For a roof to be energy-efficient in Tennessee, it needs to limit heat from entering your home in warmer months and escaping in cold weather. How well it does both depends on how much solar heat the roof absorbs and releases and how readily heat moves between the attic and living space.
Middle Tennessee’s mixed-humid climate adds another factor. The same reflectance that helps a roof stay cool in July may slightly increase heating costs in January.
This guide from Austermiller Roofing explains how roofing materials, attic ventilation, and insulation work together to affect energy efficiency, how to use CRRC ratings to compare roof coverings and reflective coatings, and how Tennessee’s climate and home-specific conditions influence year-round energy savings.
What Makes a Roof Energy Efficient in Tennessee?
A roof’s energy efficiency depends on how well the roofing surface and the roof-and-attic assembly manage heat year-round. Solar reflectance, thermal emittance, attic ventilation, and insulation are what determine that performance. All four are connected, but none works in isolation. Each addresses a different aspect of heat transfer.
- Solar reflectance: Measures how much solar energy a roof reflects rather than absorbs. A product with higher reflectance generally stays cooler in direct sunlight, reducing the amount of heat available to move into the attic.
- Thermal emittance: Measures how effectively a roof releases the heat it absorbs. High reflectance limits heat absorption, while high emittance helps prevent absorbed heat from remaining at the roof’s surface.
- Attic ventilation: A balanced system of intake and exhaust vents lets air flow through the attic, helping reduce heat and moisture buildup. Learn more about how these systems work in our guide to proper roof ventilation.
- Insulation: Insulation resists heat flow between the attic and conditioned living space. It helps limit heat transfer into your home during warmer months and heat loss during colder weather. Our Nashville homeowner’s guide to roof insulation provides a closer look at how insulation supports year-round energy efficiency, including R-values and common insulation materials.
Solar reflectance and thermal emittance are measurable properties of the roofing product. However, they do not account for ventilation, insulation, or other home-specific conditions, so they cannot predict how much a homeowner will save on energy bills.
To predict savings, the entire roof-and-attic assembly and home-specific conditions must be evaluated. Cool-roof ratings serve a narrower purpose by showing how roof coverings and reflective coatings manage solar heat at the surface.
Cool Roofing Materials and How CRRC Ratings Work
CRRC ratings are product-specific values showing how roofing surfaces reflect sunlight and release absorbed heat. They come from the Roof Product Rating Program administered by the Cool Roof Rating Council, a 501(c)(3) nonprofit organization that develops methods for evaluating and labeling the radiative properties of roofing and exterior wall products.
To produce a rating, a product’s solar reflectance and thermal emittance are tested in accordance with ANSI/CRRC S100. CRRC uses those results to calculate the product’s Solar Reflectance Index (SRI), a single value that indicates its relative ability to remain cool in the sun under standardized conditions. Initial and three-year-aged solar reflectance, thermal emittance, and SRI values are then published in the CRRC Rated Roof Products Directory
A CRRC rating reports surface-performance data, but it does not rank or approve a product, nor does it determine whether it qualifies as cool under a specific code or program. Of the values reported, SRI provides the simplest way for homeowners to compare solar reflectance and thermal emittance in a single number.
How to Read a Solar Reflectance Index Number
When reading an SRI number, look at both the value and whether it is an initial or three-year aged rating. A higher SRI means the roof surface is expected to remain cooler under the same amount of solar exposure.
Most roofing materials have an SRI between 0 and 100, although values outside that range are possible. SRI is not a percentage, so a value of 50 does not mean the product reflects 50% of solar energy.
The CRRC directory reports a product’s SRI at initial testing and again after three years of outdoor weathering. Homeowners should compare initial ratings with other initial ratings or aged ratings with other aged ratings, rather than comparing one product’s initial value with another product’s aged value.
Comparing Cool Roofing Options: Shingles, Metal Roofing, and Reflective Coatings
Roofing products designed to reduce solar heat absorption are available as asphalt shingles, metal roofing, and reflective coatings. Material type matters, but color, finish, surface technology, texture, and weathering create substantial differences within each category. CRRC ratings help homeowners compare individual products.
