infrared light, cool metal roofs
result in cooler air temperatures for the
surrounding urban environment during hot summer
months.
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Urban Heat
Island Mitigation
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 Cool
metal roofs, through mitigation of the urban heat island
effect and reduction of ambient air temperatures, in
turn improve air quality. Smog is created by
photochemical reactions of air pollutants and these
reactions increase at higher temperatures.
Therefore, by reducing the air temperature, cool
metal roofs decrease the rate of smog formation.
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Reduced Smog
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Lower ambient air
temperatures and the subsequent improved air quality
also result in a reduction in heat-related and
smog-related health issues, including heat stroke
and asthma.
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Public Health
Benefits
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 Because
cool metal roofs reduce air-conditioning use during the
day’s hottest periods, the associated energy savings
occur when the demand for electricity is at its
peak. Therefore, use of cool roofs reduces the
stress on the energy grid during hot summer months
and helps avoid shortages that can cause blackouts
or brownouts. In addition, for building owners that
pay for their energy based on the time of use, they
save energy when it is at its most expensive – and
hence, save more money!
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Peak Energy
Savings and Grid
Stability |
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 Cool
metal roofs directly reduce the air conditioning use for
buildings by reducing heat gain in the building
below, but they also indirectly reduce air
conditioning use in urban areas by helping lower
ambient air temperatures. Therefore, with cooler
daytime temperatures, buildings and vehicles use
less air conditioning and save additional energy. In
turn, this results in a reduction in the CO2
emissions from electricity generating power plants. |
Secondary Energy
Benefits |
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What
Are Solar Infrared-Reflective Pigments ?
 Global
Warming and its effect on our planet has become an
International issue. We in industry have an opportunity to
participate in the reduction of global warming via the
application of some of the latest technology to “color” our
world in applications such as roofing, sidewalls and other
exterior applications. Researchers in pigment technology
have developed a new classification of pigments that are not
only extremely durable, weather resistant and color-fast,
but also possess a new property - “Solar”, or “Infrared”
Reflectivity. This article will discuss this new class of
pigments, what they are, the history of the technology, and
the features and benefits of their use.
Solar Energy
Well, exactly what are Solar Infrared
Reflecting Pigments? To answer this we must first examine
what Solar Energy is. Solar Energy, or “electromagnetic
radiation” from the sun, consists of radiation in the
wavelengths from about 250 nanometers (nm) to about 2,500
nanometers.
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Ultra Violet - The
wavelengths less than 400 nm are referred to as the
“Ultraviolet” (UV) region. The UV region contains the
shorter wavelengths of radiation that can cause damage
to our bodies and also causes much of the photo
degradation to paints and polymers.
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Visible Light - The
range of wavelengths between 400 nm to 700 nm is called
the visible region. This region is the area where our
eyes are attuned to see light in all its various colors
and shades.
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Infrared - The final
area from 700 nm to about 2500 nm is called the
“Infrared” region. These longer infrared wavelengths are
invisible to the naked eye, yet contain over half of the
solar energy which strikes the earth.
We can see different colors by selective reflection and
absorption of various wavelengths in the visible region. We
can perceive a color such as a red car, because the
radiation (wavelengths of light) in the red portion of the
cars pigment (approximately in the range of 650 nm) is
reflected back to our eyes, while the rest of the
wavelengths (400 to 650 and above 650) are absorbed by the
pigment. We can’t see above 700 nm which is the infrared
portion of the spectrum, so we really can’t determine what
is going on there by sight. However, we can feel the effects
of this “Infrared Energy”, in the form of Heat! Touch your
asphalt driveway, your conventional asphalt shingled roof,
or your black car which has been out in the sun for a while.
It’s quite Hot!! In fact some roofing products can reach
surface temperatures above 190º F or more. Why is this? It’s
because these materials absorb a large portion of the
infrared (heat) radiation from the sun.
