Well, here we are once again heading for a new version of Energy Star that will begin in 2023 with even tougher requirements. As I completed my travels during the first half of this year, I noticed an overall lack of concern regarding the upcoming Energy Star changes. My customers seemed focused on the present – finding all the components needed to build their windows! However, with business appearing to slow just a bit as we enter the second half of the year, window fabricators are now focusing more on what must be done to meet the new numbers. The requirement that seems to be responsible for most of the concerns is the 0.22 U-Factor for the Northern Zone.

Window fabricators have various options to consider when it comes to reducing U-Factor. But it begins with the frame. The frame design is so important because it dictates not only the frame’s thermal properties but also the limitations on what size of IG unit can be installed within the frame. This is referred to as the glazing capacity. Many of the older frame designs are limited to ¾-1-inch thick IG units, which allows for the use of double pane IG units, but limits the fabricator in terms of squeezing a triple pane IG into the glazing pocket, especially if grids are involved. So many fabricators are shopping for more modern frame designs featuring wider glazing capacities made with multiple air cavities or frames made with foamed or composite materials with lower K- values. The K-Value is a measure of the thermal conductivity of the material or component itself and plays a huge role in determining the overall U-Value of the window. These new frame designs offer larger glazing capacity accommodating IG units up to 1 & 1/8 inches thick. This allows the use of the most energy-efficient triple pane units, which will boost energy performance, thereby helping the fabricator to qualify the window to meet Energy Star 7.0 in the Northern Zone, where the prescriptive value will be set at 0.22 for U-Value. This will be a very difficult number to meet. One scientist involved with NFRC told me that he believes that less than 20% of window frame designs currently being fabricated will be able to meet this 0.22 U-Value requirement without the use of a triple pane IG unit!

After the frame is taken into account, the next factors to come into play involve the actual makeup of the IG unit, including what type of low-E glass is used, the choice of insulating glass spacer and the type of gas that is chosen to occupy the cavities within the IGU. Triple- stack low-E and 4th Surface low-E coatings will be called into play when optimizing the center of glass U-Value. This is because the glass portion of a window takes up most of the total square footage of the window itself and is of critical importance when lowering U-Value. Krypton gas shines in smaller confined areas, and it can make a significant impact when used in a triple pane insulating glass unit. The problem with krypton, however, is that it has skyrocketed in cost in the last few years. The last time I checked, krypton was selling at more than $5 per liter, which puts the total price of a tank at $50K. Many fabricators I know have a hard time passing this cost along, so they are choosing to stick with argon until krypton prices come back to the realm of practicality. I have put together a krypton cost calculator for my customers who want to see what overall cost it adds to their window of given dimensions and airspace so that they can decide if krypton still has a place in their product catalog.

Finally, warm-edge spacer systems will be employed in most residential applications. Window fabricators with aging production lines will look at the overall prospect of investing in new IG lines that offer automation while using warm-edge spacers with the best or lowest K-Value. Indeed, in many cases, the K-Value of the spacer system can be the difference in meeting a certain U-Value after thermal simulation and rounding procedures are considered. At the same time, a new production line can help make up the differences of using higher-cost components by minimizing labor costs while improving product consistency. Remember, robots only need to be taught once and do not call in sick or walk off the job!

The end of the year will be here before you know it. The task of figuring out which options will get you to where you choose to be in terms of performance vs. cost can be daunting. With each option comes potentially higher component costs. But opportunities to automate production methods have never been better in the fenestration industry. Automation can be the key to providing your customers with the highest performing products while minimizing labor costs and improving quality. So, it’s time to get your game plan together now. Get ready, get set, and go!


  1. Interesting read Mr. Plavecsky. What is your opinion pertaining to the level of confidence of available hardware systems being fully capable of actuating the heavier sash that come with a .22 U value triple glazed IGU? Also, have do the fill retention characteristics of Krypton and argon gas compare?

  2. Interesting article but surprised not to have any mention of thin triple pane IGUs that fit into existing double pane glazing pockets. I recently was in a manufacturing plant and saw large quantities of thin glass being used and processed on glass tables without any breakage problems. Several companies are already selling thin triples. I also wonder which company will be the first to bring thin triples with only one spacer to market at volume. The future can combine all of the advanced framing improvements with the best glass improvements to get us below the 0.20 Most Efficient criteria.

  3. Brian
    Most of the major hardware suppliers have heavy duty hardware that will handle the weight of the heavier triple pane units. The problem here is that this will further drive up the cost of the overall window system. “Skinny triple pane” units are being developed which will minimize the extra weight required. Look for a future blog on this topic. Krypton gas retention is not an issue as long as the correct IG sealants are employed. Workmanship is also critical here as tiny flaws in the sealant to glass interface can lead to gas loss and subsequent loss of thermal performance.

  4. Marc
    Excellent point! Yes…skinny triples are entering the market and there are some exciting new developments in this area just around the corner. Stay tuned for an upcoming blog on this topic!

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