- Asphalt shingles: Traditional dark asphalt shingles have historically had low solar reflectance, but some newer products improve on that baseline. Reflective granules and specially designed colors can increase solar reflectance, resulting in meaningful differences among shingle lines. According to an April 2024 CRRC analysis, three-year aged SRI values for the asphalt shingles listed at that time ranged from 14 to 34.
- Metal roofing: Metal roofing can achieve higher solar reflectance and SRI values than asphalt shingles, particularly with factory-applied reflective finishes. However, color and coating create considerable variation. The same CRRC analysis reported three-year-aged SRI values from 20 to 90 for factory-coated metal roofing. Because that range overlaps the asphalt-shingle range, choosing metal does not automatically guarantee a higher SRI.
- Reflective coatings: Reflective coatings can increase the solar reflectance of compatible roof surfaces and may be used on some existing roof systems. Suitability depends on the roofing material and the coating’s application requirements. Surface texture can also affect performance, so the CRRC directory identifies whether a coating was tested over a smooth or rough substrate. Some coatings have separate directory entries for each substrate.
CRRC ratings offer one way to compare surface performance, but they don’t account for cost, lifespan, storm resistance, maintenance, or whether a product fits a particular home. Homeowners choosing between metal roofing and asphalt shingles should also consider these factors.
To learn more, our comparison of metal roofing and asphalt shingles examines those broader differences, and our guide to the best roofing materials for hot climates covers how other material options hold up in Tennessee’s heat.
What Happened to ENERGY STAR Certification for Roofing Products?
ENERGY STAR certification for roofing products ended on June 1, 2022, when the Environmental Protection Agency discontinued its Roof Products specification. Before then, qualifying roofing products could earn the government-backed designation by meeting EPA performance requirements. Roofing products can no longer earn or be marketed as ENERGY STAR certified.
Homeowners looking for current product performance data can check CRRC ratings. They do not replace the ENERGY STAR program or serve as an equivalent certification, but the CRRC identifies its Roof Product Rating Program as a potential alternative source of product data for uses such as code compliance and qualification for financial incentives.
What Determines Energy Savings From a Cool Roof?
How much a cool roof lowers an electric bill depends on local climate, insulation levels, air-conditioning use, and utility rates. But at its core, a cool roof limits how much solar heat the roofing surface absorbs.
The U.S. Department of Energy puts a hard number on the temperature difference created by limiting solar heat absorption, reporting that cool roofs can stay up to 60°F cooler than traditional black roofs during summer. Tennessee-specific research further shows how lower surface temperatures can affect heat transfer through a roof assembly.
In a year-long study at Oak Ridge National Laboratory (ORNL), researchers applied reflective coatings to EPDM roof membranes, a type of synthetic rubber roofing, installed on the facility’s Roof Thermal Research Apparatus and measured roof temperatures and heat flow under East Tennessee weather conditions.
The coatings reduced the cooling required to offset heat entering the tested assembly by about 80% compared with a black reference roof and about 33% compared with a white reference roof. However, these percentages refer to specific coatings on a low-slope membrane assembly. They do not mean a Tennessee homeowner’s energy bill will decrease by 80% or 33%. No single percentage can predict that accurately.
According to the Cool Roof Rating Council, estimating household savings from a cool roof generally requires energy modeling that accounts for local climate, insulation levels, air-conditioning use, utility rates, roof assembly, ventilation, slope, orientation, shade, and the difference in reflectance between existing and new roof coverings.
How Tennessee’s Mixed-Humid Climate Affects Cool Roof Energy Savings
In Tennessee, the same reflectance that lowers cooling demand during hot, humid summers can reduce solar heat that warms a home in colder months. With less heat available, the heating system may use more energy, increasing winter heating costs. The Cool Roof Rating Council calls this additional demand a heating penalty.
