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Understand Energy and Efficiency Rating for Windows

Understand Energy and Efficiency Rating Before You Shop for Vinyl Replacement Windows At Heart House we understand that your home improvement dollars...
Tuesday, 31 March 2015
Understand Energy and Efficiency Rating for Windows

Understand Energy and Efficiency Rating Before You Shop for Vinyl Replacement Windows

At Heart House we understand that your home improvement dollars are limited and that your priority as a homeowner is to always make sure you get what you expect when you pull out your wallet. We want you to understand exactly what you are getting when you consider purchasing replacement windows for your home in or around Colorado Springs.

New windows, as I’m sure you know, are much more than two ordinary pieces of glass held together in a frame like they were in the distant past. However, you may not realize that windows have evolved even over the past few years as research and development have delivered more efficient products to the home improvement marketplace. Modern window glass is actually quite high tech so they do a lot more for your older home than provide a nice windbreak with a view.

Along with the advanced technology of today’s replacement windows has come industry standards and measurement rating to guide consumers in their replacement window selection. I’ve written this article to help you understand the rating so that you’ll know what to look for in quality replacement windows, and what you want to steer away from, when the time comes for you to invest your home improvement dollars in projects that make the most difference for your and your family.

Window Ratings: Where They Come From and What Those Ratings Mean for Consumers

When you are in the market for new windows, it can be tempting to believe everything you hear from one of the “experts” in the field whose one and only goal is to sell you their product regardless of how well it fits your needs or expectations. However, as a longtime, trusted Colorado Springs window contractor I know that my business depends on happy customers and positive word-of-mouth advertising to stay in business. That’s why I always first explain to homeowners who are looking at replacing their old, inefficient windows the U Factor and other ratings for energy efficiency that they will encounter while shopping around.

U Factor ratings were developed by the National Fenestration Ratings Council (NFRC) as a way to measure a window’s energy efficiency, using four different criteria. Fenestration, by the way, is just a fancy name for windows. All windows are given a rating between 1 and 3, with the lower numbers being representing better efficiency, to make it is easy for consumers to make meaningful comparisons between their replacement window choices.

You may be familiar with the U.S. government’s Energy Star ratings from the last time you purchased a new refrigerator or washer and dryer. In the window industry, the only windows that meet the standard for an Energy Star efficiency rating are those that also meet NFRC standards for energy savings.

Just like the appliance industry has made improvements in the efficiency of their products, the replacement window industry has made remarkable progress in building products that can help to decrease the amount of energy it takes to heat and cool your home.

But not all replacement window contractors offer the same quality of window, which is why it is important to understand the ratings before making a decision on replacement windows that a homeowner will most likely have to live with for many years to come.

Many Colorado Springs window contractors will sell thermal replacement windows without ever discussing the U-Factor ratings, but as a consumer you should always ask for these numbers before deciding what you will buy. If a contractor tries to tell you that ratings don’t matter or that all replacement windows are alike, walk away.

While we can all agree that modern windows are far and away more efficient than the original windows in homes more than a few decades old, all window manufacturers are not created equal. That’s why we rely on Siminton Windows as our source for high-quality, energy efficient windows that are beautiful, functional and add immediate curb appeal to our customer’s homes.

The NFRC ratings are done in the following areas:

U-Factor — Similar to the R-Factor rating on home insulation, the U-Factor, sometimes called a U-Value, measures the amount of non-solar heat loss that occurs through the window. Values for U-Factor range from 0.15 to 1.20. The lower the number the more efficient the window because it has more insulating ability.


Solar Heat Gain Coefficient — Measures the level of “heat gain” during the summer months. Solar radiation that passes through windows is measured in terms of its solar heat-gain coefficient, or SHGC.  SHGC ratings are a useful way to quantify the energy efficiency of windows. Whereas the U-Factor is used to quantify the amount of non-solar heat that passes through a window or skylight, the SHGC quantifies the amount of solar heat that passes through the window. SHGC ratings have a value between 0 and 1, with 1 being the maximum amount of solar heat passes through the window and 0 being the least. An SHGC rating of .30 means that 30 percent of available solar heat is able to pass through the window.

While it may seem like the only correct choice would be to choose the windows with the lowest SHGC rating, that is not always the case.

Homes in Florida, for example, have very different requirements than homes in North Dakota do and a home that has numerous south-facing windows will have different needs than one that can’t rely on passive solar energy for warmth. No window replacement contractor in Colorado Springs knows more about finding the correct windows for our Front Range customers than the professionals here at Heart House.


Air Leakage (AL) — This refers to the window assembly and not the glass. The Air Leakage rating is based on the measurement of air that passes through leaks in the window assembly in terms of the number of cubic feet of air that a square foot of window area. A rating of .30 or less is required for a window to achieve an Energy Star rating, so if you don’t see the Energy Star symbol on the windows you are considering as replacements for your old, inefficient windows, you know that they have too high an AL rating.

Condensation Resistance (CR) — A CR rating is a measurement telling us how well a window resists the formation of condensation on the inside surface of the window. CR values from 1 to 100 are based on interior surface temperatures at 30%, 50%, and 70% indoor relative humidity for a given outside air temperature of 0° Fahrenheit under 15 mph wind conditions. Unlike the other energy ratings that apply to windows, a high number is a good thing when it comes to condensation resistance.

Visible Transmittance (VT) — measures the amount of light that can pass through a window, and has less to do with energy efficiency than with homeowner preference (VT) is an optical property indicating the fraction of visible light transmitted through the window. Spectrally selective coatings on quality modern replacement windows permit different amounts of visible, infrared and ultraviolet light. The higher the VT rating, the more light passes through.

As you can see, a lot goes in to determining the best replacement window for any give house. As Colorado Springs window contractor, I encourage my clients to look at all of the relevant NFRC ratings, as each of them play a role in determining which type of window is best for their needs.

Read 2026 times Last modified on Monday, 22 June 2015