Cool metal roofing

The choice of roofing material has the greatest impact on the energy conservation of a home. Cool metal roofs coated with Kynar 500® PVDF based resin can reduce energy consumption by up to 40% as part of a total system design (as reported by the Lawrence Berkeley National Laboratory). Kynar 500® coated metal roofing has many attractive features and benefits. The architectural appeal, variety of profiles, texture and color, flexibility and long-term durability make it popular for residential projects.

Kynar 500® based painted metal roofing can achieve solar reflectance of over 70%. Reflected solar energy allows the roof surface to remain cooler, which means less heat is transferred into the building. Cool metal roofing coated with Kynar 500® based resin is one way to limit the urban heat island effect.

Urban Heat Island - a built environment where the large portion of dark absorbing surfaces such as asphalt paving and dark roof tops trap solar energy and radiate the energy back into the atmosphere. Such areas typically have less vegetation than the surroundings. Urban heat islands can have an air temperature that is 6-12°F higher than the rural suburbs.


One way to measure how "cool" is a roof can be with a term called solar reflectance index (SRI). This unitless index is calculated using the solar reflectance value, the thermal emittance value, and a wind coefficient. The SRI calculation can also be used to estimate the surface temperature of the roof product under prescribed conditions. The method for calculating SRI is defined in ASTM E1980-01. Materials with the highest SRI values are the coolest choices for roofing.

A simple SRI calculator is shown below. To calculate SRI, enter the measured solar reflectance value as a decimal, the measured thermal emittance value as a decimal, then click on "Calculate".

Fluorosurfactant Free (FSF®)

Arkema produces Kynar 500® PVDF resin using a patented fluorosurfactant-free (FSF®) process. This means that no fluorosurfactant of any kind is used. Some foreign PVDF producers for the coatings market (who export to the USA and Europe) still reportedly use fluorosurfactants.  It is important for PVDF coating consumers to understand what they are using. 

Kynar 500® PVDF coatings cool metal roofing FAQ

Visit the Kynar 500® PVDF resin based coatings cool metal roofing FAQs page to learn about Kynar 500® coatings for roofing.  Discover why Kynar 500® coatings are the best choice for cool roofing.

What is a cool roof and how does it work?

Cool roofing is defined differently by unique performance criteria established in different codes, standards, and incentive programs. In general, a cool roof is one that does not absorb solar energy which allows the surface temperature to remain lower.

During the daylight hours, a roof is constantly subjected to solar energy striking its surface.  The term “Solar Reflectance” is a measure of the amount of that solar energy that is immediately reflected from the surface. It is not reflected heat, but reflected electromagnetic energy from the sun.  Solar reflectance is reported as a decimal (0 – 1.00) or as a percentage (0-100%).  The solar energy that is not reflected away from the surface is absorbed into the outer surface of the roof product and is converted into heat. The heat can be removed by convection as air flows over the surface, or by conduction through the roof material into the sheathing below. The energy that is left can also be re-emitted to the night sky in the form of infrared energy. That re-emitted energy is referred to as thermal emittance, which is also expressed as a decimal (0 – 1.00) or as a percentage (0-100%).

A cool Kynar 500® based prepainted metal roof can be formulated with special inorganic cool pigments which boost the solar reflectance by reflecting more infrared solar energy. These pigments do not affect the visible color, so that darker colors can now perform like lighter colors in terms of their solar reflectance values.

A cool metal roof with high solar reflectance and high thermal emittance would have a lower surface temperature as compared to a roof with low reflectance and low emittance. In the case of a cool metal roof, a lower surface temperature translates into less heat gain into the attic space or living space below the roof. The result is a cooler building and lower cooling/heating energy usage.

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Why is Kynar 500® the best choice for a cool metal roof coating??

The proven durability of Kynar 500® resin type paint systems allows for stable color and film integrity over decades of exposure. This durability is also seen in the retained amount of initial solar reflectance. Thus, paint systems based on the Kynar 500® resin have a surface that does not retain dirt, remains cool,  and retains its original color better than any other resin type.

In the design and performance of a building, the owner wants to know that the initial energy cost savings projections are maintained over the life of the roof. Most other roof types have been documented to lose some percentage of their initial solar reflectance due to dirt pick up and overall degradation from the weather. In those cases, the aged performance of these cool roofs is far from what the building experiences in the early years. The strong performance of Kynar 500® based paint system which is maintained over time is especially apparent in the retention of the initial solar reflectance of cool Kynar 500® based prepainted paint systems. In research conducted by Oak Ridge National Laboratory on behalf of the Cool Metal Roofing Coalition Kynar 500® based prepainted metal test panels exposed in South Florida were found to retain 95% of their original solar reflectance over more than 30 years. Typically, dirt pick-up and retention is responsible for many roof products’ solar reflectance dropping over time. This is also true for some conventional resins used for prepainted metal roofing. However, Kynar 500® based prepainted metal roofing readily sheds dirt and does not promote the formation of algae or other microbial growth on the surface which could lower the solar reflectance.

