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Guide to Energy-Efficient Windows

July 28th, 2021, 12:09 PM

Energy-efficient windows help you keep your home comfortable and reduce your utility bills year-round — sounds great, right? But with so many different products on the market, how do you know if the windows you're getting are truly energy efficient? 

In this guide, we'll help you understand the different factors that make windows most energy-efficient and tell you what to look for when you're shopping for your new windows.

How is energy efficiency measured? 

In the United States, window energy efficiency ratings are given by the National Fenestration Rating Council (NFRC). The term "fenestration" refers to all things related to windows, doors, and skylights. This term comes from the Latin word for fenestra, which means "opening."

The NFRC label can help you easily compare energy-efficient windows by providing you with universal performance ratings in multiple categories.

The NFRC categories for windows are:

  • U-Factor (how well the windows prevent heat from escaping)
  • Solar Heat Gain Coefficient (how well the windows keep the sun's heat out)
  • Visible Transmittance (how well the windows let natural light in)
  • Air Leakage (how well the windows block drafts)

For all the above ratings except visible transmittance, the lower the number, the better. A higher visible transmittance rating means the windows let more light in.

When you're looking for the best energy-efficient windows, the easiest way to make sure you're getting a good product is to look for the ENERGY STAR label. 

ENERGY STAR is an initiative of the Environmental Protection Agency (EPA) meant to identify products that meet U.S. government standards for energy efficiency.

Whereas the NFRC's standards break down energy efficiency with ratings, an ENERGY STAR certification simply means that the product is proven to be energy efficient and environmentally friendly.

In order for windows to gain an ENERGY STAR classification, they must be manufactured by a certified ENERGY STAR partner and pass the NFRC's testing, certification, and verification process and receive ratings that meet the EPA's guidelines.

When you purchase ENERGY STAR windows, you can be sure you're getting a product that will keep your home cool in the summer and warm during the winter, as well as contribute to saving the environment.

What makes windows energy efficient?

So, now that you know how to identify energy-efficient windows, let's take a closer look at what actually makes windows more environmentally friendly.

Major factors that contribute to window energy efficiency:

  • Framing materials
  • Sealing/weatherstripping
  • Double- or triple-pane insulation
  • Low-e (low-emissivity) coatings
  • Gas fills

High-quality, low-maintenance framing materials make windows more energy efficient by reducing heat transfer and increasing insulation. 

The best window frames are made of fiberglass, vinyl, aluminum, wood, composites, or a combination of the aforementioned materials.

No matter how good the framing is, a window can only be energy efficient if it also has good sealing and weatherstripping to ensure a tight fit.

This type of sealing is made of either rubber or metal and is designed to keep out drafts and prevent heat from escaping through tiny cracks around the window.

Also heavily influencing the energy efficiency of a window is how many panes of glass it has. Single-pane glass windows, or windows with only one sheet of glass, are not energy efficient. 

For a window to be most energy-efficient, double- or triple-paned models are best. The space between the panes is often filled with a layer of nonreactive insulating gas (such as argon or krypton) to better regulate temperature between the inside and outside.

In addition to multiple panes of glass, windows can also have special low-e, or low-emissivity, coatings. These are invisible metallic coatings that go right on top of the regular glass to further improve its performance.

Can older windows be upgraded to be more energy efficient?

If your home has old windows, the best way to improve its energy efficiency is to replace them with ENERGY STAR windows. However, we know this isn't always in the budget.

Fortunately, there are other ways to upgrade your windows to make them more energy-efficient without replacing them altogether. 

For starters, you can always upgrade the weatherstripping to properly seal your windows. This is probably the most common area that older windows fail to perform in. 

When you seal up all the invisible gaps around your windows, you can drastically reduce air leakage and improve insulation. 

There are a few different ways you can find gaps around windows. For instance, you can try shining a flashlight around the windows at night and look at where light comes through. 

Another test you can do is to light a stick of incense and hold it near the window, looking at where the smoke flows through.

Besides improving the sealings, you can also replace the window frames with energy-efficient framing to improve the performance of your windows without replacing the glass itself. 

Or, you can add a layer of glass over the existing panes to essentially turn your windows into double-pane windows. Note that this requires very careful measurement and precision, so it should always be done by a professional.

The final option you have is to apply low-e window film to all your windows. These special coatings go right on top of the existing glass and are virtually invisible.

It's important to have the low-e window film installed by a window film specialist to ensure proper performance. When applied incorrectly, low-e window film can actually cause windows to break.

Energy-efficient replacement windows from Hodges

If your utility bills are high, Hodges has the best energy-efficient replacement windows for you from all the industry's leading manufacturers. 

All of our suppliers are ENERGY STAR partners, so you can be sure that you're getting the real deal. We're especially proud to offer windows from ProVia, the 2020 ENERGY STAR partner of the year.

Contact us today for more information about how we can help you make your home more energy-efficient and cut down on your monthly heating and cooling costs.


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