NEOtech Coatings > Solar Reflectance Index (SRI) in Detail

Solar Reflectance Index (SRI) in Detail

The tests designed by laboratories for SRI (Solar Reflectance Index) are only designed to test very specific points of heat and light and not how all points work together. The laboratory tests “assume” theories that are not accurate as with emissivity. The laboratory testing also states that standard white paint reflects 70% of the heat or light. This isn’t correct. Touch a white car bonnet on a warm day and it will burn your hand. It does not reflect 70% of the heat, only light, not heat.

Many assumptions come with established tests that are not correct, but accepted by industry because they needed something to use, like Tio2 that blocks Infrared. It may block 10%, but because it blocks 10%, they claim it blocks Infrared and you are supposed to believe it blocks all the Infrared.

What is defined as Solar Reflectance?

Solar reflectance, often referred to as albedo, is the measure of a material’s ability to reflect solar energy (sunlight) including visible, infrared, and ultraviolet light. It is expressed as a fraction or a percentage, indicating how much of the incoming solar energy is reflected by the surface. High solar reflectance implies better reflection of solar rays, contributing to lower surface temperatures and reduced heat absorption. This concept is crucial in fields like sustainable building and thermal insulation coatings.

Solar reflectance is the total of radiation waves measured but IR is limited in this measure of waves as seen below in Red. If this were true, then the white car hood would be cool. This comment was verified by the Solar reflectance lab telling me that only parts of the IR is seen by the spectroradiometers.

If albedo is the measure of whiteness how can it measure infrared?

Albedo is commonly associated with the whiteness or reflectivity of a surface in the visible spectrum, but it actually encompasses the reflectivity across the entire spectrum of solar radiation, including infrared. While we often think of albedo in terms of visible light (like the whiteness of snow), materials can have different reflective properties in the infrared range. This means a surface might not appear white in the visible spectrum but can still have a high albedo for infrared radiation, reflecting a significant portion of the sun’s infrared rays. This is especially relevant in thermal insulation materials, where high infrared reflectivity is desirable for energy efficiency. We know that snow does not block IR, it is the thickness of snow that maintains cool on the ground.

Where exactly is the proof it measured infrared?

The measurement of albedo in the infrared spectrum is established through scientific research and empirical data. Specialized instruments like spectroradiometers are used to measure the reflectance of different surfaces across various wavelengths, including the infrared range. These measurements provide a comprehensive profile of a material’s reflective properties.

In the context of thermal insulation and building materials, research studies and product testing often include infrared reflectance data to demonstrate the material’s effectiveness in reflecting infrared solar radiation, which is a significant component of heat transfer. This data is crucial for products like thermal insulation coatings, where high infrared reflectance can significantly impact energy efficiency and heat management. “Often include IR reflectance data”. – key to how these machines work. They do not catch all the IR waves and any professor that tries to say it does can be proven wrong.

The proof of infrared measurement in albedo can typically be found in detailed product specifications, scientific papers, and reports from materials testing laboratories.

A spectroradiometer can see a large portion of the IR spectrum, but not necessarily every single wavelength. The exact range of IR wavelengths it can detect depends on several factors:

Calibration: The spectroradiometer needs to be calibrated to accurately measure the intensity of each wavelength. Calibration can be limited by the available reference sources and the accuracy of the calibration process.

Atmospheric absorption: The Earth’s atmosphere absorbs certain wavelengths of IR radiation, creating gaps in the spectrum that a ground-based spectroradiometer cannot measure.

Do heat reflective paints reflect infrared?

Yes, heat reflective paints, also known as thermal insulation coatings, are designed to reflect infrared radiation. These paints contain specialized pigments that are effective at reflecting the infrared portion of solar radiation. By doing so, they reduce heat absorption in the surfaces they are applied to, helping to keep buildings, structures, or other coated objects cooler under sunlight. This is a key feature for energy efficiency, particularly in warm climates, as it can significantly reduce cooling costs and energy usage. The effectiveness of these paints in reflecting infrared radiation is a major factor in their insulation properties. Only coatings with particular compounds designed specifically to match the IR wave size can block out the waves.

