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The Most Efficient Windows:

This government website,, provides a list of the most energy efficient windows along with the performance grade (PG) of each window.


NFRC ratings:

The National Fenestration Rating Council (NFRC) rates the majority of all windows before they can be sold to the public. If a company cannot provide you an NFRC rating, do not purchase that window. If you have a salesman who is not being transparent with his window's ratings, you can look them up yourself by utilizing the following website! Make sure that you have the window's CPD number to ensure it is the window you are contemplating.

NFRC has an online directory of all the windows they have rated available for free at:

About NFRC:

The National Fenestration Rating Council (NFRC) rates the energy performance of windows, doors, and skylights. These ratings can be a valuable comparison tool because they help you to:
- Compare different products on an apples-to-apples basis
- Make sure that a product will perform as it should by verifying information
- Make an informed choice about a substantial investment that will stay in your home for many years

The NFRC Label:

The NFRC label, such as the one shown below, provides homeowners with the key energy performance metrics on any window. Want the easiest way to compare window performance? Ask to see the window's NFRC sticker!

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This is a slightly cumbersome website with great technical data for most single replacement windows sold on the market. Always ask for the CPD number given to the specific window recommended to you; and look that up on 

Replacement Window Forum

The following window forum allows homeowners to ask window professionals questions in a public forum.

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