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How To Read A Window's Energy Efficiency Label

There are several ways to find out if your current windows are energy-efficient, and we have talked about that in detail here. On the other hand, a new high-quality window that is worth the price you are going to pay for it should be bearing both Energy Star and National Fenestration Rating Council (NFRC)’s labels. Although existing together most of the time, these labels are not one and the same. In this article, we will explain what each of them represents and what it means to have them on a window.

Energy Star Label and Logo

Energy Star

Created back in 1992 by the Environmental Protection Agency and the Department of Energy of the United States of America, Energy Star is now the international standard for energy-efficient products. Consumer products carrying Energy Star logo are widely trusted to save consumers’ money as well as protect the environment by practicing energy-efficiency.

Moreover, Energy Star aims to cut down on greenhouse gas emissions and other pollutants which are related to insufficient energy usage, in addition to simply making it easier for consumers to identify energy-efficient products that offer great performance and comfort.


National Fenestration Rating Council

National Fenestration Rating Council NFRC label

The National Fenestration Rating Council (NFRC) is an American non-profit organization that provides energy performance labeling for windows, doors, and skylights in order to help consumers compare products and make educated decisions when it comes to energy-efficiency.

NFRC Label Components:

NFRC’s current label has been in use since 2005. The label is comprised of the following components;

  • U-Factor

U-Factor represents how well the windows keeps heat and prevents its escape. The lower the U-Factor, the better. It also means that the window can resist heat flow and has a greater insulation value. Check out this article to learn more about U-Factor.
Range: 0.20 – 1.20
What to look for: Low numbers
Tax credit qualification requirement: 0.3 or less

  • Solar Heat Gain Coefficient (SHGC)

This component measures the extent to which a window can block radiant heat coming from the sun. 
Range: 0 – 1
What to look for: Low numbers
Tax credit qualification requirement: 0.3 or less 

  • Visible Transmittance (VT)

Visible Transmittance indicates the amount of visible light that is allowed through the window and how effectively it can light a room. The higher the number, the more natural light that is allowed inside.
Range: 0 – 1
What to look for: High numbers
Tax credit qualification requirement: None 

  • Air Leakage

This component displays the amount of lost and gained heat through the cracks in the window assembly. The lower the number, the less the air that is passing through. Please note that this rating is optional and some manufacturers may not include it.
Range: 0.1 – 0.3
What to look for: Low numbers
Tax credit qualification requirement: None

  • Condensation Resistance (CR) 

Condensation Resistance measures how the window resists the forming of condensation on its interior surface. The higher the number, the better the resistance.This rating is also optional and might not always be included.
Range: 0 – 100
What to look for: High numbers
Tax credit qualification requirement: None

  • C.E.C. Air Infiltration Standards

C.E.C, or the California Energy Commission, is the state’s main energy policy and planning agency. C.E.C advocates for energy-efficiency in appliances and building standards. If a window’s label states that it “ meets or exceeds C.E.C. Air Infiltration Standards”, it means that the window structure complies with the commission's air leakage standards.

  • WDMA

WDMA, or the Window & Door Manufacturers Association, is a trade association that defines window excellence standards. WDMA members produce excellent high-performing windows, doors, and skylights that meet its standards.

  • Hallmark Certified

Hallmark Certification Program helps consumers identify products that meet WDMA’s standards, in addition to being a well-known mark of excellence among architects and contractors alike.

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