From asking Bart (Goggle’s AI), Titanium Dioxide (Tio2) and Zinc Oxide (ZnO) are the two that it knows can block IR. Everyone uses Tio2 to make the paint ‘hide” the darker surface it is painted over. Ability to block IR is very limited or every house paint would be blocking IR and all houses would be cool. Zinc Oxide is also the wrong compound. It has “some” ability but very limited. It is used to mainly reduce mold/mildew growth. This is where professors don’t have a clue about chemical compounds and how they actually work inside a coating film. They take the information given by the supplier in a dry powder form and states it is the same as when blended into a coating – mixed with other ingredients and reduced in intensity. They have never studied it after made into a coating to see the true effectiveness.

What’s the difference between heat reflective paints and thermal insulation coatings?

Heat reflective paints and thermal insulation coatings are terms that are often used interchangeably, but they can have some distinctions:

Heat Reflective Paints: These are typically paints designed primarily to reflect solar radiation, including the visible and infrared spectrum. Their main function is to keep surfaces cooler by reflecting sunlight. They are commonly used on exteriors like roofs and walls to reduce the heat absorption of a building. Again, they believe that the more Tio2 or Zinc Oxide, this will block IR and do the same blocking ability as when in a compound state in 100% strength dry. Stupid thinking but they don’t know “after’ it is blended and reduced in intensity.
Thermal Insulation Coatings: While these coatings also reflect heat, they often have additional properties that improve thermal insulation. They might include components that provide better thermal resistance, reducing heat transfer not just from solar radiation but also from other heat sources. These coatings can be more advanced and might be used in a wider range of applications, including industrial settings. They have no clue here as to what compounds make an “insulation coating”. They are only using general chemical relationships which don’t mean a thing after batching a paint.

In practice, the terms are sometimes used to describe the same products, especially when those products serve both functions of reflecting heat and providing thermal insulation. However, the specific formulation and intended use can vary, so it’s important to look at the product specifications for the exact properties and applications.

What would be the core specifications to differentiate?

To differentiate between heat reflective paints and thermal insulation coatings, you can look at the following core specifications:

Solar Reflectance: This measures how much of the sun’s energy is reflected by the coating. Higher solar reflectance indicates better performance in reflecting visible and infrared light. They talk about waves, but “light” is their biggest measurement in the thought light carries most of the heat which it does not.
Thermal Emittance: This indicates how effectively a material releases absorbed heat. A higher emittance value means the surface will cool down more quickly once the heat source is removed. Key- “after heat source is removed”. Concrete will cool very quickly after the sun goes down due to porosity releasing the heat and increased surface area of the pores. During the heat of the day, it will burn your hand off like the hood of a car. We are talking about during the heating of the radiation, not when it is removed. Can the Tio2 and Zinc Oxide throw off the heat during the day in direct sunlight – no – the white car hood clearly shows this.
R-value: This is a measure of thermal resistance. Higher R-values indicate better insulation properties, showing more effective resistance to heat flow. As the ASTM test states, when the insulation material reaches “heat flux” or full, they shut the test down. This simply means that after it hits heat flux, it no longer resist heat transfer and has no to very little R-value. They never talk about this – “when it reaches heat flux, the test is terminated”. This was pushed by fiberglass in 1980 when the engineers reviewing the testing published that the fiberglass chose only select samples to test and only tested 1.5” to 3” thickness to get their R-value. The engineering review stated clearly that the R value does not relate to any thickness beyond 3”, but Fiberglass uses it as a linear measurement meaning they take the 3” R-value result and extend that out to 10” and beyond when the FTC itself stated this is false and deceptive. All this begins to let you know that the published ideas or facts are not facts but only suggestions about all of the information published on the AI internet.
Thickness of Application: Thermal insulation coatings might require a thicker application than heat reflective paints to achieve the desired insulation effect. Again, this relates specifically to the ceramic compounds used. If they are thick film, closed cell ceramics that hold heat on the surface, then thickness becomes less of a requirement.
Infrared Reflectance: Specifically measures how much infrared radiation is reflected, which is key for reducing heat absorption from the sun.
Durability and Longevity: How long the coating maintains its reflective and insulating properties under various environmental conditions.
Permeability and Breathability: Some thermal insulation coatings might also have specifications for moisture and vapor permeability.
Chemical Composition: The specific ingredients or technologies used, such as microspheres or particular reflective pigments, can differentiate the two.