Chart 1

In the Metal Construction Association’s roofing certification program, the Kynar 500® based paint systems achieve the highest performance certification – Premium. No other prepainted metal roofing product has the high levels of gloss retention, color and chalk performance that are required for a MCA Certified Premium Painted™ product. So again, the aesthetic appeal of using a Kynar 500 based prepainted cool metal roof is second to none when a building owner is considering what type of cool metal roof to specify.

ARKEMA’s research indicates that there are many reasons why Kynar 500® based paint systems are the product of choice for cool roofing applications.  The most weatherable coatings for metal roofing are based on polyvinylidene difluoride resin technology.  These resins have superior resistance to photo-chemical degradation. They maintain their gloss and color better than any other resin technologies used in today’s exterior paint systems used in the metal roofing industry. Actual exposure of panels in South Florida’s harsh climate after nearly 40 years substantiates the outstanding performance of the Kynar 500® resin.

To achieve superior resistance to weathering, Kynar 500® based paint systems commonly use durable grades of inorganic pigments and tough acrylic resins.  The structure of a Kynar 500® based paint system is thermoplastic in nature, thermodynamically stable and based mainly on the photochemically inert PVDF resin.  This combination has been shown to retain the aesthetic and cool properties of Kynar 500 based paint systems for decades.  This durability is in stark contrast to the common cross-linked binder chemistries used in polyester and silicone modified polyester paint systems often used in the metal construction industry.

TSR Values of PVDF Coatings
  22 Year Florida Panels
Color Lab Retain Washed Unwashed
Black 0.052 0.053 0.047
Green 0.209 0.218 0.210
Blue 0.278 0.271 0.200
Brown 0.471 0.515 0.480
Yellow 0.530 0.538 0.502
White 0.760 0.733 0.688

NOTE: These data were obtained from the ORNL study. TSR values were obtained using a portable solar spectrum reflectometer per ASTM C1549 (D&S Solar spectrum reflectometer model SSR-ER). The device uses a tungsten halogen lamp to illuminate the sample. Four detectors, each fitted with differently colored filters, measure the reflected light in different wavelength ranges. The four signals are weighted in appropriate proportion to yield the solar reflectance.

Source: "Hot Solutions for Cool Roofs", Finishing Today Magazine, February 2007

Other research has found that 70% Kynar 500® based paint systems actually achieve higher solar reflectance when compared to identical colors of polyester and urethane resin based paint systems.

TSR Values of Orange Paints
  22 Year Florida Exposure
Resin Unexposed Washed Unwashed
70% KYNAR 500 PVDF 0.463 0.439 0.426
Polyester 0.375 0.346 0.312
Urethane 0.446 0.436 0.412

Total solar reflectance values of color-matched orange paints based on different resin chemistries before and after 22 years of Florida weathering.


 Source: "Hot Solutions for Cool Roofs", Finishing Today Magazine, February 2007


This significant advantage is in addition to the expected superior retention of gloss and fade, and the prevention of chalking of the paint film.


Hence, a cool Kynar 500® based prepainted metal roof product has the best protection against color fade, chalk and erosion of gloss AS WELL AS having the highest solar reflectance of a color formulated in any other paint resin type. There is no better choice than Kynar 500 resin when selecting a durable exterior paint system for cool metal roofing

What is the ENERGY STAR program?

EPA’s ENERGY STARprogram is familiar to many homeowners who may have noticed the unique label on appliances and electronic equipment. The ENERGY STAR program also has roof products criteria for cool roof products. A roof that meets the ENERGY STAR performance requirements is considered one that is cool and helps to reduce urban heat island effects. The criteria for a labeled roof in the new version 2.0 of ENERGY STAR, starting in October 1, 2007 are:

  • For steep slope applications (greater than 2:12 pitch): initial minimum solar reflectance of 0.25, and 3-year aged minimum solar reflectance of 0.15.
  • For low slope applications (2:12 or less pitch): initial minimum solar reflectance of 0.65 and 3-year aged minimum solar reflectance of 0.50.

Many colors of cool Kynar 500 based prepainted metal roof products can meet these criteria and become labeled ENERY STAR products.

