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Do Blinds between the Glass improve energy efficiency? Alex

Good question, Alex! You know, it would seem that a window with a blind or a shade permanently sealed inside a window or door would offer greater energy efficiency. There are some companies out there that claim this is true.

However, the key to understanding energy efficiency in windows is based on understanding window science. And really, that’s not hard, because it’s all about the glass—low-e glass and argon gas fill, to be exact!

Everyone who reads my blog probably knows by now what I mean by these two terms: Low-e glass, just to recap, is glass that has been coated with a very thin metallic (usually silver oxide) layer that deflects radiant heat away from your windows. And when argon gas is filled between the two panes of glass, it slows down the transfer of heat even more.

That’s the energy efficiency package – and it resides in the glass unit and in the construction of the window itself. Now, you go putting something inside that “glass sandwich” and you are effectively “compromising” your window’s energy efficiency, even if it is a pretty “mini blind”.

And here’s why. Some of these windows and doors are manufactured with two panes of glass and the blind is set inside, reducing the practicality for argon fill and simply eliminating the use of a low-e coating because silver oxide is easily scratched. (So you can see why the low-e would not be used in this construction.) No energy efficiency features here, just a blind.

To be fair, there is also a triple pane design available these days that is constructed so that the blinds sit in their own glass “sandwich” and a separate third pane, with low-e coating, is placed on top. Some argon gas is filled between the space, but that space, is now much smaller…

And then there is a popular snap-in design that cannot possibly contain argon gas, because every time you open it to clean or service the blind inside, the argon would vanish into thin air! And of course the low-e coating is not there either.

So bottom line—blinds inside the glass do affect the energy package on windows and sliding doors. A blind inside the glass can only eliminate heat the same way any curtain will—by blocking the transmission of light into the home. Sure some “heat” gets blocked when you draw your curtains, but low-e glass is absolutely essential for energy efficiency—it’s the only way to reflect radiant heat back to its source.

So if you really like the idea of blinds between the glass, just remember when you’re out shopping for them to ask the company or the manufacturer how they’re constructed—with a single insulated glass unit or with a third low-e coated pane? For more info before you shop, check out my article on blinds between the glass.

Gerry Rogers About Gerry Rogers

Gerry Rogers is the President of Mr. Rogers Windows

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