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Can Solar Reflective Roof Shingles Unlock Energy Savings for Your Home?
Solar reflective shingles, also known as cool roofs, are an increasingly popular topic due in part to growing concern about climate change and rising HVAC costs. As a homeowner with rising expenses of your own, you’re likely interested in reducing these utility costs. So, how about installing solar reflective shingles of your own? Do they make sense for your home? Will they pay off in the long run? While solar reflective shingles can be an energy efficient choice for some, their benefits vary depending on your climate.
In the right weather conditions, solar reflective shingles can help keep your roof cooler, which can help lower energy bills and potentially decrease CO2 emissions from air conditioning. In fact, some local and state governments have enacted building codes that require roofing materials to pass tests to show they help improve energy efficiency in their areas. One of the ways to meet these building codes is by having a roof that meets their standards for Solar Reflectance Index (SRI). While these codes are a requirement in some areas, in others they are incentivized through rebates and tax credits.
The Science Behind SOLAR REFLECTIVE Roofing
Due to its location and function, your roof is a great place to view thermodynamic principles in action. For example, let’s discuss what happens there on a typical sunny day.
- Solar energy from the sun hits the surface of your roof.
- Some of this energy is absorbed into your roof.
- It is then transferred into your home through conduction.
One of the ways you can disrupt this heat transfer is through reflectance. Similar to how a mirror reflects an image to your eyes, reflective shingles cause more solar energy to bounce back into the atmosphere than non-reflective shingles. This reduces the amount of radiant energy absorbed into the roofing material and, in turn, your home.
Photo credit: https://coolroofs.org/resources/home-and-building-owners
A wide range of materials use reflectance. These roofing materials can vary from commercial-grade paints or coatings to reflective low slope membranes, to metal, clay or asphalt shingles on a residential building. Homes using asphalt shingles in the state of California frequently use solar-reflective granules to qualify as cool shingles.
So, what defines a solar reflective shingle or “cool roof”? Since building codes vary by region or structure, the phrase cool roof can have different meanings. However, a common benchmark used among these standards is SRI (Solar Reflectance Index). The SRI of a material is calculated based on two properties: solar reflectance and thermal emittance. Though we've discussed solar reflectance, a material’s ability to reflect sunlight into the atmosphere and away from your home, the other half of this equation is thermal emittance (TE). Thermal emittance depends on the material’s ability to radiate the heat it has absorbed back into the atmosphere. A higher thermal emittance means more heat will be radiated back into the atmosphere, and less will be conducted into your home.
California Title 24 and Green Building Standards Code of Los Angeles County and Los Angeles City Cool Roofs Ordinance
California has been at the forefront of the push toward solar reflective roofing shingles. While the state’s perpetually sunny weather is a contributing factor, its abundance of densely populated metropolitan areas also plays an important role. Due to highly concentrated infrastructure and limited greenery, these areas can experience Urban Heat Island Effect causing them to be significantly warmer than surrounding rural locales. Title 24 aims to ensure buildings in California meet standards for safety, energy conservation, and design.
Owens Corning® Reflective Shingles Options
- In California: The COOL Roof Collection by Owens Corning is an innovative solution for certain climate regions. TruDefinition® Duration® COOL Shingles meet standards set by California's Title 24, Part 6, while TruDefinition® Duration® COOL Plus Shingles meet the more stringent requirements within LA County- the Green Building Standards Code of Los Angeles County and Los Angeles City Cool Roofs Ordinance.
- Outside of California: Owens Corning® Roofing asphalt shingles with light hues naturally reflect the sun better and have greater solar reflectance than darker colors. The Solar Reflective Index (SRI) Options with Owens Corning® TruDefinition® Duration® Asphalt Shingles technical bulletin reviews color options that will help you achieve solar reflectivity.
When SOLAR REFLECTIVE Shingles Aren’t So Helpful
So, if cool shingles are beneficial, why don’t all states require them? And will solar reflective shingles save you money on energy costs even if you don’t live in California? Well, like many things in real estate, the answer is location, location, location.
Consider your region’s climate. While Minneapolis, MN and Houston, TX both can experience similar high temperatures during summer months, the winter season looks very different. The high temperatures in Houston during the winter months dip down to the low end of 60 degrees Fahrenheit, while the Minneapolis region drops into the upper 20’s for their highest temps. As we know, cool roofing shingles work by reflecting solar energy. During these cold months, homeowners in Minneapolis or similar climates would want their shingles to absorb more energy rather than reflect it to help keep their homes warm. More simply said, reflective shingles make the most sense in areas where you use air-conditioning or cooling more days a year than you use heating.
A 2024 study conducted by the Oak Ridge National Laboratory shows the cost impacts on energy savings for residential buildings with reflective exteriors. The study compares three vastly different climates: Houston, TX, Baltimore, MD, and Minneapolis, MN. The outcome showed that in the Houston climate, energy savings are achieved and increase with greater reflectance. However, those savings were drastically lessened in the Baltimore region, and the Minneapolis region saw energy costs rise as solar reflectance increased. (Ref: Table 18.)
Some good sources of information on historical climate in your area are the National Weather Service as well as the US Energy Information Administration. The National Weather Service can provide historical data on temperature throughout the year, and the Energy Information Administration provides a helpful graphic summarizing heating versus cooling degree days based on region.
Alternative Strategies for an Energy-Efficient Roof
In addition to solar reflective shingles, there are many other products that can help your home optimize energy usage. The U.S. Environmental Protection Agency (EPA) ENERGY STAR program has a number of different recommendations to help your home and/or roof assembly become energy efficient.
- Attic Air Sealing, helps your home reduce air escaping from the attic into the conditioned living spaces of your home.
- Attic Insulation, in the proper amounts resists heat flow, helping your home stay cooler in the summer and warmer in the winter.
- Proper attic ventilation reduces humidity and allows hot air trapped inside during summer months to flow out.
- Roofing solar panels capture solar radiation and transform it into a useful energy source. Talk with your contractor about the benefits of installing solar panels with your roof.
PhotoCredit: EPA/Energy Star
Are Solar Reflective Shingles Right for Me?
If you live in Climate Zone 1, 2 or 3 and have more cooling days (days where you use your air conditioner) than heating days, a roof with higher shingle reflectivity might be beneficial. However, if you live in Climate Zones 4, 5, 6, or 7 and have more heating days (days where you use your furnace) than cooling days, a roof with higher shingle reflectively might not be as beneficial. Attic air sealing, attic insulation, attic ventilation and solar roofing panels might be areas to consider regardless of where you live if a more energy efficient roof is your goal.
Photo credit: https://basc.pnnl.gov/images/iecc 1
What To Do Next
An experienced roofing contractor can help answer questions you might have about what material to use for your next roofing project. That's why it's so important to choose a knowledgeable roofing professional. The Owens Corning Roofing Contractor Network is made up of independent roofing contractors who've demonstrated their reliability and craftsmanship. You can search by zip code to find one in your area.