Metal roofing provides a number of benefits over other roofing materials like asphalt, tile, or cement. Metal panel systems have not only outlasted other materials by decades, but they are now even more cost-effective and useful for residential and commercial applications. The range of hues that metal gives is one of its most appealing features, which is why having a selection of paint colors and finishes is crucial.
However, to what extent do you realize that the color of a metal roof would deteriorate over time? Perhaps you’ve heard the terms “fading” and “chalking” and are curious about the potential effects on your roof.
What Is Fading on Metal Roofing?
When materials such as water, pollutants, and chemicals in the air and particular surroundings react with the paint pigment, painted metal roofs begin to fade. Put another way, the color shift results from the pigment starting to degrade. While this change can completely alter or darken some colors, it often lightens them. It’s also important to note that different parts of the same structure may not always be exposed to the same elements, causing panels to fade unevenly.
In an outdoor setting, no amount of pigment or resin, regardless of the manufacturer’s choice, can keep the color forever. The easiest way to visualize what fading on metal will look like is to compare it to how an item of clothing can lose its color over time, as we covered in our discussion of metal roof paint warranties. The color fading that occurs with frequent washings and wearings doesn’t diminish the material’s durability or, in the case of a metal panel, its ability to shield your structure.
Nevertheless, there are ways to extend the life of the color on your roof, and the first step is to become knowledgeable about the components that cause fading, the different types of resins how well they withstand the weather, and the actual measurement of fading.
Factors That Cause Metal Roof Fading
UV or Sun Exposure
The amount and intensity of UV exposure that a metal roof or wall panel system receives is likely the primary determinant of how the panel will fade. For instance, a metal roof in Texas is more likely than one in Wisconsin to fade as a result of sun exposure. For this reason, paint systems are typically tested in places with extreme weather, such as Florida, to assess how well they hold up over an extended period of time.
Temperature
Extreme heat or cold will hasten color changes, but fading will occur at any temperature over time. Extensive studies and field testing further demonstrate that regular temperature changes degrade pigment by changing the chemical composition of the color.
Moisture
Over time, any type of moisture—rain, snow, ocean, condensation, etc.—can change the composition of any material. Resins are designed to withstand water and preserve pigment, but prolonged contact with water—especially standing water—accelerates the process. Acid rain or water that contacts the panels after exposure to harsh airborne contaminants can also affect fading. Please note that warranties sometimes do not cover metal roofing on structures located within a certain proximity to a bay, marsh, or shoreline. Before making a purchase, find out from the manufacturer whether moisture will have an impact on your metal roof or wall system.
Pigment
The paint applied on metal contains two distinct kinds of pigment:
- Organic: A naturally occurring pigment that is more prone to color fading and is composed of carbon-based petroleum chemicals. Organic pigments are what give most colors their vibrancy, richness, and brightness.
- Inorganic (ceramic): Mineral-based pigment made primarily of metal oxides. Paint that uses this type of pigment resists fading far longer than paint that uses organic pigments, as it is designed to meet strict performance standards. Earth tones, such as browns, greens, and beiges, make up these hues.
Resin
While pigment is what gives a paint system its color, resin is what keeps the color vibrant and gives it extra durability. The paint system is additionally bound to the metal substrate by resins.
“The durability of the color on a metal coil or panel is largely dependent on the resins used in paint systems. Consider these classes as the “good, better, best” ones to assist you in choosing the resin that will perform the best in your particular environment, even though their designations are quite technical.”
Top Coating System(s):
- Polyvinylidene fluoride (PVDF): About 70% of this resin is PVDF and the remaining 30% is acrylic. PVDF resins, also known as Kynar 500® or Hylar 5000®, are the greatest protective coatings on the market because they can withstand severe temperatures, sunlight, oxygen, humidity, and even airborne pollutants. Due to their exceptional longevity, coils built with this resin tend to have the longest chalk and fade warranties, usually lasting up to 40 years. However, the cost of these coils is significantly higher.
- Fluoroethylene Vinyl Ether (FEVE): Excellent protection coatings, FEVE coatings can outperform PVDF coatings under a variety of conditions, including high temperatures, direct sunlight, humidity, oxygen, and even airborne pollutants. These coatings also offer similar chalk and fade warranties to PVDF. To meet customer needs, manufacturers can provide these coatings in a variety of color schemes and gloss levels.
Better Paint System(s):
Silicone-modified polyester (SMP): PVDF is superior to SMP coatings in terms of quality and warranty choices. Silicone-modified polyester (SMP) coatings, composed of a blend of silicone and polyester materials, offer excellent protection against severe weather and provide paint warranties for up to 35 years. These coatings are renowned for their durability and long-term performance.
Good Paint System(s):
Plastisol: A metal coil intended for use in a highly corrosive or demanding environment is typically coated with Plastisol resin, which is composed of plasticized vinyl. Plastisol shields against weather-related deterioration, but be aware that this resin can alter the pigment of vivid, bright colors.
Polyester: Polyester is a synthetic polymer that is less expensive than other resins but isn’t the best at preventing fading on metal roofs or wall panels. Warranties still protect polyester-coated coils, though they typically last only ten years for chalk and fading
How to Measure Fading
According to ASTM International standard D-2244, the Hunter Lab uses the Delta E (∆E) instrument to establish the standard for measuring fading on a metal panel. The difference between a paint sample and the paint’s original hue is the number that stands for “E” in ∆E. When a sample is measured at ∆3, for instance, it indicates that the color has altered by three Hunter Delta E units from the first reading. To see an example of paint fading, view the sample photo on the right.