In version 2.0  Energy Star will also require that the thermal emittance value be reported for all roof products. Although no criteria for a minimum value will be required, EPA will collect the emittance data and monitor the situation to determine if an emittance criterion based on climate zone might be applicable in future versions of the program. The surface of the test panels or roofs used to generate the initial and three-year aged data can not be cleaned in any way in version 2.0.

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What is LEED?

“LEED” is an acronym for the US Green Building Council’s Leadership in Energy and Environmental Design rating program. This program comprises a certification rating system for an entire building project, planning, commissioning and produce selection. LEED awards points to those building projects that comply with sustainability standards. Architects, designers and building owners can plan a project in order to acquire points in the program to achieve a level of certification for the building project. There are many LEED programs for different types of building projects. The flagship program, LEED-NC (New Construction), awards points within the following major categories for a project:

  • Sustainable Sites
  • Water efficiency
  • Energy/Atmosphere
  • Materials/Resources
  • Indoor environmental quality
  • Innovation/Design process.

Within each category points are available for compliance with specific design or building practices. A total of 69 points are available if all credits from all categories were to be achieved. LEED designates four level

Certified minimum 26 points

Silver minimum 33 points

Gold minimum 39 points

Platinum minimum 52 points


A cool Kynar 500® based prepainted metal roof can qualify for one point in Credit 7.2 of the Sustainable Sites category if it covers at least 75% of the roof surface area (excluding parapets, skylights and equipment) and meets the following criteria for Solar Reflectance Index (SRI) values:

Low slope (≤ 2:12)  min SRI of 78

Steep slope ( > 2:12) min SRI of 29

Solar Reflectance Index is derived from a calculation in ASTM E1980 which uses a roof’s solar reflectance, thermal emittance and medium wind coefficient to generate a unitless value from 0 to 100. The higher SRI values indicate a roof whose surface temperature is lower, thereby reducing heat gain into the living space beneath the roof.

Most points awarded in the LEED program come from weighted averages of the products, designs or systems used to construct a building.  In essence, a specific building project receives points rather than a unique product. A cool Kynar 500® based prepainted metal roof can contribute to other points in the LEED program due to its recycled content, recyclability and energy efficiency. In the Materials/Resources category, cool Kynar 500® based prepainted metal roofing can account for 2 points by contributing  to the building’s weighted average recycled content. The fact that cool Kynar 500® based prepainted metal is 100% recyclable helps with the construction waste management credit. The use of a cool Kynar 500 based prepainted metal roof can also contribute up to 10 points for the Energy Optimization credit in the category of Energy/Atmosphere.

A growing number of federal, state and local governments are now requiring that the construction of public (and in some cases private) buildings be associated with some minimum level of LEED certification. In many of these cases, the requirement is at least a level of Silver certification. Cities such as Washington DC, Pasadena, CA and Montgomery County, MD are now mandating that ALL new buildings, even those in the private sector, must meet LEED guidelines.

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What should I ask for when selecting a cool metal roof?

A supplier of cool Kynar 500® based prepainted metal roofing products should have either an ENERGY STAR Roof Products label or a product that is listed on the Cool Roof Rating Council directory. These programs certify that the measured cool properties of the product have been substantiated by approved ASTM testing methods. To maximize the energy efficiency, one should ask about the solar reflectance value, and again the higher the better. One should inquire what colors are available in the cool roof category, and which could meet the ENERGY STAR criteria. Depending on where the project is being built, one should ask what the state or local energy code requires for cool roofing, what utility incentives might be available, what state/federal tax credits might be available, and any other rebates, credits, or incentives for which one might be eligible. The warranty of the paint system should be investigated to be sure that a cool Kynar 500® based prepainted product is being offered. Terms for color fade, chalk and film integrity need to be confirmed.

Are there cost savings and financial benefits of using a cool Kynar 500® based prepainted metal roof??

In addition to the direct savings in energy cost, the financial benefits for residential roofing include an increase in the appraised value of the home and a higher resale value. A Kynar 500® based prepainted metal roof is the best investment for a homeowner to make with regard to metal roofing coating. The roof will not depreciate with time and will likely be the last roof installed on the home. The Metal Roofing Alliance refers to this concept as Investment Grade Roofing. Some roof systems begin to depreciate and degrade as soon as they are installed. However, with Kynar 500® based prepainted metal roofing, the proven durability of the coating allows the performance to remain consistent over the life of the roof. In reality, a Kynar 500® based prepainted metal roof appreciates the value of the home rather than depreciates as soon as it is installed.

