Steel Exterior Doors - Numbers (and Measurements) to Know

January 02, 2010

Certainly steel exterior doors are considered one of the most durable, affordable and low maintenance exterior doors available. But not all steel exterior doors are built alike. There are some ratings and numbers to check to make sure your getting the steel exterior door that's perfect for your needs.

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The gauge in steel exterior doors refers to the thickness of the steel 'skin' as it's often called. The lower the number, the stronger the steel skin is. Gauge is technically how many layers of the material would need to be stacked to make an inch. Many premium steel exterior doors are made of 24 gauge steel. That means it would take 24 layers of it stacked to make one inch.


U-factors are indicators of heat transfer. They're expressed in units and a lower U-Factor indicates more energy efficiency. U-factors are important when it comes to getting a steel exterior door that is rated as an Energy Star by the US Federal Government. Energy Star products may qualify for tax credits. U-factor values are expressed in numbers from .20 to 1.20 and lower is better, as it means the product is more resistant to heat flow, thus more energy efficient.

Solar Heat Gain Coefficient (SHGC)

The SHGC is another aspect of the Energy Star rating. It's expressed as a value between 0 and 1, as it's a ratio of solar heat gain entering the space due to the door vs. normally occurring solar heat gain. Smaller numbers are better in the SHGC in terms of energy efficiency.

Know your numbers and the facts when shopping for steel exterior doors - making a more informed decision gives you the most added value for your home or business.

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