The heating penalty is usually smaller than the energy saved on cooling over the year, so a cool roof may still reduce total annual energy use. However, the net effect depends on the roof assembly, insulation, ventilation, and heating system.
Research in Tennessee shows why you must consider the complete roof-and-attic assembly when estimating year-round performance. Between 2009 and 2013, ORNL tested several standing-seam metal roof configurations combining rigid insulation, materials designed to store and release heat, surfaces that limit radiant heat transfer, and ventilation beneath the metal panels.
All tested systems reduced heat flow through the roof and ceiling and limited daily attic temperature fluctuations compared with the asphalt-shingle control. However, since each configuration included several features, the results do not show how much improvement came from metal roofing, insulation, ventilation, or any single component.
In a separate field test, ORNL evaluated a roof-and-attic system that paired foil-faced insulation with passive ventilation. The system directed summer heat up and out through an air space above the roof while limiting winter heat loss.
Together, these studies show why reflectance alone cannot predict year-round energy performance. For Tennessee homeowners, potential savings depend on how the entire roof-and-attic system performs during both cooling and heating seasons.
Energy-Efficient Roofing FAQs
Do light-colored shingles improve roof energy efficiency?
They can. Lighter or reflective shingles may absorb less solar heat than standard dark products, but color alone does not determine performance. Compare the product’s solar reflectance, thermal emittance, and SRI values in the CRRC directory.
Is a metal roof more energy efficient than asphalt shingles?
Not automatically. Factory-coated metal can achieve higher SRI values than asphalt shingles, but color and finish affect the rating. Compare specific CRRC-rated products rather than assuming every metal roof will perform better.
Are there rebates for an energy-efficient roof?
Not specifically for residential roof coverings under the current Tennessee programs we could verify. TVA EnergyRight offers rebates for related improvements, including attic insulation, air sealing, HVAC systems, and ductwork. Homeowners should check with their local power company before beginning work because available programs can change.
Will a cool roof lower my power bill in Tennessee?
Energy-efficient roofing can reduce summer cooling costs by limiting solar heat gain through the roof. However, because Tennessee has a mixed-humid climate, annual savings also depend on the roof assembly, insulation, ventilation, HVAC efficiency, and utility rates. These conditions vary, so no set savings percentage applies to every home. For a more accurate estimate, a trusted Tennessee roofing contractor can evaluate the roof-and-attic system, and a qualified energy assessor can use building energy modeling and local weather data to estimate how a roofing change may affect annual energy use.
Get Help Choosing Energy-Efficient Roofing in Middle Tennessee
If you are considering energy-efficient roofing solutions for your home, a local contractor can evaluate your existing roof-and-attic system and explain how different materials may perform in the region’s climate.
Austermiller Roofing was founded and is based in Middle Tennessee. With decades of service to homeowners throughout the area, we understand how local weather affects roofing performance and can help you compare options suited to your home and energy-efficiency goals.
Contact us to schedule a residential roof inspection and discuss energy-efficient roofing options suited to your home.
Sources
Cool Roof Rating Council: Organization and Roof Product Rating Program
Cool Roof Rating Council: ANSI/CRRC S100 Standard
Cool Roof Rating Council: Rated Roof Products Directory
Cool Roof Rating Council: Understanding the Solar Reflectance Index, April 2024
Cool Roof Rating Council: Home and Building Owner Resources
Cool Roof Rating Council: ENERGY STAR Roof Program Alternative
Cool Roof Rating Council: Determining the Energy Savings of a Cool Roof
U.S. Department of Energy: Purchasing Energy-Efficient Cool Roof Products
ORNL: Effectiveness of Cool Roof Coatings with Ceramic Particles
ORNL: Performance Evaluation of Advanced Retrofit Roof Technologies Using Field-Test Data, 2009 to 2013
ORNL: Roof-and-Attic Design Proves Efficient in Summer and Winter
ENERGY STAR: Roof Products Specification Version 3.0
Internal Revenue Service: Energy Efficient Home Improvement Credit
TVA EnergyRight: Current Residential Energy-Efficiency Rebates