Within a specified time frame, paint system warranties cover fading up to a specific Hunter Delta E (∆E) unit. For instance, if your metal roof has a 30-year warranty against color fading up to five (∆5) Hunter units and you believe the paint has faded more than five units before the warranty has run out, get in touch with the manufacturer. They will visit the location and examine the panels to determine if an incident other than a paint system malfunction changed the color. The manufacturer can then look into the matter more and decide on the best course of action.
The warranty should specify the ∆E units and indicate whether any particular colors are subject to different terms. Metallic colors typically have no color warranty because a color spectrophotometer cannot measure them, while brighter colors usually come with a lower fade warranty.
Since metal roof panels and metal wall panels receive different amounts of sunlight, most warranties specify different ∆E units for them, with wall panels typically covered at a lower ∆E value than roofing.
Chalking on Metal Roofing: What Is It?
Chalking refers to the white residue that may eventually appear on a painted or coated metal surface. A panel’s resin starts to deteriorate and break down when it is exposed to sunshine and UV radiation. As the resin breaks down and becomes exposed to more light, oxygen, and other contaminants, it loses its adherence to the surface, causing the degraded particles to start turning white. Eventually, the surface of the metal will show these particles to the unaided eye.
The change is frequently not noticeable. You can see the chalky residue on your skin, though, if you swipe the panel with your finger.
The paint system, particularly the type and grade of resin, affects the degree of metal roof chalking. Based on the type of resin, chalking typically occurs at the following rates, assuming the same environmental conditions:
- Plastisols (First to chalk)
- Polyester
- SMP
- PVDF or FEVE (Last to chalk)
Measuring Chalking on Metal Panels
Technicians use one or more techniques from the ASTM D-4214 standard to measure chalking. This standard also specifies the numbering system’s specifications. Numbers 1 through 10 are assigned, with Number 1 representing the worst condition and exhibiting severe chalking (see the top photo). Many times, warranties cover over-scribing up to a certain amount using a specified technique.
For instance, the testing procedure would adhere to the following guidelines if a manufacturer claims that their guarantee covers chalking in excess of Number 8 utilizing Method A, commonly known as the Cloth Tape Method:
7.1 Cloth Tape Method (Test Method A)
7.1.1 Material: Fabric to rub against the surface under test, as decided upon by the manufacturer, user, or other interested parties. Particularly successful are black (or white for dark coatings) wool felt, velvet, and velveteen.
7.1.2 Method: After encircling the fabric around the tip of the index finger, apply medium pressure in a 2 to 3-inch (50 to 75 mm) stroke to the coating while it is being observed. Take the cloth off and match the chalk mark with Photographic Reference Standard No.
NOTE: To measure medium pressure, place your finger on a scale or balance and press down until you reach three to five pounds of pressure.
Testing the Coating Systems on Metal Walls and Roofs
Keep in mind that paint suppliers and manufacturers actively test their paint systems under the most demanding circumstances long before releasing their products onto the market. In order to provide you and other customers with the appropriate warranty depending on the location of your structure, testing enables manufacturers to assess how effectively their goods function. A few of the assessments look for:
- Chalking
- Fading
- Corrosion
- Flaking
- Cracking
- Peeling
As an illustration, a few typical paint testing techniques are as follows:
Natural exposure: In tropical climates, painted sample panels are oriented southward on elongated outdoor test racks to receive the maximum amount of solar radiation. To ascertain the degradation cycle of the paint system, we keep the paint samples on the racks for a predetermined amount of time.
Indoor accelerated testing: To find out how well and how long certain paint systems can withstand the elements, product samples are placed in machines that replicate real weathering conditions, such as rain, wind, sunlight, heat, and humidity. Although the most accurate indicator of a product’s performance is natural exposure, accelerated testing makes it possible to analyze more materials in less time.
It is important to inquire with your manufacturer about the testing procedures their paint supplier employs prior to the release of their metal panel systems, as well as the verification of these tests. If the manufacturer is willing to talk to you about the outcomes of weather testing and whether the items meet industry standards, you’ll have a better idea of how reliable they and their products are.
Conclusion
Metal roofing, celebrated for its longevity and resilience, naturally wears over time like any other material. Understanding the nuances of metal roof color chalking and fading is crucial before investment. These phenomena, influenced by factors like UV exposure, temperature fluctuations, and moisture, gradually alter the roof’s appearance and integrity. By choosing high-quality paint systems and conducting regular maintenance, you can significantly extend the life of your metal roof’s color. Staying informed about the specifics of your warranty can safeguard your investment, enhancing the appeal of metal as an ideal option for your roofing needs.
FAQs: Metal Roof Color Chalking and Fading
1. What Causes Metal Roof Color Fading?
UV rays, harsh weather conditions, and airborne chemicals primarily cause color fading on metal roofs by degrading the paint pigment over time.
2. What is Chalking in Metal Roofing?
Chalking refers to the appearance of a fine, white, powdery residue on the paint surface of metal roofs. This occurs when the resin in the paint system breaks down due to UV exposure and environmental pollutants.
3. How Can I Prevent Chalking and Fading on My Metal Roof?
To minimize chalking and fading, opt for high-quality paint systems with enhanced UV resistance and durability. Regular maintenance, including periodic cleaning, also helps maintain the color and finish of the roof.
4. Are There Warranties That Cover the Chalking and Fading of Metal Roofs?
Yes, many metal roofing manufacturers offer warranties that cover chalking and fading for a specific duration. The extent and terms of coverage vary based on the paint system used and the expected environmental conditions at the installation site.
5. Does the Color of the Metal Roof Affect the Rate of Fading and Chalking?
Darker colors generally fade more visibly than lighter ones due to greater absorption of heat and UV light. However, inorganic pigments used in lighter colors often have better resistance to chalking and fading than the organic pigments found in more vibrant colors.