By comparing these specifications, you can determine whether a product is more suited as a heat reflective paint or a thermal insulation coating.

How can a coating have an R value if they aren’t thick?

Coatings with thin applications can indeed have an R-value, though it’s typically much lower than traditional insulation materials like foam or fiberglass. The R-value of a coating is influenced by its inherent insulating properties, which are a result of its chemical composition and the technology used.

Advanced Materials: Some coatings include materials like ceramic microspheres or other insulating particles. These materials can enhance the thermal resistance of the coating, even in thin layers.
Reflective Properties: While R-value is primarily about resistance to heat flow, coatings that highly reflect infrared radiation can reduce heat gain, indirectly contributing to overall thermal performance. This isn’t a direct increase in R-value but can have a similar effect in certain applications. This is blocking heat initial heat load versus heat load and transfer “until” it reaches heat flux.
Cumulative Effect: In real-world applications, even a small R-value can be significant. When applied to surfaces that already have some insulating properties, these coatings can contribute to an overall increase in thermal resistance.

It’s important to note that while these coatings can contribute to thermal insulation, their R-values are generally much lower than traditional insulation materials. They are often used as part of a broader insulation strategy rather than as a standalone solution for high thermal resistance.

Do coatings with ceramics improve the R-value?

Yes, coatings that incorporate ceramics, particularly in the form of microscopic spheres or particles, can improve the R-value, albeit typically to a modest extent. These ceramic components enhance the insulation properties of the coating through several mechanisms: Problem with hollow spheres is that they can absorb and hold heat inside the sphere itself which will minimize its function. Also, much advertising is that they can reflect heat waves – no more than your glass window – so not that much.

Reflective Properties: Ceramic particles can reflect radiant heat, particularly infrared radiation, which helps in reducing heat absorption from the sun. This is a general statement. Unless the compound matches the size of the IR wavelength, it cannot have much effect. Studied by the German engineers in 1932.
Low Thermal Conductivity: Ceramics generally have low thermal conductivity. When incorporated into coatings, they reduce the rate of heat transfer through the coating.
Air Entrapment: The microspheres or particles in the coating can trap air, which is an excellent insulator. This trapped air can reduce heat conduction. Trapped air will migrate out and loose its effectiveness. This happens in foam over time.

However, it’s important to manage expectations regarding the level of insulation improvement. While ceramic-infused coatings do enhance thermal resistance and can contribute to energy efficiency, they typically do not replace traditional insulation materials in terms of overall R-value. Their primary use is often for situations where traditional insulation is impractical or as a supplemental measure to existing insulation strategies.

How can you test the R-value of a coating?

Testing the R-value of a coating involves measuring its resistance to heat flow. This is usually done in a controlled laboratory setting using standardized methods. Here’s a general overview of the process:

Sample Preparation: A sample of the coating is applied to a substrate material according to the manufacturer’s specifications. It’s important that the coating is applied and cured as it would be in a real-world application.
Guarded Hot Plate Test: One of the most common methods for measuring R-value is the guarded hot plate test. This test uses a flat plate, heated to a steady temperature, and the coating sample is placed against this plate. The opposite side of the sample is kept at a constant cooler temperature. If you take a plate, coat over it and then press the cold plate against it, the coating has no ability to throw off heat as coatings are designed to do. Fiberglass and standard insulation materials cannot reflect heat or use emissivity. These ASTM tests established for this materials cannot be used in any way on coating. This is a totally wrong approach, but AI has no idea of the real abilities of insulation coatings compared to how testing is set up. The only ASTM test established for using insulation coating is ASTM C1363 HOT BOX.
Heat Flux Measurement: Sensors measure the amount of heat passing through the sample from the hot side to the cool side. This heat flux, along with the known temperatures on either side of the sample and its thickness, is used to calculate the thermal resistance or R-value. Remember, when the material reaches heat flux (full of heat), the test is turned off. This could be noon, so this is ridiculous as to showing effective insulation. If it cannot work all day and into the night, it offers nothing. Again, FIBERGLASS set this test up so they did not want this question raised about it becoming full of heat and then what???
Steady-State Conditions: The test is conducted until steady-state conditions are achieved, meaning the heat flow and temperatures remain constant over time. As Georgia Tech Univ (Engineering College) tested and proved, Steady State cannot be tested and used in real-world because not a single measurement can change during the testing, so the only place this insulation test can be done is inside a ‘controlled lab” with no changes in wind, humidity, clouds, etc. Again, who set this up – Fiberglass.
Compliance with Standards: It’s important that the testing complies with relevant standards, like ASTM (American Society for Testing and Materials) or ISO (International Organization for Standardization) standards, to ensure accuracy and comparability of results. They only have one that incorporates all three : radiation, conduction and air movement- ASTM C1363.

Professional testing laboratories conduct these tests, providing an unbiased evaluation of the coating’s thermal performance. The results offer valuable data for comparing different coatings and understanding their effectiveness as insulation materials.

Is there a video online that demonstrates Solar Reflectance including infrared?

Based on a quick search, here’s what I found.

I found information on a study from “Nature.com” that discusses photonic structures used for radiative cooling. These structures demonstrate high solar irradiance reflectance and thermal emissivity in the mid-infrared (mid-IR) range. For example, one structure showed a solar irradiance reflectance of 97% in the solar range and a thermal emissivity of 95% in the mid-IR range. These properties are key for passive radiative cooling, indicating that the coatings are effective in reflecting solar radiation, including infrared wavelengths. As usual, testing cannot incorporate all the wave lengths and forms of heat blocking in one test and at a 100% as stated by AI.

Is it possible SRI is combining emissivity IR with Solar Reflectance?

Yes, it is possible that the Solar Reflectance Index (SRI) combines aspects of both solar reflectance and emissivity in the infrared (IR) spectrum. The SRI is a measure that incorporates both the reflectivity of a surface in the solar spectrum and its ability to emit absorbed heat. Essentially, it’s a combined metric that accounts for how a material reflects solar energy and how effectively it releases absorbed heat, particularly in the infrared range. This makes SRI a comprehensive indicator of a material’s overall thermal performance in terms of reflecting and emitting solar energy. Combines “aspects” and only does samples of each wave. Light reflecting is confused with heat in many of these tests.

Just because it can measure IR emissivity is this assuming IR is being measured before it hits the surface?

In the context of Solar Reflectance Index (SRI) and infrared (IR) emissivity, SRI typically measures how a material reacts to solar radiation that it has already received. It evaluates both the solar reflectance (how much solar energy is reflected) and the thermal emittance (how effectively the material emits absorbed heat). The IR emissivity component of SRI does not assume measurement of IR before it hits the surface. Instead, it focuses on the material’s behavior after absorbing solar energy, including IR radiation. There is still a confusion in the testing between “light” and actual heat in the waves.

As the waves hit a surface, it starts the molecules of the surface material to react and vibrate at a faster rate to open the surface to a faster loading of heat from the waves and transfer of this heat through the surface to the cool side. This is no absolute in how much heat is reflected off the surface before it is loaded or absorbed and transferred to the cool side.

