What Is a Cool Roof?

graphic showing how a cool roof works

The notion that lighter colors reflect sunlight while darker colors absorb it is not new. Traditional asphalt shingle roofs can reach extreme temperatures 80 degrees higher than the outside air, and with nowhere to go, the heat penetrates your home. Today, many cool roof varieties exist to reflect the sun’s rays and stop heat transfer. But what exactly is a cool roof? 

Discover how you can benefit from a cool roof and start saving between 7% to 15% on your annual energy costs. 

What Is a Cool Roof?

A cool roof is less a type of roof and more a collection of roofing materials that all share the same properties. 

  1. It absorbs less heat.
  2. It reflects more sunlight.
  3. It reduces energy consumption.

Cool roofs are not a new concept, and thankfully, we no longer have to rely on white roofs to get the job done. Cool roofing materials and coatings lower a roof’s surface temperature and decrease heat transfer

These roofs strongly reflect sunlight, or solar energy, through solar reflectance (SR), and efficiently emit absorbed heat, or infrared radiation, through thermal emittance (TE). To be classified as a cool roofing material by the Cool Roof Rating Council (CRRC), the cool roof product must possess both high solar reflectance and high thermal emittance over a three-year testing period. 

Solar Reflectance Index (SRI)

The U.S. Green Building Council uses the Solar reflectance Index (SRI) to evaluate all cool roofing materials. SRI combines solar reflectance and thermal emittance into one standardized measure. 

SRI is determined through a complex equation and uses a scale of zero to 100. Black roofs with no reflective properties start at zero, while reflective white roofs have a value of 100. Common asphalt shingles with reflective granules sit at a value between 21 to 30 on the SRI scale.

The higher your SRI value, the more sunlight your roof reflects, lowering the surface temperature of your roof and reducing the heat transfer into your home.

Types of Cool Roofs

cool roof
Photo Credit: Idaho National Laboratory / Flickr / CC BY 2.0

Cool roofs work on both residential and commercial buildings, including flat and low-sloped roofs. Reflective roofing materials and cool roof coatings can be light-colored, but today, many dark-colored options are available. 

Roof options and cool-colored products include: 

  • Membranes: built-up roofing, single-ply membranes, PVC, TPO, EDPM
  • Shingles: asphalt shingles
  • Slate
    • Composite: shingle, shake
  • Metal: standing seam, stamped tile metal roofing, stone-coated steel
  • Tile: clay, concrete
  • Wood: cedar shingle
  • Foam: foam core tile
  • Reflective coatings: paint, asphalt shingle granules, silicone, acrylic, polyurethane, aluminum, SEBS, Urethane, Latex
  • Green Roofs

Pros and Cons of Cool Roofs

What’s in a name? With cool roofs, literally everything. As the name suggests, cool roofs keep your home cooler, stabilizing room air temperatures. 

These roofing systems are energy efficient and durable. While they decrease the rate of smog formation and improve air quality, they might increase winter heating requirements and ice dam formation. 

Benefits of Cool RoofsDrawbacks of Cool Roofs
✔ Reduced utility costs
✔ Increased indoor comfort and temperature stability
✔ Reduced air conditioner and roofing material deterioration
✔ Lowered peak energy demands
✔ Reduced air pollution
✔ Reduced urban heat island effect
✘ Lighter colors show dirt, algae, and moss
✘ Increased winter heating requirements
✘ Increased susceptibility to mold and algae growth
✘ Susceptible to moisture accumulation and ice dam formation

Is a Cool Roof Right For Your Home?

Your roof protects your family from the elements. While durability is a key component in your roofing decision, you don’t have to sacrifice energy efficiency, comfort, or curb appeal.

Roof replacement provides the greatest return on investment of any home improvement project according to the NAR, and you can recoup 100% of your investment while increasing your home’s value, boosting your curb appeal, and lowering your monthly energy bills. 

A new cool roof does not cost more than its “non-cool” counterparts. If you need a new roof, strongly consider a cool roof to save on your annual energy costs. If it isn’t quite time to replace your roof, you have the option of adding a cool roof coating to your existing roof, depending on your roof’s material. 

Ultimately, when deciding whether cool roofing materials are right for your home, consider the following factors: 

  • Budget: Cool roofing materials are not more expensive than other options. However, there is a wide range of price points for roofing materials that qualify as cool roofing options. 
  • Location: Cool roofs provide the most benefits to homes in warmer climates.
  • Projected energy savings: A professional roofing contractor can help you determine your annual energy savings when installing a cool roof.   

FAQ About Cool Roofs

Do cool roofs qualify for incentives or rebates? 

The Environmental Protection Agency and the Department of Energy have teamed up to promote energy efficiency, offering location-based rebates and loans to homeowners and businesses for cool roofing materials. Some locations also require cool roofs in new construction.

What is the average change in indoor temperature after installing a cool roof?

Cool roofs reduce energy use and stabilize room temperature. Compared to traditional roofing materials, they can reduce indoor temperatures between 3.5 to 9 degrees Fahrenheit. 

Do cool roofs work in cold climates? 

Yes. While cool roofs rely on thermal emittance and solar reflectance to keep a home cooler in the summer, those are not the only properties a roof needs to perform well in extreme climates. Factors like insulation, roof orientation, and pitch all affect your home’s thermal efficiency.

Cool Roof Installation Next Steps

According to NASA, 2020 tied 2016 as the hottest year on record, and it wasn’t even an El Niño year, also known as a period of warming in the Pacific Ocean. As climate change continues to affect our surrounding temperatures, that doesn’t mean we can’t be comfortable inside our homes while saving money.  

If you are in the market for a new roof and want to reduce your air conditioner’s workload, contact a local roofing pro to learn about cool roofing materials and start saving on your energy bills. 

Main Image Credit: Illustration by Juan Rodriguez for RoofGnome

Kimberly Magerl

Born and raised in Springfield, Illinois, Kimberly Magerl enjoys growing fruits and vegetables in her garden. When she isn't gardening, Kimberly enjoys trying new recipes and cooking with her home-grown herbs.