With Energy Star 7 looming on the horizon, I am seeing fabricators considering one of three main paths.

The Wayward Sons

With requirements becoming more difficult and costly to meet, some fabricators are simply not going to do it any longer, but they will “carry on” (like the song by rock group Kansas) with an alternative course of direction. They are just going to promote other features and benefits that their products and company bring to the table and focus on promoting those instead.

The Conformers

Some will meet the new ES7 requirements but want to take the path of least resistance. They do not want to invest in new tooling to switch frame designs and do not want to upgrade their insulating glass (IG) production to efficiently produce triple-pane IG. Instead, they will squeak by the new northern zone requirements using existing frame designs and by focusing upon the inside lite of glass. By using a fourth-surface low-E coating on the inside lite of glass, it is possible to meet the toughest northern zone requirements either prescriptively or by hitting the equivalent values that are allowed with higher solar heat gain coefficients (SHGC). A fourth-surface low-E coating can make it possible to meet ES7 without using triple-pane IG or upgrading one’s frame design.

The Achievers

Other manufacturers will “pull out all of the stops,” no matter what the cost, and do whatever it takes to market the most energy efficient doors and windows possible. These “Achievers” will be using modern frame designs with wider glazing pockets to accommodate triple-pane units with optimal air gaps, Argon or Krypton gas, low-E on conventional surfaces, and internal cavities or foam designed to minimize heat transfer through the frame itself.

Personally, if I were manufacturing windows, I would choose to be either a Wayward Son or an Achiever instead of taking the middle road.

If I chose to be a Wayward Son, I could still use a National Fenestration Rating Council (NFRC) label, but I would use it to promote condensation resistance in addition to listing a fairly decent U-value, even if my window did not qualify to sport the Energy Star label. Staying with a double-pane unit and using Argon and foam spacer, my double pane window would have significantly better condensation resistance than a double pane unit using a fourth-surface low-E coating.

Here is why: When it is cold outside, heat migrates from inside of a window to the outside, and the inside lite of glass becomes cooler than room temperature. Now take this situation and add in a fourth-surface low-E coating. When a fourth-surface low-E coating is employed, radiant heat from inside the room is immediately reflected right back into the room before it even has a chance to warm that inside lite of glass. Therefore, what you get is a window with a very low U-value, usually in the neighborhood of 0.20 (with a soft-coat low-E also employed on surface number two), but with an unusually low surface temperature on the inside lite of glass. Add in the heat transfer to the outside being caused by very cold wintertime temperatures and you have a recipe for a higher degree of condensation to occur on the inside lite of glass. In some cases, this inside glass temperature can fall below 32F, and this means ice formation.

I will never forget the time I was in a Michigan dealer’s showroom when a call came in with a homeowner complaining about ice, and the salesman did not even know what to say other than, “Are you sure ma’am that it is really ice?” So, as a Wayward Son, I would promote either the Condensation Resistance Factor (CRF) touted by AAMA, or the CR/CI (Condensation Rating or Condensation Index), which is an optional part of NFRC’s labelling program. I would also promote the list of everything else that my window has to offer, other than U-value, such as aesthetics (colors), hardware (security), vision area (connecting to nature), long term durability (warranty), value (features available for the price point), and customer service (ultimate satisfaction).

If I chose to be an Achiever, I would promote the fact that my windows meet the new Energy Star requirements with triple-pane IG configurations that also support the highest degree of condensation resistance on the market. I would also test sound attenuation and add that to my list of features and benefits. As an Achiever, I would promote my company’s investment in new technology that enables my products to truly be state of the art. My pricing is no doubt higher than the Wayward Sons and the Conformers, but it is reflective of the highest level of performance and quality available in the industry. I would also promote the list of everything else mentioned previously, since selling a window is much more than just what is on the NFRC label.

I was discussing all of this with an industry associate and NFRC member today and I thought he summed it up quite nicely. He said: “At the end of the day, it doesn’t matter what science says, it matters what you can sell!”


  1. Placing a lite with Low E coating on surface #4 indicates the coating is not encased in the IG but exposed to interior elements ie. fingers, cleaning solution , dust ect. Doesn’t that have the potential for the Low e coating to be compromised or scratched? Or am I mis understanding the orientation of the Low e coating.

  2. Hi Brian. No you are not misunderstanding. The concerns you raise are valid. The glass fabricators who are making these 4th surface coatings are making them as durable as possible, but you are correct as the coatings are indeed exposed to the indoor environment of the home.

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