The cost savings can often be determined using the DOE/ORNL calculator for steep slope roofing energy savings. ( In comparison to a black roof material, this user friendly calculator allows one to compare cooling/heating energy cost savings in any region of the country, varying the level of insulation, the TSR and TE of the roof product, and the local energy costs. Using this tool, one can estimate a relative cost savings for the use of a Kynar 500® based prepainted cool metal roof of various colors and radiative properties.

There are real-world case studies that also demonstrate cool metal roofing’s ability to save money on cooling and heating bills. In 2003, a Georgia school district constructed two identical 90,000 ft2 schools and maintained the thermostats at the district office. The construction of the schools was identical except for the type of prepainted metal installed on the roofs. On one school, a Kynar 500® based prepainted metal roof from Architectural Metal Systems was installed with an Evergreen color (solar reflectance of 0.12) and on the second school, a COOL Kynar 500 based prepainted metal roof was installed with the same color but featuring special pigments in the paint system that increased solar reflectance to 0.29. (paint systems were provided by BASF). After the first year of operation, the school district showed a $8000 savings in cooling/heating utilities at the school with the cool prepainted metal roof.

In another case study conducted in Florida in 2000, Florida Power Light in cooperation with Habitat for Humanity, studied homes with different types of roofs to determine the effect on the electricity cost. Habitat for Humanity built homes of identical size and floor plan with asphalt shingle, barrel tile, terra cotta tile, flat tile and painted metal. The homes were monitored over four months in the summer before they were occupied, and the thermostats were set at 72°F to maintain constant indoor air temperature. The white painted cool metal roof showed a 23% savings in cooling costs compared to the asphalt shingle roof. This was the highest savings of all the roof products tested.

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If you are a residential roof owner or installer what kind of incentives should you know about?

There are many incentives for cool Kynar 500® based prepainted metal roofing used for residential metal roofing installations (in addition to those mentioned above). The Federal Energy Policy Act of 2005 (EPAct 2005) includes provisions  on energy conservation and tax incentives. For renovation of existing residential dwellings, an Energy Star labeled Kynar 500® based prepainted metal roof can qualify the homeowner for up to a $500 tax credit through the end of 2007. For new residential construction, the use of a cool Kynar 500 based prepainted metal roof can help a contractor qualify for a $2000 tax credit per unit built. In this case, the home must be 50% more energy efficient than standards in the IECC 2004 Supplement. The cool Kynar 500® based prepainted metal roof will not itself qualify for the contractor credit, but the benefit of using such a reflective roof product will contribute to the overall home’s energy efficiency.

The EPAct 2005 was designed to expire at the end of 2007, but Congress has already extended certain portions of the original bill until 2009. The new home provisions were extended, but not the renovation provisions. However, several federal bills recently introduced by legislators of the 110th Congress are aimed at extending and improving the EPAct 2005 beyond 2010.

Other incentives from federal and state government agencies are also available for promoting energy efficiency. The Database of State Incentives for Renewables and Efficiency (DSIRE) is a good resource for these types of programs.

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Are there other incentives for using cool Kynar 500® based prepainted metal roofing??

Builders who construct ENERGY STAR Homes can achieve the required level of energy efficiency by using cool Kynar 500® based prepainted metal roofing. A home energy rating service (HERS) scoring system includes a category for cool roofs with TSR criteria that can be met with certain colors and pigment types. The energy rating system is administered by the Residential Energy Services Network (RESNET). RESNET has established a standard for residential and commercial building energy ratings, accredited software programs for aiding in the ratings, and trained raters throughout the country.

The EPA estimates that an ENERGY STAR labeled roof can save homeowners up to 40% in cooling energy costs annually. A study conducted in Florida in cooperation with Habitat for Humanity showed that a white painted metal roof reduced cooling energy by 23%, which was the highest among the types of roof products tested in the study.

The US Green Building Council’s LEED for Homes project is expected to launch in 2007 which will create more of an impetus for builders and homeowners to design the most energy efficient home possible. Cool metal roofing with Kynar 500® based paint systems are expected to be a part of the decision process involved in LEED-H when it comes to the choice of an energy efficient and sustainable roof product.

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If you install roofs in California or Florida, what should you know?

The state utility In Florida, Florida Power and Light, has energy efficiency standards which include criteria for cool roofing. Details of the residential and commercial building programs are contained in the “Residential (and Business) Building Envelope Trade Ally Standards” found on the FPL website at .  In those standards, metal roofing is specifically identified.

