What Is Cool Roofing?
On a hot afternoon, two identical houses can feel completely different inside — and the difference is often what’s reflecting, or absorbing, the sun overhead.
A “cool roof” is simply a roof engineered to bounce solar energy away rather than soak it up. Dark asphalt absorbs most of the sunlight that hits it and radiates that heat down into the attic; a reflective surface sends much of it back to the sky. The result is a cooler attic, a lighter load on your air conditioner, and the savings we cover in metal roof energy efficiency.
Cool performance is measured, not marketing. The Cool Roof Rating Council (CRRC) has tested products for two decades on two numbers — solar reflectance and thermal emittance — and energy-efficiency sets the bar a roof must clear to qualify. Interlock’s aluminum roofing clears it, and does so in real colors, not just white.
Interlock’s Alunar® finish is independently tested with solar reflectance up to 0.55 and thermal emittance of 0.84.
What is cool roofing?
Cool roofing is roofing engineered to reflect sunlight and release absorbed heat quickly, measured by two values: solar reflectance and thermal emittance. The Cool Roof Rating Council (CRRC) tests both. Interlock’s Alunar® aluminum finish qualifies as a cool roof — with solar reflectance up to 0.55 and thermal emittance of 0.84 — so it keeps homes cooler and cuts cooling-energy use by up to 25%.
What Makes a Roof a “Cool Roof”
Two measured properties define cool roofing. Solar reflectance is the fraction of sunlight the surface bounces away (0 to 1 — higher is cooler). Thermal emittance is how readily the surface releases the heat it does absorb (also 0 to 1 — higher means it cools down faster). A genuine cool roof scores well on both. The Cool Roof Rating Council has independently rated these values for more than 20 years, and energy-efficiency uses them to set the minimum reflectance a roof must meet to earn the label. It’s an objective standard, not a sales claim.
Why Interlock Qualifies as a Cool Roof
Interlock’s Alunar® PVDF finish is engineered specifically for reflectance and is independently tested for steep-slope cool-roof performance. Independent testing lists solar reflectance from 0.25 up to 0.55 (the Aged Copper Penny color is highest) and a thermal emittance of 0.84 — and that reflectance is warranted for 40 years. Aluminum helps on both counts: it reflects well and re-emits heat quickly, so an Interlock roof doesn’t hold the afternoon’s heat the way a dense asphalt mat does. One Washington State homeowner reported a 10°F drop indoors immediately after switching to an Interlock roof.
Cool Roofing Isn’t Only White
The biggest myth about cool roofs is that they must be white or pale. Modern reflective coatings like Alunar® use pigment technology that reflects a large share of the sun’s near-infrared energy — the part you can’t see but that carries most of the heat — even in darker colors. That means you can choose a Deep Charcoal slate or a Copper Penny shake and still get meaningful cool-roof performance. You don’t have to compromise the look of your home to get the energy benefit.
The Benefits: Savings, Comfort, and Color
A cool roof pays you back in three currencies. Lower bills: reflecting solar heat can cut cooling-energy use by up to 25%. More comfort: upstairs rooms and west-facing spaces stay noticeably cooler in summer, and the air conditioner cycles less. And design freedom: because Alunar® performs across the palette, you keep full control of curb appeal. It’s the rare upgrade that lowers your operating cost without asking you to settle on appearance.
Cool Roofs and the Environment
Cool roofing scales from the single home to the city. Across a metro area, dark roofs and pavement create the urban heat-island effect — measurably higher temperatures and energy demand; in Los Angeles alone the effect is estimated to cost about $100 million in energy per year. Reflective roofs help push back. Interlock adds a second environmental win: the panels are made largely from recycled aluminum and are 95% recyclable, and recycling aluminum uses only about 8% of the energy of producing it new. Read more in investing in a sustainable future.
Is a Cool Roof Right for You?
If you pay to cool your home for any meaningful part of the year, a cool roof is one of the few upgrades that starts paying back immediately and keeps doing so for decades. With Interlock you get cool-roof performance, a full color range, and the durability of a lifetime aluminum system in one package. Explore what it means for a roof to be “solar friendly,” or request a free quote to see the numbers for your home.
Frequently Asked Questions
What is a cool roof?
A cool roof reflects sunlight and releases absorbed heat quickly, keeping the building cooler. It’s measured by solar reflectance and thermal emittance, rated by the Cool Roof Rating Council (CRRC).
How does a cool roof save money?
By reflecting solar heat away from the attic, a cool roof reduces cooling-energy use — up to 25% for a reflective metal roof — lowering summer utility bills and easing wear on your air conditioner.
Do cool roofs only come in white?
No. Interlock’s Alunar® finish reflects near-infrared solar energy even in darker colors, so you get cool-roof performance in shades like Deep Charcoal or Copper Penny, not just white.
What are Interlock’s cool-roof numbers?
Interlock’s Alunar® finish is independently tested with solar reflectance from 0.25 to 0.55 (by color) and a thermal emittance of 0.84, with the reflectance warranted for 40 years.
Does a cool roof help in winter?
Cool roofs are optimized for cooling-season savings. In winter a metal roof still performs well — shedding snow and resisting ice dams — and works alongside attic insulation year-round.
What is the CRRC?
The Cool Roof Rating Council is an independent body that has tested and published solar reflectance and thermal emittance values for roofing products for over 20 years, providing the standard cool-roof metrics.
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Last updated June 8, 2026 · Reviewed for accuracy by the Interlock SEO Desk.