Galvalume Roof vs. Using Radiant Barrier Foil: Why They’re Not the Same

If you're getting a new metal roof, you may be wondering:

“If I'm getting a Galvalume roof, isn't it basically the same thing as adding an aluminum foil radiant barrier?”

The answer may surprise you!

What Is Galvalume Roofing?

Galvalume is a coated metal product made from a steel sheet dipped in a mixture of approximately 55% aluminum, 43.4% zinc, and 1.6% silicone. This alloy gives the panel corrosion resistance and some natural reflectivity, making it a popular choice for residential and commercial roofing.

However, Galvalume's primary purpose is protection and durability, not radiant heat control. Its thermal performance is fundamentally different from that of a radiant barrier made from pure aluminum foil.

Reflectivity and Emissivity: The Real Performance Numbers

The key difference between Galvalume and radiant barrier foil comes down to reflectivity and emissivity — two factors that determine how well a material can block radiant heat.

• A typical Galvalume roof surface has a solar reflectance of around 50–55% and an emissivity of 0.80 or higher. This means it reflects only about half of the radiant energy while allowing much of the heat to radiate downward into the attic or living space.

• By contrast, RoofingFoil radiant barrier products are made from 99% pure aluminum bonded to a core for strength. They reflect up to 97% of radiant heat and have an emissivity of 0.03 or lower, dramatically reducing heat transfer into the space below the roof.

Simply put, 50% reflectivity is not the same as 97% — not even close.

Real-World Benefits: Cooler Attics and Lower Energy Bills

A Galvalume roof by itself helps reduce heat gain compared to traditional dark shingles, but a significant amount of radiant heat still enters the structure.

When a radiant barrier is installed underneath the roof panels, attic temperatures can be 20–30°F cooler during the summer. This helps:

• Reduce the load on your HVAC system

• Improve indoor comfort

• Lower energy costs by up to 10–15% in some homes

Long-Term Performance Matters

Another important factor is long-term performance (longevity of the product). Over time, the exposed Galvalume surface can lose reflectivity due to oxidation, dust, and environmental exposure. Radiant barrier foil installed beneath the roof covering is protected from weathering, so it maintains its high reflectivity year after year.

A Galvalume roof alone can help lower heat gain compared to dark asphalt shingles, but much of the radiant energy still passes into the structure.

Adding a radiant barrier can reduce heat gain by 40–50%, lowering cooling loads, improving comfort, and in many cases reducing HVAC run times and energy bills.

Installation Advantages: RoofingFoil™ is Easy to Install During a New Roof Project

When you're installing a new metal or tile roof that's going to have the air gap already in place, incorporating a layer of radiant barrier foil under the panels is quick, affordable, and can deliver benefits for decades. It’s far easier to add it now than retrofit it later and it's a obvious upgrade that shouldn't be overlooked.

Bottom line: A Galvalume roof is not a radiant barrier. While it does offer some reflectivity, it doesn’t match the performance of RoofingFoil™. If you’re investing in a metal roof, upgrading with radiant barrier foil is a smart, cost-effective way to maximize comfort and energy savings.