Residential customers of FPL can enjoy a rebate when a cool Kynar 500 based prepainted metal roof is installed on a home. The criterion for cool metal roofing in Florida’s rebate program is a minimum solar reflectance of 0.65, entitling the homeowner to a $325 utility rebate.  In addition, only those roof products that are Energy Star labeled or listed on the Cool Roof Rating Council directory are eligible for the rebates. These incentives are balanced against the normal wind uplift and building code requirements for roofing products in Florida, which are some of the most stringent in the entire nation.

The weather in Florida is especially harmful to painted surfaces. A paint system can be degraded by ultraviolet radiation, humidity and heat. Florida has high amounts of all three components. Thus, when specifying a prepainted cool metal roofing product, one must take into consideration of the anticipated degradation of that system under the conditions in that state. Here is where Kynar 500® based prepainted metal roofing products prevail, due to their superior color fade resistance, excellent solar reflectance retention, and gloss retention.

In California, the present 2005 Building Energy Efficiency Standards in their code, commonly known as Title 24, contain strict language on the allowable type of cool roofing for low slope roofs used in non-residential construction. To comply with the code, a cool roof must either meet prescriptive criteria of 0.70 TSR and 0,75 TE (and be listed on the Cool Roof Rating Council directory), or else it can be used if tradeoff calculations are made to modify other building components in order to make up for the non-cool roof.  More information can be found at

The 2008 version of Title 24 will be addressing cool roofing for steep slope residential applications.  The final protocol is expected to be published later in 2007. Several software programs in use by the California Association of Building Energy Consultants (CABEC) help a designer and building owner to determine if their materials and design meet the code. Only very light colors of cool Kynar 500® based prepainted metal roofing would meet the prescriptive requirements in the present state energy code for low slope commercial roofing. In the case of low slope roofing, Kynar 500® based prepainted metal roofing is not common but it is used in some situations.

In California, residential customers of Pacific Gas & Electric (PGE) and Southern California Edison (SCE) are also eligible for rebates when they use a cool roof as defined in the two programs. The climate zones for each program differ due to the customer base for each utility, but in both cases for steep slope roofing a two-tiered rebate structure is in effect.  For cool Kynar 500 based metal roofing with solar reflectance between 0.25 and 0.39 a $0.10/ft2 rebate is offered. For cool Kynar 500® based prepainted metal roofing with solar reflectance greater than 0.40, a $0.20/ft2 rebate is offered.  For low slope roofing products, a cool Kynar 500® based prepainted metal roof with solar reflectance greater than 0.70 would qualify for a $0.20/ft2 rebate.  Depending on the color and type of cool pigments, many Kynar 500® based prepainted metal roof coatings can qualify for rebates in both of these programs.  In both programs, only those roof products that are listed with the Cool Roof Rating Council are eligible.

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Are there codes or standards regulating cool metal roofing?

Practically every state has adopted some version of the International Energy Conservation Code (IECC) as their state energy code. There are some exceptions where unique codes have been established, or where local municipalities’ codes are enforced. The IECC references cool roofing. The Alliance to Save Energy’s website contains state-by-state information on the latest developments in state and regional energy codes.

California has created its own unique energy efficiency standards within their building code, referred to as Title 24.  The 2005 version of Title 24 defines cool roofing with a prescriptive requirement of min solar reflectance of 0.70 and thermal emittance of 0.75. the 2005 version of the code applies to low slope roofing on commercial buildings. A building whose roof does not meet the prescriptive criterion for cool roof, can comply with the energy code using either building component or whole building performance based trade-off provisions. The 2008 version of Title 24 is expected to include cool roof provisions for steep slope and residential roofing. The exact provisions of the 2008 version are not yet known, but the final standards are expected to be complete before the end of 2007.

The city of Chicago has an energy code with provisions for cool roofing in the Urban Heat Island section of its building code. Presently any low slope (≤2:12) roofing project in the city must have a minimum initial solar reflectance of 0.52 and a three-year aged reflectance of 0.40. This performance criterion will change as of September 1, 2008 when the reflectance requirements will match those of the Energy Star program at that time. For moderate slope (2:12 to 5:12) roofing projects, the requirement for minimum initial solar reflectance  AND aged reflectance is 0.15.  There are no steep slope performance requirements.

ASHRAE 90.1 and 90.2 standards include cool roof provisions as insulation credits. Standard 90.1 covers commercial roofing, and the criteria for cool roofing are min solar reflectance of 0.70 and min thermal emittance of 0.75.  In Standard 90.2 which covers residential roofing, the criteria are min solar reflectance of 0.65 and min thermal emittance of 0.75.  In both cases, the standard allows for a credit in insulation R-value if a cool roof, as defined by ASHRAE, is used. This applies primarily in the southern tier states of climate zones 1, 2 and 3.

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