One of the most asked frequently questions we get from all types of individuals is: Is your window Energy Star approved? Everyone gets frustrated by the answer: yes, but, it depends on your location. Usually the next sound from the questioner is…ugh, can’t you just give me a simple yes or no answer? Well… the answer to that question is: UGH, no…sorry about that, Chief!! (: An old “Get Smart” reference”.
Salespeople and homeowners get frustrated by that line of communication. The purpose of this article is to try to shed a little more light onto the question of whether or not a product can qualify for Energy Star ratings. Because it is the most important part of the issue, I will focus on how the U-value is determined.
If you want to cut to through the chase, just read this paragraph and click to your next subject of interest: MGM meets Energy Star. We have tested our windows at MGM in accordance to the NFRC rating standards. Our windows can comply with the Energy Star requirements. So, the question is not: does your window meet Energy Star ratings? A better question is: which configuration of MGM Industries windows meets Energy Star ratings for the Asheville, NC market? Or which ever city you live in. If you want to know more…
First, Energy Star is a program created by the United States Environmental Protection Agency (EPA). It is now a program jointly administered by the EPA and the Department of Energy (DOE) in the attempt to provide a standard by which consumers can compare and contrast various products as it relates to energy usage. It is a voluntary labeling program designed to identify and promote energy efficient products. The program has been around since 1995 but gained traction in the window and door arena in 2010 with the advent of the $1,500 energy tax credit. This credit was granted to consumers who had energy efficient windows and doors installed during the 2010 tax year. Below is how the standard was created and how it is administered.
The EPA decided to have the National Fenestration Rating Council (NFRC) develop a standard by which to measure all energy performance of windows, doors and skylights. NFRC is a non-profit organization that administers a uniform, independent rating and labeling system for the energy performance of fenestration (windows and door) product.
In order for a window company to be Energy Star rated, the NFRC requires the window certified to be physically tested at one of their NFRC qualified independent laboratories. At MGM we use NCTL laboratories. The first step to qualify a window is to send a test specimen (a window) to the test lab. The lab will then install this window into a chamber in which they can physically measure the heat that passes through the window. The setup looks somewhat like an intensive care unit at the hospital. Thermocouples are taped to the glass, sash and mainframe and the temperature is monitored. (About the only thing they don’t monitor is the pulse of the window.) Engineers then calculate the heat that passes through the test specimen. Once this is done, then the basic U-value is determined. This test is typically done with clear glass. Various U-values for different options, such as Low-E glass, grids between the glass, grey glass, etc., are then simulated via a computer algorithm created by the Lawrence Berkeley laboratories. (I know this article is laden with links, but I want to get you as much reference material as you can stand. So here’s another, a link to the NFRC simulation manual. If you download this manual you can read and know exactly how energy loss is approximated through windows and doors. It’s a technical read, but it is very clear and worth the effort if you are employed in the fenestration industry. )
My major in college was Mechanical Engineering and I liked Heat Transfer and Thermodynamics so I created a neat little payback analysis for our windows and doors. (No, I do not have a pocket protector, and, no, I do not wear white tape on my reading glasses.)
I have spent most of this article explaining how the U-value is determined because U-value is the most important factor that the consumer should understand when trying to conserve energy. The most bang for the buck when it comes to U-factor is specifying Low-E glass in your windows and doors. We use Cardinal glass Low-E which is probably the best technology in the industry. Other suppliers of Low-E glass include Guardian Glass and AGC Glass. I have written a few articles on Solar Heat Gain Coefficient (SHGC) and Low-E glass. For more on Visible Transmittance, Air Leakage and Condensation Resistance follow this link to the NFRC website.
After all this is done, the EPA, in conjunction with NFRC, created a table and map with which the user must determine the U-values and the SHGC that must be complied within a particular geographic location. You can find that map by going to the energy star webpage. The Energy Star web page has a new wizard that you can use to find out the U-Factors required in your area. Here’s link…..U-factor climate zone finder.
This map and table is the bible that you have to reference in order to see if the window you want to purchase is Energy Star rated. Let’s assume you live in an area colored in blue. To be Energy Star compliant you will have to have a window with a U-value of 0.30 or less. If you live in an area colored in red, you will have to have a window with a U-value of 0.60 or less. So, if you live in the blue area you will have to have a window with Low-E glass and if you live in the red area you can get by with a window with clear glass. It gets complicated in the transition areas. Look at the map and locate St. Louis, MO. You will not be able to find it with any certainty. So how do, you, the consumer, determine what standard to use? The best solution is to go to your local lumber yard. They will have a good handle on it because they deal with the codes and the codes inspectors on a daily basis. It is typically left up to the codes department in your particular area to interpret the map.
We have a chart completed that conveniently assembles all the information relating to all MGM Industries fenestration products and how it relates to Energy Star ratings. Go to MGM meets Energy Star (make sure you see the forth page which has the Energy Star map.) Sorry for such a long winded article, but that’s the best I can do. If you got here by a search engine, go to MGM’s website to see some of the best energy efficient vinyl windows in the world.