The Weight of Triple Pane (Triple Glazed) Windows
Since triple pane glass has, by definition, three panes, it typically has 50% more glass than the comparable double pane version. Therefore, the glass is 50% heavier in a triple pane window vs. the same double pane window version.
This can sometimes be a problem. Not all vinyl windows are designed the same. In fact, most vinyl windows are designed to be carry the weight of double pane glass. Specifically, the balance system (which supports the weight of the sashes in a double hung window) is normally designed to support ("balance") the weight of a double pane sash. The balances in a normal vinyl window designed to support double pane glass are typically 1/2" or 3/8" in width.
Problems can occur if the window manufacturer puts triple pane glass in a window designed to only support the weight of double pane. In fact, many window companies refuse to use triple pane, because they don't have a window meant to support it. Unfortunately, some windows companies offer triple pane, but they don't put it in the right window. If triple pane glass is put in a window designed only for double pane, the sashes may feel heavy, and over time the balances may not be able to support the weight, and may fail.
Putting Triple Pane Glass in the Right Window
OK, so we know that triple pane glass isn't right for every window. So what are things to look for in a window to know that triple pane glass is the right fit?
First, you need to know that the window was designed to support the weight of triple pane glass. So the first place to look is the balance system. As mentioned before, most vinyl windows have 1/4" or 3/8" balance systems. If you're considering triple pane glass, this should be a red flag. These balance systems are designed for double pane glass, not triple pane!
Look for a 3/4" or larger balance system if you are considering triple pane windows for your home. This is a sign the the window was designed from the ground up to support the weight of triple pane glass. This is not something that can be faked, either--you can't change out a 1/2" balance system and replace it with a 3/4" balance in the same window frame. There just isn't room in the jambs (sides of the window) if the window wasn't designed for the larger balance.
There are other factors to consider as well. Look for a strong design pressure (DP) rating. This is a rating of the strength of the window frame. Stronger frames can support more weight, without distorting.
Some Final Words About Triple Pane
Triple pane glass is should normally make a more energy efficient window, when compared to double pane. But make sure to consider the following:
- Look for DUAL low-e coatings. Not all triple pane glass is created the same. Look for dual low-e coatings, typically on the inside of the inner and outer panes. If you're not getting two low-e coatings, you're not getting the full benefit of triple pane.
- Look for argon (or even krypton) gas. Three glass panes creates two different pockets of air. Make sure you're getting an insulating air in those pockets.
- Look for the proper balance system. As discussed above. It's crucial!
- Look out for a large price gap between double and triple pane. There shouldn't be a huge price difference between the two options. In fact, some window companies even offer a free upgrade to triple pane glass. But if you're quoted an outrageous increase to get triple pane (30% or higher increase), then chances are the window company doesn't really want to sell triple pane--meaning they know they don't have the right window for it!
As always, make sure to do you're homework, and take you're time when shopping for windows. When done right, triple pane glass is your better option. Just make sure you get all the information, because not all triple pane windows are built the same!
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