Homeowner's Guide to Energy Efficient Windows

Many factors go into making your home more or less energy efficient. The same can be said, maybe surprisingly so, just for windows. Whether it’s keeping cold out in a Michigan winter or keeping the AC in in the middle of a Texas summer, windows help determine a whole home’s efficiency, comfort, safety, looks, and more. 

Knowing how windows can affect your home’s efficiency and your electric bill can help you make smart improvements. If you’re thinking about replacing your windows, energy efficiency should be part of the equation. Here’s what you need to know to make the right decision.

The Benefits of Energy Efficient Windows

Whether your primary goals are energy efficiency and saving money or not, you should consider efficiency as one potential benefit of a window project. According to the U.S. Department of Energy, 25-30% of heat gain or loss in a residence transfers in or out of the windows. 

While direct savings on a monthly electric bill may take years or even decades to offset the cost of the new windows, you may see significant savings, but also with patience, from your HVAC system. More efficient windows put less strain on your home’s heating and cooling. This means fewer repair calls and additional years before an expensive HVAC overhaul.

Other benefits of new windows include safety, overall comfort, appearance, improved home resale value, and, depending on your climate, being better prepared for bad weather. 

What Makes a Window Energy Efficient?

Many factors go into a window’s energy efficiency. For starters, take the number of panes. There are single-, double-, and triple-paned windows, which are exactly as they sound, with one, two or three panes of glass. Triple-paned windows are most efficient, but are more expensive. 

You can fill the space between the panes with insulative gas such as argon or krypton to improve the window’s ability to keep heat in or out. The window frame is also important to insulation and efficiency. Vinyl, composite, and fiberglass are the most common frames for new windows. Fiberglass framing is the most efficient.

Coating is another option. Low-E windows are coated to provide low emissivity, or prevent ultraviolet and infrared light from going through. Along with the health benefits of shielding you from ultraviolet light, it improves energy efficiency, too, by keeping homes cooler.

The absolute top choice for efficiency, with cost as no concern, would be a triple-pane window with fiberglass framing. In most regions and climates of the country, an insulated double-pane window with vinyl framing is a good pairing of efficiency and affordability. 

With or without doing a total replacement, you can decrease the energy loss through your windows by adding caulk or weatherstripping, putting up blinds or curtains, and outdoors, putting up overhangs or awnings, or planting trees.

Check the Label

Like water heaters, dryers, and other appliances, windows come with a label detailing their efficiency metrics. For an in depth explanation of what the numbers mean, you can go to the people who make the ratings, the National Fenestration Rating Council, but we’ll cover the basics below.

In a warmer region, where cooling efficiency is what you need most, look for windows with a low solar heat gain coefficient (SHGC), low E-Coating, and low U-Factor. In cooler regions, where keeping heat in is more important more often, look for a high SHGC and low U-Factor. What do these terms mean? 

• Solar heat gain coefficient (SHGC): Measures how well a window resists unwanted heat gained. The lower the number, a decimal between 0 and 1, such as 0.25, the better the window does keeping heat out of your home while running the AC in the summer.
• U-Factor: A metric of how well a window keeps heat from escaping from inside to outside.The lower the number, from 0.2 to 1.2, the better the window keeps heat inside.
• Visible transmittance (VT): VT measures how much daylight passes through a window. The higher the number, between 0 and 1, the more natural light comes through.
• Air leakage: This number measures how much air enters inside through a window. The lower the number, from 0.1-0.3, the better.

How Much Do Energy Efficient Windows Cost?

The cost of replacing windows, per window, starts at about $150 and goes to $5,000. According to a study from the National Renewable Energy Lab (PDF), the cost of replacing a window in 2019 fell between $600 and $900. The study, which looked at data from real-world projects, showed that cost varied by region and the number of windows installed. The per-window cost might be lower with a larger project. It can be more if you’re talking about bay windows, bow windows, or other large or specialized windows. Consider the size, shape, insulation, frame material, sealing, coating, and labor, and you can see why we’re talking about such a wide range. 

Again, this is per window. If the renovation project is replacing all the windows in your home, take the average per window and multiply it by the number of windows you need to replace.

Will Energy Efficient Windows Pay for Themselves?

The simple answer is, yes, it’s possible, but it will take a while. It’s likely to take a decade or longer. 

Energy Star estimates efficient windows save a household $200-600 a year. Take a relatively moderately-priced replacement job of $5,000 and an optimistic energy bill savings per year and, even then, you’ve got a break even period of about 10 years. There are other factors which can skew the numbers for or against the real savings you’ll see. Going from old single-pane windows to new double- or triple-pane windows will tend to give better energy savings. If you’re replacing relatively efficient windows, for example, insulated double-pane windows with newer insulated double-pane windows, you should see some savings, but likely not at the upper end of the Energy Star estimate.

It may be harder to directly calculate, but if energy efficient windows help reduce demand on your HVAC system and extend its life, upgraded windows could be a sound financial decision. 

Financial Incentives for Energy Efficient Windows

There is a federal tax credit for installing Energy Star-approved windows on a primary residence. A taxpayer can claim 30% of the project, up to $600. You can find filing instructions with the IRS. You can search Energy Star-approved windows here.

Some states and localities have incentives or tax credits. Energy Star has a rebate finder tool where you can enter your zip code to see what’s available. 

When Should I Replace My Windows?

Consider the age of your existing windows and your home. An older home, with older windows, is more likely to have single-pane windows or worn seals, even if the windows don’t seem to be in need of replacement. Then, consider the gas insulation between panes along with the framing. Worn or compromised sealing and insulation will let heat get in or out when you don’t want it to.

One more important consideration is safety. The functionality of windows could be vitally important to you and your family in an emergency.

If making your home more energy efficient is a larger goal for you, going solar could be another idea worth learning about. Palmetto’s experts are happy to help. Check out our solar savings calculator or reach out with our contact form.

FAQs

Are energy efficient windows worth the cost?

As far as savings on your energy bills directly adding up to the cost of new windows, the answer can be yes, but a very long-term yes. You’re more likely to see new energy efficient windows be worth it in helping to keep your home HVAC system running better and longer.

What are the best insulated windows for cold weather?

In short, triple-pane windows, with two layers of gas insulation, are the most efficient home windows in colder climates. 

Can I get a tax credit for energy efficient windows?

Yes. There is a $600 federal tax credit. There are some states and localities with additional tax credits or incentives.

What can I do to make my current windows more energy efficient?

You can do a few easy things, inside and out, to make your current windows more efficient. Check your windows for leaks or cracks. Add weatherstripping or caulk to seal any gaps or holes. You can put up blinds or curtains, which can add an additional insulating layer between your home and the outdoors. Outside, you can plant trees or put up awnings or shutters to provide shade and keep your home a bit cooler.
How are energy efficient windows more sustainable?

Energy efficient windows can reduce your energy consumption and carbon footprint by keeping your home a more constant temperature while running your HVAC system less. There’s also a positive environmental impact from related benefits such as replacing an HVAC system less often.