Energy Efficient vs Energy Star Windows
Tucson homeowners looking for window replacements often ask us, “what’s the difference between an energy efficient window and an Energy Star qualified window?”
This is a tricky question, but in short our response is this: an Energy Star qualified window is an energy efficient window, but an energy efficient window isn’t necessarily Energy Star qualified.
Before we go further in detail about the contrast between the two, it’s best you first understand the reasoning behind the establishment of the Energy Star label that you see on many windows today.
First off, the “Energy Star” is a government-backed symbol, developed by the EPA, that delineates energy efficiency in order to help consumers easily identify products (windows in this case) that save them money as well as protect their environment.
The idea behind labeling windows as Energy Star qualified is that if enough people purchase them, then we can reduce greenhouse gas emissions, and other pollution, generated from inefficient, though similar, windows.
How Does a Window Earn the Energy Star?
The window must meet specific energy efficiency requirements as well as follow a certain principles defined by the EPA.
Those are as follows:
– Windows must show significant energy savings.
– Windows should increase energy efficiency as well as maintain other features and performance factors demanded by consumers.
– Windows that cost more than conventional substitutes should allow consumers to recover those costs through energy bill savings, and within a reasonable time period.
– Windows must achieve increased energy efficiency through widely obtainable technologies offered by more than one manufacturer. This means patented or trademarked technologies that increase energy efficiency aren’t qualified.
– Windows’ increased energy efficiency must be verifiable through testing.
– Windows labeled with the Energy Star must make the symbol visible to consumers and the symbol must effectively differentiate the windows from similar less efficient ones.
Other Restrictions Include:
– Windows must be manufactured by a certified, Energy Star partner.
– Windows have been independently tested and certified by the National Fenestration Rating Council (NFRC).
– Windows must meet strict NFRC energy efficiency ratings set by the U.S. Department of Energy (DOE).
Okay, we get it – there are strict rules that allow windows to be Energy Star qualified, but what’s the difference?
The difference between your regular old, energy efficient window and an Energy Star qualified one is that the Energy Star window is NFRC certified, and has superior energy efficiency compared to other windows (including other NFRC certified ones).
How Can They Tell What Windows Are Superior Though?
The NFRC rates window performance based on five different factors:
– Solar Heat Gain Coefficient (SHGC)
– Visible Transmittance (VT)
– Air Leakage (AL)
– Condensation Resistance
The most important of these – the U-Factor and the SHGC – are in fact the only ratings that Energy Star honors in their qualifications. The U-Factor essentially measures the rate of the heat transferred through the window, or rather how well the window insulates.
The SHGC though, is what’s most crucial to windows in Tucson homes. SHGC measures the percentage of solar heat transmitted through the window, or rather how well the window blocks out heat caused by sunlight.
The lower the SHGC, the less heat your windows let into your home from outside. Depending on window frames and manufacturing features, your window replacement’s U-Factor could vary from .25 to .60; however, you should note that windows best suited for Tucson homes will have a SHGC less than .30.
Again, in our climate, the SHGC is FAR more important than the U-Factor. That being said, you should be happy to hear this: American Openings Windows offers Energy Star qualified windows with SHGC’s as low as .20!
So there you have it! Now you know the difference between an energy efficient window and an Energy Star qualified window. Energy Star qualified windows are far superior in energy efficiency and meet strict energy performance ratings provided by the NFRC.
For more information: American Openings’ Windows NFRC ratings