Just about every manufacturer I talk to these days is scrambling feverishly to analyze the thermal performance ratings of their various window product lines to make sure they have the most cost-effective solution available to be in compliance with the upcoming Energy Star requirements. The approach I most often see is to rank proposed changes in terms of U- value decrease vs. cost and then of course to pick the combination of changes that gets you there at the least possible cost increase. This may work in the short term, but Energy Star requirements are not going to remain stagnant!  I think everybody knows that what the EPA has in mind is continuous improvement, so every three years or so, there will be a new hurdle to address. So what is the smartest long-term approach to make sure that one will remain ahead of the curve? The answer is to look at the frame!

The frame of the window system has the biggest impact upon overall thermal performance in more than one way. First of all, the material selection of the frame itself is key—vinyl vs. wood vs. thermally-broken aluminum vs. composite. Secondly, there is the design of the cavity of the frame. This also affects thermal performance. Are the internal webs designed to accept foam filling? Can non-metal reinforcements be used? And finally, there is the flexibility of the frame design to allow wider glass packs to accommodate triple pane configurations. Triple pane glass packs with various types and combinations of low-E and gas fills can do amazing things but only if your frame is designed to accommodate them! My point is that, short term, a manufacturer may get by with a change in type of low-E, adding gas filling and/or non-metal spacers if he is already close to U-Value requirement, but longer term it is the overall design, adaptability and flexibility of the frame design that will keep a manufacturer at the front of the pack in the long term!

Also, if you want to play in the Energy Star’s Most Efficient arena, get ready to combine flexible frame designs with triple pane configurations employing the unique properties of Krypton gas. Window grade krypton costs an average of a dollar per liter vs. argon at less than two cents a liter. However, Krypton enables you to market your window product in an elite category of thermal performance. Sure, there are those Surface Number 4 Coatings that some manufacturers are using to get U-Value ratings uncharacteristically low for dual panes, but this author does not condone their use because of possible condensation resistance issues. To me it’s like selling someone a CZ but calling it a diamond. Yes, Krypton is the “Real McCoy” but once again, it is designed to be most useful in triple pane configurations so the frame design has to be flexible in order to allow the option of using glass packs with increased overall thickness characteristic of these triple pane designs.

Thermal performance requirements will keep getting tougher. The government is challenging the industry by continuously raising the bar. The companies that will stay ahead of the curve will be those using a long term approach. So if the frame design you have now cannot allow you to remain a market leader in the long run, then it is time to challenge your extrusion supplier to give you a frame design that can … or go shopping!

1 Comment

  1. Hi Jim,

    This is one of the few situations in our industry where I approve of “nailing it”. You did.

Leave a Reply

Your email address will not be published. Required fields are marked *