Whether you’re trying to reduce your impact on the environment or just want to cut down on your utility bills, energy-efficient windows are most likely going to be something you’ll be considering when you make your next window purchase.

As indicated by their name, energy-efficient windows are characterized by their ability to prevent heat from passing through them, specifically the heat from outside during the summer and the heat from inside during the winter. Proper energy-efficient windows are typically Energy Star® certified through either having their manufacturer as an Energy Star® Partner or the individual window model passing certain tests that allow it to earn that title.

Energy Star is a government-backed organization that certifies products for being energy efficient, and they are the industry’s standard when it comes to energy efficiency certifications. Although there aren’t specific types of technology that are required to earn that certification, there are certain technologies that are frequently used in Energy Star® certified windows that make them more likely to earn that title. To get a better idea of exactly what an energy-efficient window is, you’ll need to know what those features and technologies are. We’ll expand on them down below.

Double-/Triple-Paned, Gas-Filled Glass:

Glass is what makes up the majority of any window, and to make a window energy-efficient, it only follows that the glass must do a good job at preventing heat from passing through. One of the best and cheapest options that enable the glass portion of the window to do that is to double or triple up the glass panels and fill the space between them with a gas that’s denser than regular air. The gas used is typically argon or krypton, which are dense, inert gases that are completely harmless.

Some people might even opt for using xenon as the gas filler, which is denser than argon and krypton and does a better job at insulating, but with a heftier price tag. For more information on gas-filled windows, check out this article (attach a hyperlink to highlighted text).

Low-E Glass:

Low-E glass is another type of technology that goes into making a window energy efficient by preventing heat from passing through. Low-E glass gets that feature from the microscopically-thin, transparent metal layer that is coated on to it before installation.

Low-E glass is usually coupled up with gas-filled windows to protect the metal coating from corrosion, which makes this option even more energy efficient. Low-E glass prevents heat from passing through by blocking the passage of infrared radiation, which is the spectrum in which most heat is emitted in. For more information on Low-E Glass, check out this article.

Quality Frame Materials:

The frame makes up the rest of the window after the glass, and it also follows that it should be made out of materials that do a good job at insulating. One of the materials that does that job the best is fiberglass, and it is characterized by its extreme durability and low-maintenance performance. To increase a window’s insulating properties, some manufacturers fill the hollow parts of the fiberglass with insulating foam which doesn’t add much to the window’s cost.

Another frame material that provides excellent heat insulation is vinyl, despite some of its drawbacks such as it’s susceptibility to warping when exposed to high temperatures. Wood and composite (a combination of wood byproducts and plastic) come right after fiberglass and vinyl in terms of insulation.

One material you should avoid is aluminum because of how conductive it is, which is typical for any metal. If using metal as the frame’s material is a must, then hybrid windows are a good choice as they combine the strength and durability of metal with the insulating properties of wood through having the exterior portion of the frame as aluminum and the interior as wood.


Insulating Edge Spacers:

If you’re going to opt for double- or triple-paned windows, then using insulating spacers are a must. Spacers are what hold the glass panels in multiple-pane windows apart. Many windows come with an aluminum spacer as default, which can easily conduct heat and decrease the window’s insulating properties. Insulating spacers use materials such as butyl rubber and insulating foam as their primary insulating agents, which are characterized by their excellent insulating properties.


Good Fit/Finish:

How good the fit and finish of the window is one of those things that will either make or break its energy efficiency, and there are no in-betweens at all. The window is either going to be a solid, well-built one that will prevent air, dust, and heat/cold from leaking in and give you an energy-efficient window, or will be the exact opposite.

Even if you were to use the most premium materials but the manufacturer didn’t assemble them properly or miscalculated the angle of the joint, the window would still perform nearly as bad as one without the expensive, premium materials. Even the slightest gaps will let in cold air during the winter and hot air during the summer and will offset any of the insulation the premium materials provide the window with.

That isn’t the mention the many other things that can happen when windows have gaps, such as opening a door for insects and dust to enter or causing the window to degrade and loosen up more rapidly. This is why the workmanship of the manufacturer and the installer is integral to the insulation of your windows; in the end, they’re one of the biggest factors that go into the insulation capabilities of any window.