What is a Cool Metal Roof?

Published August 11, 2017 by Whirlwind Team

cool metal roof

A cool metal roof is a cool way to go green. It can save you money and help the environment at the same time. How cool is that?

Cool metal roof systems are an essential element in energy-efficient buildings, providing benefits and advantages to both the building owner and the surrounding community. A cool metal roof has the second benefit of incredible durability and strength for its weight because it is made of steel.

Let’s dig into the definition and terms you will come across in the cool metal roof industry, expand on the benefits, and slay a few myths while we’re at it.


What is a “cool metal roof?”

A cool metal roof is not one that is cool to the touch, although it is cooler than a traditional roof. A cool roof is a roof that is designed to reflect and re-emit the heat from the sun.

Terms to know:

  • Emissivity describes the act of emitting - radiating - the heat from a surface. A high emissivity indicates a high amount of heat is radiated.
  • Reflectivity describes the act of reflecting heat directly away from an object. A high reflectivity indicates a high amount of heat is reflected.
  • Urban heat island is formed when heat radiated from concrete, asphalt, and other materials gathered in close proximity, as with a heavily populated urban area, actively raises the temperature within that area above that expected from natural sunlight.

An asphalt roof is typically a darkly colored material that soaks up the heat like a reptile and retains it for a time, even after the sun has gone down. The heat soaks into the building below the roof and gives off heat into the nearby area throughout the night.

As the indoor temperature rises, more electricity is used for cooling. Additional cooling is also needed during the night time hours when the heat only slowly dissipates after dark and heats the surrounding area. If there are many asphalt roofs in a limited space, a heat island can develop.

A metal roof directly reflects the heat created from solar energy hitting the roof panels; the roof does not absorb the heat as asphalt does. If the metal roof is coated in a white or very light finish, the heat is also re-emitted back into the atmosphere quickly. Heat is not absorbed, stored, and slowly leached into the air overnight.

Benefits of a cool metal roof

The biggest advantage is the energy savings from reflecting and re-emitting heat away from your building. If the heat doesn’t soak into the building, less air conditioning is required to keep it cool.

Since the heat is not slowly emitted into the air overnight, the surrounding community remains cooler as well, holding down energy costs and generation peaks at night. The heat island never forms.

With lower heat values, you also:

  • Reduce smog
  • Reduce peak energy use
  • Reduce carbon emissions

Cool metal roofs are extremely durable. Most pests can't chew their way into a metal roof panel, and properly coated steel will not corrode.

A metal roof of any color can get you an insurance discount because it is both fire and hail resistant. Plus, with the variety of colors, textures, and appearances, your metal roof can look like any type of roof. A cool metal roof is simply one that is coated with a white surface or other very light color. Some coatings contain additional elements to enhance reflectivity.

Myth-busting metal roofs

  • Myth 1: Metal roofs are ugly and noisy. No and no. Metal roofs can be made to look identical to any roof color, texture, or appearance. All have an underlayment that softens and prevents sound from penetrating into the structure.
  • Myth 2: Cell phones won’t work with metal roofs. If you have cell phone reception inside a store, office building, or any other structure primarily constructed of steel, a metal roof won’t stop you either.
  • Myth 3: Metal roofs are expensive. While a metal roof can cost more up front, its decades of durable service without the need for replacement coupled with low maintenance make metal roofs a steal.
  • Myth 4: Poor performance in moist environments. Also not true. A properly coated and installed metal roof is durable in any environment. As long as appropriate maintenance is performed and the roof is sloped for good run-off, a metal roof still outperforms a traditional roof over the course of its life.

Get your free copy of our Metal Roofing Guide today »

The Cool Roof Rating Council

The Cool Roof Rating Council, established in 1998, is an independent non-profit that measures and rates roofing product surfaces for radiative properties. It is made up of two completely separate groups: the licensees group and the member group.

  • Licensees are those that rate roofing products or components.
  • Members are parties interested in the CRRC organization and who may actively participate on the board and vote on matters of interest to the organization.

Metal roofing manufacturers can ask for their products to be tested in the CRRC’s labs to measure their radiative properties and obtaining a rating that gives consumers an independent, third-party verification of the energy performance of different roofing materials.

The CRRC also supports research and education for energy-efficient roof materials.

With the steady move toward green building and the desire for LEED ratings, manufacturers, architects, and builders rely on the CRRC for expert evaluations and ratings toward LEED points.

Manufacturers can get both initial and aged ratings from a test farm location to measure the changes in performance over time due to pollution, algae growth, and weather conditions. The Aged Rating is a measurement of performance after three years of installation.

The CRRC publishes a product directory that users can search by a variety of categories including product type, manufacturer, roof slope, initial and aged performance, and more.

One of the organization’s goals is to increase the use of recycled materials. Today’s steel is made up of both new steel and recycled steel. Steel is 100% recyclable itself. Steel should never make its way to a landfill.

Opting for a cool metal roof is a move toward energy efficiency and decreased environmental impact. Whether you agree the climate is changing or not, taking care of the environment is the right thing to do. With a cool metal roof, you can do your part while reducing your electricity use and your insurance, lowering the ambient air temperature, and owning a long-lasting, durable, low-maintenance roof.

Metal Roofing Guide



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