So how can it measure actual infrared heat before it’s absorbed when it’s being influenced by what IR is being emitted? They are 2 different results.

You’re correct in noting that solar reflectance and infrared emissivity are distinct properties. Solar reflectance measures how much solar radiation, including IR, is reflected by a surface before it’s absorbed. In contrast, emissivity deals with how efficiently a surface emits absorbed heat, particularly in the IR spectrum.

To accurately measure these properties separately, specialized instruments and methodologies are used. For solar reflectance, spectroradiometers can measure the reflectance across the solar spectrum (including IR) as it interacts with the surface. For emissivity, measurements typically focus on how the material emits heat after it has absorbed energy.

Therefore, while SRI combines these aspects to assess overall thermal performance, it doesn’t conflate the distinct processes of reflecting incoming IR and emitting absorbed IR. Each component is evaluated independently before being integrated into the SRI value. They should have a test designed that does “combine or conflate” the aspects to get a more realistic understanding when both forces are working together. One force might cancel the other force?

Where is an example each component is evaluated independently before being integrated into the SRI value?

The Solar Reflectance Index (SRI) is calculated by independently measuring solar reflectance and thermal emissivity of a material, and then combining these values. Solar reflectance is measured using a UV-VIS-NIR spectrophotometer, which assesses how much solar radiation is reflected by the surface. Thermal emissivity, indicating how much energy a material radiates compared to a black body at the same temperature, is measured using an emissometer. The SRI is derived from these two values according to standards like ASTM E1980-11 and ASTM E903-12, which ensure accurate and consistent evaluation of materials’ thermal and reflective properties.

Again, emissivity is not a complete record of heat being thrown off. After the heat hits a surface, it is absorbed. The emissivity is a measure based against a black box. A black box absorbs 100% and emits off 100% is a equalization. Therefore, what if the emissivity is simply if a coating surface absorbs 95% and shows an emissivity of 95%, would that mean that it absorbed and transmitted 95% and simply equalized itself with a throw off of 95% – just like the black box that it is judged against???? Yes it is. So is this test accurately stating all the 95% of heat was thrown off before it was absorbed and transferred like the black box- no, it is only stating is equalized with the amount it absorbed with the amount if throws off.

Can you find somewhere online that shows the formulation of SRI in a real world sample?

A real-world example of calculating the Solar Reflectance Index (SRI) can be found through the Building America Solution Center’s SRI Calculator. This tool, developed by the Lawrence Berkeley National Laboratory, computes the SRI and roof surface temperature based on solar reflectance and thermal emittance using the ASTM standard E 1980. It requires input of the solar reflectance and thermal emittance values of a material to calculate the SRI, demonstrating how these components are evaluated independently before being integrated into the SRI value. For more detailed information and to use the calculator, you can visit the Building America Solution Center’s SRI Calculator.

What compounds are added to paints to block IR waves?

Several compounds can be added to paints to block IR waves, each with its own advantages and disadvantages. Here are some of the most common:

Metal oxides:

Titanium dioxide (TiO2): This is the most widely used pigment for infrared blocking paints. It has a high refractive index, which means it reflects a large portion of the incident IR radiation. It is also relatively inexpensive and non-toxic.

Zinc oxide (ZnO): This is another common pigment for IR blocking paints. It also has a high refractive index and is non-toxic, but it is less effective at blocking IR than TiO2.

Iron oxides: These pigments are available in various colors, including yellow, red, and black. They can be used to block IR radiation while also providing color to the paint. However, they are not as effective at blocking IR as TiO2 or ZnO.

Ceramic particles:

Hollow ceramic spheres: These spheres are filled with air, which helps to reflect IR radiation. They are lightweight and can be easily incorporated into paints.

Alumina (Al2O3): This ceramic material has a high refractive index and is very effective at blocking IR radiation. However, it is also expensive and can be difficult to disperse in paint.