What is the best color of roof for energy savings?
If you are looking to save on your energy bills, your roof might be the place to start. Especially the color of your roofing material can affect how much heat your home absorbs from the sun which impacts your cooling costs.
I want this guide to be the one-stop resource for homeowners looking to understand how roof color can affect their energy bills. Therefore, I have included everything you need to know about how to choose the best color of roofing for your home.
How does the color of the roof affect energy efficiecy?
The color of your roof can have a large impact on how much heat and cooling your home absorbs. The darker the material, the more heat it absorbs. If you have dark roofing material on your home, you will spend more on cooling costs than homes with lighter roofs.
Here is why it happens so. When light hits any surface it is either reflected or absorbed by that surface.
Some colors reflect certain wavelengths of light energy which is what those colors are seen as. For example, a green leaf appears green because it absorbs all other wavelengths except for green. The green is reflected off the leaf and into our eyes.
Standard white color reflects all light that hits it and absorbs no light. While the standard black color absorbs all colors and reflects none. By knowing this, you can guess that the darker the color of your roof is, the more heat it absorbs.
Standard white color is more reflective than all other colors. This is why there is an industry term “white roof” (a type of cool roof) that is used to describe roofs with high albedo (reflectivity).
Most roofs are not designed as all-white roofs or all-black roofs. They are usually a color somewhere in between, absorbing a certain percentage of light and reflecting the rest.
Then how you could know your intended roof color absorbs the least amount of light?
A lot of times colors seem to be very similar in tone. If you were to look at a manufacturer’s color palette, you would see that most of the colors are very close to one another.
Knowing this complication, the industry has come up with a very good way of comparing different colors in terms of how much light they reflect.
It is called the Solar Reflectance Index, or SRI for short. This index tells us how much heat a certain color reflects in comparison to a standard white color.
The SRIs are numbers ranging from 0 to 100+, which tell us how much light energy a surface reflects in percentage.
For example, a standard white color has an SRI of 100. Because it absorbs no light and reflects all possible wavelengths. On the other hand, the black color has an SRI of 0. Because it absorbs all light and reflects no wavelengths.
So, the higher the SRI of a roofing color, the less heat it absorbs, and the lower the SRI, the more heat it absorbs. A lot of roof material manufacturers should be able to provide you with the SRI data for your desired roof product.
However, it is important to note that some manufacturers’ SRI data may only be self-claimed and not truly tested by an independent laboratory. Ideally, SRI values of roof materials should be provided by a third-party testing company that uses ASTM E 1980 testing procedures.
Now you know the basics of how roof colors impact energy efficiency. However, we are still missing some important details that you will need to know about.
Is SRI data of your roof material an evergreen metric?
No, the SRI values of roof materials are not evergreen for the entire life of that roof product. Instead of being an evergreen metric, the SRI of a roof product changes as that material ages. As your roof material ages, it slowly loses its reflective properties and absorbs more heat from the sun.
The amount of loss in reflectivity varies depending on environmental conditions and the type of roofing material.
Therefore, the industry came up with another metric called 3-year SRI. The 3-year SRI tells you how much heat a material reflects after three years of exposure to the environmental elements.
This is a much better metric to use than just standard SRI. Because by the time three years have passed, you can almost estimate how much your roof will be losing its reflectivity.
A roofing material with a higher standard SRI reflects more heat than one with lower standard SRI values. However, by assigning all the materials an initial 3-year SRI value, you can easily compare their effectiveness after 3 years of exposure to the elements.
This is important since the roofing material you choose today may not be the same material that is on your roof five years from now.
How does surface glossiness affect the SRI of your roof?
The surface glossiness mainly contributes to how much light is reflected off the roof. The more matte (or dull) a surface is, the less light it will reflect.
While the more glossy (or shiny) a surface is, the more light it will reflect. This is why the glossiness of your material will have an impact on your roof’s SRI.
Fortunately, there are tested SRI values for the most commonly used colors and gloss levels you will see in the marketplace.
How do roof surface finish and material affect SRI?
The roof surface’s finish and material are very important when it comes to SRI values.
Typically, the smoother the surface is, the more light it will reflect. This is because there are no microscopic grooves, pores, or other surface impurities that can reduce the amount of light being reflected.
It is important to note that a perfectly smooth surface will have a higher SRI than a porous surface even if they are both the same color and gloss level. Therefore, the color of your roof is only as good as the surface finish of your material.
How does paint or coating affect the SRI of your roof?
The surface coating and paint on your roof are extremely important when it comes to your roof’s SRI. Therefore, choosing the right roofing paint or coating is key to reducing energy costs.
If you have a high SRI roofing material but not well-planned and executed coating and paint application, your roof’s SRI will take a turn for the worse. On the other hand, if you have a low SRI roofing material and you choose a coating or paint with high reflectivity, your roof’s SRI will soar.
Therefore, it is best to use the paint or coating product your roofing material manufacturer recommends or your roofing installer suggests.
Certain companies already have their own line of paints and coatings that are optimized for their products. This means you will not need to worry about choosing the appropriate paint or coating product.
There are also many engineered coatings and paints on the market that are designed to improve the reflective properties of your roof. They are typically nano- or micro-metallic based and will not change the color of your roof.
Does dirt on the roof decrease SRI?
Yes, dirt and other surface contaminants will decrease your roof’s SRI. This is because the dirt and other contaminants block sunlight from being reflected off the surface.
Therefore, it is important to keep your roof clean by regularly cleaning dirt and other contaminants that may accumulate on your roof.
Use Energy Star roof products
Energy Star roof products are designed to reduce energy costs for the building where they are installed.
For example, Energy Star shingles are designed to reflect more heat than most other standard shingles. This means that the shingles can keep your building cooler and reduce the need for air conditioning, which will save you money on utility bills.
There are already thousands of Energy Star qualified roof products on the market. Therefore, you should look for your roofing materials to carry the Energy Star label for maximum energy savings.
The color of your roof is important for your home’s energy efficiency. To ensure the best thermal performance, consider using materials with high SRI values. The selected roof material’s SRI value should be greatly retained over the years of exposure to the elements.
Glossy colors are known to be more reflective than matte colors. Therefore, if possible choose the glossy version of your desired roof color to increase its SRI value.
Roofing paints, coatings, and finishes are just as important for improving the SRI of your roof as the chosen material and color. Therefore, make sure you choose a product either recommended by the roofing material manufacturer or suggested by the installer.
Finally, make sure to clean your roof regularly to prevent dirt buildup on the roof. This will ensure the best possible performance of your roof’s SRI.