Technology
Development
During the Cold War era scientists began working on pigments
which were designed to be spectrally selective for military
applications. These pigments were designed to mimic natures’
spectral reflectivity, so that man- made objects could not
be observed by sophisticated detection equipment. A good
example of this was to spectrally match leaves and trees so
that military equipment that was painted with these pigments
could not be observed by Infrared detectors while in wooded
areas. The first pigments developed for this application
were green and matched the spectral curve of the chlorophyll
in leaves and grass. It just so happens that leaves and
grasses are quite cool to the touch and are actually quite
“Solar” or “Infrared” Reflective, thus Solar reflective
pigments were born.
The first application of
these pigments was for Military Camouflage coatings. It was
not until the mid 1980’s that commercial applications were
developed out of a need by the vinyl siding industry. It
seemed that darker color vinyl siding could not be used
commercially because as the temperature of dark colored
siding increased, the product sagged on the side of homes.
The vinyl siding industry came to Ferro Corporation and
asked if they could develop a dark color pigment that could
reflect heat and eliminate the distortion problem. Ferro did
just that and Infrared Reflective pigments became a
commercial success. As technology grew, a palette of colors
became available that possessed this High Solar
Reflectivity. Today, these same pigments are used in PVDF
and Silicone Modified Polyester coatings commonly used for
metal roofing applications.
Composition of the
Pigments
Just exactly what are these cool pigments and why are they
beneficial to industry? These Solar Infrared Pigments are
basically synthetic mineral compounds known in the industry
as CICP or Complex Inorganic Color Pigments. They are widely
accepted as being the best quality pigments available. They
are made by reacting mineral compounds together in a
calcination process, where these minerals undergo a solid
state reaction at temperatures up to 2200º F to make new
color compounds. Not all CICP pigments are Solar Reflective
however, and only those pigments designated as “Cool” or
Reflective, possess the desired properties to reflect the
Infrared Solar Radiation desired for today’s applications.
Most CICP pigments possess extremely good durability and are
well suited for exterior applications. They are widely used
in coil coating applications, exterior building products and
roofing. These new products are now in great demand and are
replacing the currently used CICP products.
The Benefit to Cool
Metal Roofing
That being said, why is cool metal roofing so important to
industry? First of all, they are able to reflect much of the
solar infrared radiation away from surfaces and direct it
back out in to space so it does not get absorbed by the
roofs and other applications where it is used. A typical
black pigment such as carbon black, will reflect only about
3-4% of the total solar energy that strikes the surface.
This means it absorbs about 96% of the solar energy which
shines upon it and gets very hot!! In contrast a “Cool”
black pigment in very dark color space can reflect about 25%
of the Solar radiation and thereby remain cooler. How much
cooler will the cool metal roof with these pigmented paint
systems be? Theoretically, for every 1% (0.01) increase in a
roof’s reflectivity the surface temperature could be 0.75ºF
cooler, or for very 10% more reflective a roof surface is,
it could be up to 7.5ºF cooler
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Colourcoil Kool Colour Charts for metal roofs
Colourcoil's flagship high performance
pre-painted steel products, PVF2 SeriesTM
and METALLIC PVF2 SeriesTM, for the
downstream manufacturing of cool metal roofs, now come in a
wide range of cool and exciting solar-reflective colours.
They are Kynar 500® flurocarbon based, giving
metal roofing manufacturers and end-users, building products
with the best colour retention and durability properties the
market has to offer.
Architects, home owners or developers who are thinking of
going green can now specify our flagship products for their
metal roofs with confidence as they comply to Malaysia's GBI
(Green Building Index) as well as U.S ENERGY STAR
requirements. (Solar reflective (SR) and Solar Reflectance
Index (SRI) values are published next to the colour chips in
the colour charts).
Visit our website to learn more about our high performance
pre-painted steel products and how our flagship products for
cool metal roofs can help to reduce energy costs.
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Need more info?
Whether you are an
architect, engineer, developer, house owner or a metal
roofing or wall cladding manufacturer, our marketing team
will be most delighted to discuss with you on your specific
product requirements.
If you wish to make a factory visit, obtain a free brochure
or complete specifications and colour charts, please contact
our courteous and friendly marketing staff by calling the
nearest office or just drop us an email at
info@colourcoil.com.
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