Cool Roof & Solar Reflectance: Interlock's Energy Star Values
Quick answer
Interlock's Alunar-finished aluminum roofing is a cool roof. Its colors carry independently measured solar reflectance from about 0.25 to 0.55 and a thermal emissivity of 0.84, and were listed as steep-slope ENERGY STAR–qualified roofing. Reflecting more sunlight and radiating away absorbed heat keeps your attic cooler and cuts summer cooling costs.
What makes a roof a "cool roof"?
On a hot day, a dark, absorptive roof can reach 150–190°F, pushing heat into the attic and forcing the air conditioner to work harder. A cool roof does the opposite: it reflects more of the sun's energy and sheds the heat it does absorb. Two measured numbers define it. Solar reflectance is the fraction of the sun's energy a surface reflects, on a 0-to-1 scale — higher is cooler. Thermal emissivity is how efficiently a surface radiates absorbed heat back out, also 0 to 1 — higher sheds heat faster. A true cool roof pairs high reflectance with high emissivity, which is exactly what Interlock's Alunar finish does.
Interlock's verified reflective values
These are not estimates. Interlock's Alunar colors were independently tested and listed on the ENERGY STAR Roof Product List for Interlock Roofing Ltd., qualified for steep-slope roofs, with a 0.84 emissivity across every color. Solar reflectance varies by shade: Aged Copper Penny is highest at 0.55 initial, followed by Commercial Red at 0.40 and the grey tones around 0.37, down to 0.28 for charcoal and 0.25 for black. The values are consistent across the Shake, Shingle, Slate, Standing Seam, and Tile profiles, so you can choose the look you want without giving up cool-roof performance — and even the darkest colors keep the high 0.84 emissivity that helps the roof shed heat quickly.
What does a cool roof actually save?
A reflective roof reduces the heat entering your home through the roof deck, lowering the summer cooling load. Interlock reports homes running up to about 25% cooler with its cool-roof colors, translating into lower air-conditioning use during the months that drive your electric bill. The effect is largest on sunny roofs in warm climates, on homes with living space directly under the roof, and where attic insulation is modest. Because Interlock installs over your existing roof and the reflective finish is engineered to last decades, the cool-roof benefit does not fade after a few summers the way a cheaper coating can.
A note on tax credits and rebates
It is worth being precise. The federal Energy Efficient Home Improvement Credit (Section 25C) expired on December 31, 2025, and roofs were not an eligible improvement under it — so there is no federal tax credit for a cool metal roof in 2026. However, some state, local, and utility programs still offer rebates for reflective or cool roofing, so it is worth checking with your electric utility. See Interlock's tax credits and incentives page for current details.
Frequently Asked Questions
Is an Interlock metal roof a cool roof?
Yes. Interlock's Alunar-finished aluminum roofing qualifies as steep-slope cool roofing, with independently measured solar reflectance from about 0.25 to 0.55 and thermal emissivity of 0.84, depending on color. Reflecting more of the sun's energy keeps the roof — and the attic beneath it — cooler in summer.
What is solar reflectance and emissivity?
Solar reflectance is the fraction of the sun's energy a surface bounces away (0 to 1, higher is cooler). Thermal emissivity is how efficiently a surface releases absorbed heat (0 to 1, higher sheds heat faster). A cool roof combines high reflectance with high emissivity.
Which Interlock color is the most reflective?
Among the listed Alunar colors, Aged Copper Penny has the highest initial solar reflectance at 0.55, followed by Commercial Red at 0.40 and the grey tones around 0.37. Even the darkest colors carry a 0.84 emissivity, and all Alunar colors share the same durable finish system.
Do cool metal roofs qualify for a federal tax credit in 2026?
No. The federal Energy Efficient Home Improvement Credit (Section 25C) expired December 31, 2025, and roofs were not eligible under it. Some state, local, and utility programs still offer cool-roof rebates, so check with your utility. A cool roof's main financial benefit is lower year-round cooling costs.
Sources
- ENERGY STAR Roof Product List — Interlock Roofing Ltd. Alunar values — Steep-slope solar reflectance & emissivity
- U.S. EPA / ENERGY STAR — Federal Tax Credits for Energy Efficiency — 25C status and expiration
- Cool Roof Rating Council (CRRC) — Rated Products Directory — Current cool-roof ratings
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Last reviewed 2026-07-11 · Reviewed by Scott Plumptree, Director of Marketing