If you wonder about fenestration we have complied a range of information all about windows, glass and fenestration here for you to review. We believe an educated buyer is best, so to help you find out about how fenestration is rated, we gathered to gather all the information from various official bodies to make life a little easier.

You can also check out the other pages under this section in the sub menu above such as Fenestration 101 – a beginners guide, some handy resources or ratings systems and much more!

Shopping Guide

It is easy to become overwhelmed by the vast number of product choices and all the numbers being thrown around about how each window performs. Before you ever start shopping for windows you need to know what you want from your windows. On this page we have provided the tools and information to help you be an informed consumer when shopping for new windows.

How do I Find an Efficient Window?

In today’s market, consumers are often overwhelmed by the many choices of window products. What is the best way to choose windows, doors, and skylights for homes?

1. Look for the NFRC Label

shopping-guide-windowsThe National Fenestration Rating Council (NFRC) is a nonprofit organization whose goal is to provide uniform, accurate information about the energy performance of windows, doors, and skylights. In addition to publishing consensus standards (for consistent ratings), NFRC administers a third-party certification and labeling program to provide the window buyer with verified product information.

So look for an NFRC label on windows to compare products on a fair and equal basis (see Energy Ratings page for a Sample Label and additional information about the ratings).

2. Compare Product Performance

The NFRC label provides information on how a window performs. The two most referenced energy ratings are U-factor and Solar Heat Gain. By reviewing the label information, consumers can make an informed choice about the product that is best for their individual situation.

3. Look for Highlighted Label the ENERGY STAR® Label

NFRC_LabelExample_HighlightedThe U.S.Department of Energy and the U.S. Environmental Protection Agency have developed an ENERGY STAR designation for products meeting certain energy performance criteria. Since the energy efficiency performance of windows, door, and skylights can vary by climate, product recommendations are given for four climate zones: a mostly heating zone (Northern), two heating and cooling zones (North/Central and South/Central), and a mostly cooling zone (Southern). For more information about ENERGY STAR windows, see

Meeting Energy Codes

Since the 1970s, energy code requirements have been established for windows in both residential and commercial construction.

Every energy code provides regulatory, prescriptive, and system or design requirements.

Shopping-trolleyRegulatory requirements include referenced test methods and standards (i.e., NFRC), as well as any certification and labelling requirements

Prescriptive requirements include the fenestration product minimum performance criteria (U-factor, Solar Heat Gain) based on climate zones. In addition, some energy codes provide trade-offs allowing more fenestration area if these products are more energy efficient.

System or design requirements are typically computational approaches allowing builders and architects to customize buildings and use more and or different fenestration products and still meet the energy code requirements through improvements in other areas such as lighting, HVAC system, or other building envelope components.