If some or all of your home's windows need to be replaced, then you may have begun looking at different replacement window brands and models. One thing you've likely noticed is that they come in a wide range of prices. There are several reasons for this, but one reason is that replacement windows can come with several different types of glass within the frames. It's important to look closely at the glass and understand what you are getting. Here are some terms you'll see used to describe residential glass window replacements and what they mean.
Double-pane windows have two panes of glass. One is set just inside the other with a small air gap between them. These days, this is the bare minimum you want from a replacement window. Double-pane windows are far better insulators than single-pane windows, thanks to that air gap, and will reduce your energy bills significantly in comparison to single-pane windows.
Triple-pane windows have three panes of glass, set one inside of the other, with two total air gaps. These windows are highly efficient and really well insulated. Most homeowners in moderate climates don't really need them, but if you live somewhere really cold and snowy, they can be a real energy saver.
If you see window glass described as "Low-E," that stands for "low-emissivity." Emissivity is the amount of heat that gets transferred through the glass. Low-e windows, therefore, are windows that do not let a lot of heat pass through. They are coated in a reflective substance that causes the heat waves to bounce off the glass rather than pass through it. These windows look just like any other windows; you can't see the coating on the glass. However, they will save you a bundle of energy by keeping the heat in during the winter and out during the summer.
Impact glass is basically the same as storm glass. It is glass that is made to withstand greater-than-average blows and forces. If you live in a storm-prone area or are worried about break-ins, this is a good type of glass to choose from. It comes with a significantly higher price tag than other replacement window glass, but that's often worth it if the glass doesn't break.
Now you should have a better idea of what all the words and descriptions mean when shopping for replacement windows. Good luck, and enjoy the process.