How Do I Choose An Energy Efficient Window

Here at The Window Man we get a lot of questions about choosing energy efficient windows. How can you tell which windows are a good bet?

Look for products that are tested and approved by the National Fenestration Rating Council (NFRC). This includes testing the U-value of a window. Look for the sticker on the window. Another place to look for information on energy efficiency in windows is: U.S. EPA Energy Star Homes Program web site. NFRC and Energy Star give you a measure of a windows "Thermal Performance Only".

• 1-A. How Should I evaluate structural, air infiltration and other performance issues?

AMA and NWWDA Ratings

American Architectural Manufacturers Association (AAMA)*
National Wood Window and Door Association (NWWDA)*

* Have set test specifications standards for windows and doors

How the Standard Works

The standard defines four mandatory performance requirements for a completely fabricated window:

• Structural integrity to withstand wind loads

• Resistance to Water Leakage

• Resistance to air infiltration

• Forced Entry resistance

Actual windows are tested by independent labs and graded by their "Design Pressure" performance.

The following table shows the minimum Performance Grade required for each class.

Window/Door Performance Grade Structural Test Pressure Water Resistance Pressure Residential (R) 15 22.5 psf 2.86 psf Light Commercial (LC) 25 37.5 psf 3.75 psf Commercial (C) 30 45 psf 4.5 psf Heavy Commercial (HC) 40 60 psf 6.00 psf Architectural (AW) 40 60 psf 8.00 psf

A window rated "R" 15 just passed for residential use only.
An "R" 30 or 45 rated window will perform much better.