If you’ve done any research about upgrading your windows, you’ve likely come across data supporting what you already suspected: replacing old windows is a smart move that will save you money. After all, 40% of the average family’s annual energy budget goes toward heating and cooling costs, and replacing the windows in your home is a great way to keep your inside climate airtight and reduce your utility bills.
Switching out your leaky, single-pane, decades-old windows for new models is guaranteed to improve your energy efficiency. But if modern double-pane windows are a smart move, are triple-pane windows even better than double-pane?
In this article, we’ll cover exactly what the difference is between double- and triple-pane windows, and help you determine the best type of windows to fit your particular needs.
What are double-pane and triple-pane windows?
When mass-production of clear, flat glass became feasible in the 20th century, it was an enormous step forward from millenia of paper-covered frames and prohibitively expensive hand-polished plate glass. And it wasn’t long before architects discovered the benefits of doubling up: double-pane windows — where two panes of glass are set in a frame with a small amount of insulating air between them — were introduced to the market in the 1950s.
Double-pane windows proved popular due to the many advantages over their single-pane counterparts. These windows prevent the view-obscuring condensation that forms when there is a significant temperature difference between inside and outside. They are better at reducing noise pollution inside the home. And most importantly, they are better at insulating a home’s indoor environment from sweltering sunshine in the summer and icy cold in the winter, thus reducing energy costs from A/C and heating.
And so the line of reasoning went: if two panes of glass increase energy efficiency, why not make it three? In the 1990s, researchers at the Lawrence Berkeley Laboratory came up with the technology to make triple-pane windows a reality. And over the last thirty years, the environmental movement’s drive for increased energy efficiency has spurred much of the innovation in triple-pane windows. They are an exciting emerging share of the window market, and a forward-thinking choice for more and more homeowners.
In summary: Double-pane windows have two panes of glass and triple-pane windows have three. They both offer excellent energy efficiency, and will help you keep your home comfortable.
But which one will best suit your needs? Let’s explore the differences between them.
Things to Consider When Picking a Window
Consider your Neighborhood: Noise and Safety
First off, there’s no such thing as a sound-proof window. But if you live on a very loud block, or have neighbors that like to party, you may decide to go with a triple-pane window. It simply makes sense that adding a third pane of glass would reduce sounds from outside that make it tough to focus or sleep, and on average triple-pane glass will cut your outside noise by half as compared to single-pane.
The industry uses a rating system called STC (Sound Transmission Class) to measure the sound isolation on windows. The higher the STC rating on your window, the better sound isolation you’ll experience. Get that number up high enough, and you won’t have to hear the neighbors’ teenager’s car stereo pulling into the driveway in the middle of the night.
Triple-pane windows can also provide you with extra security. They are made out of some of the strongest glass on the market— utilizing the same technology that you find in automotive windshield glass. Triple-pane windows can withstand up to 30 swings from a baseball bat! Which might also be helpful if you are the front lawn that hosts that once-a-year football game.
Consider the Light
The light that streams through your windows can make your home feel more spacious, and has a profound effect on mood and circadian rhythm. If you have a great backyard, why not maximize the view and bring in as much light as possible?
Both triple- and double-pane windows are available in a variety of sizes, and can help you maximize your natural light. But while you want your home to be sunny, you may also want to limit dangerous sun exposure. Good news: triple-pane windows will block 97% of UV rays from entering, while double-pane windows block 90%. (And don’t worry — that won’t impact the health of your indoor plants.)
It’s up to you how important that percentage difference is to you. Lowering the UV in your home will ensure that your upholstery doesn’t fade over time, nor will your artwork or painted walls bleach out from the sun.
Neither triple-pane glass nor double-pane will have a discernible effect on the quality of visible light passing through. Unless you are very photosensitive, in this category, double- and triple-pane windows are both a winning choice.
Consider your Climate
You may have come to this home window replacement project with energy saving windows. Rest assured, whichever style window you choose, replacing your old windows will have a big impact on your monthly heating and cooling bills. New windows are hands-down more efficient.
When deciding between double- vs. triple-pane windows, the question becomes, just how low do you want that monthly energy bill to go?
Triple-pane windows are the most energy-efficient windows you can buy. With three panes of glass to travel through (not to mention the between-glass insulation options like argon gas), it’s simply more of a challenge for frigid winter air to creep into your house.
But how do double- and triple-pane windows actually compare? A material’s ability to resist heat flow is measured in R-value. That means a window with a higher R-value is better at insulating the interior of your home than one with a lower R-value. On average, double-pane windows have an R-value of 3-3.7, while triple-pane windows have an R-value of anywhere between 5-8.
Depending on other window treatments, the frames you choose, and the type of glass, this means triple-pane windows can be 40%-50% more efficient at blocking outside temperature fluctuations than double-pane windows. In this race, triple-pane windows clearly win.
Consider your Budget
Let’s get down to brass tacks: the initial investment in triple-pane windows will be higher, as they are more complex to manufacture and come with a correspondingly higher cost. On average, triple-pane windows cost anywhere between $300-$2,700 per window, and double-pane windows, on average, cost between $700-$1,000 per window. Of course, that’s all highly dependent on the size, placement, and customization of the windows you’re installing.
And while triple-pane windows give you a considerable efficiency boost, how this will actually affect your energy bills is highly dependent on the climate in which you live.
According to traditional numbers, that extra pane of glass was estimated to save only 2-3% more than the less-expensive double-pane options on energy costs. With a fractional difference like that, it would take homeowners 20-30 years to recoup the costs of upgrading.
However, more recent studies show that modern triple-pane windows saved an average of 12% on heating and 28% on cooling for a 1,500-square-foot building over the course of two ten-week periods during the winter and summer. And with fuel costs skyrocketing and glass technology constantly improving, it may make increasingly more sense to invest in triple-pane windows.
If your home is located in a region of the country with extreme heat or cold, that increased cost starts to make sense. While it will take you longer to offset the additional cost of these windows, if you are planning to stay in your home for a while, you’ll be there to enjoy the day when your wise decision pays off.
Still, double-pane windows remain the most popular windows on the market, and it’s not hard to understand why. They offer excellent energy efficiency all on their own, and are competitively priced. The manufacturing of double-pane windows is more straightforward, which allows the price of these windows to come in lower than triple-pane windows.
For most folks, double-pane windows perfectly suit their needs. You can offset the additional cost of triple-pane windows if you plan on staying in your home long enough and if the weather in your region of the country puts an excessive strain on your heating or cooling needs, but rest assured that double-pane windows are a smart financial choice that will still bring increased energy efficiency.
What are some other options and add-ons?
Nowadays, there are even more ways to insulate between panes of glass. As we touched on above, instead of moisture-free air, double- or triple-pane windows can be filled with argon gas or krypton gas. This type of gas is non-toxic, colorless and odorless. (You may hear people refer to these windows as “gas-fills.”) Because argon is denser than air, it works as a thermal insulator. The argon slows the transfer of heat through the window, and increases the window’s insulating properties.
Both double- and triple-pane windows can also feature low emissivity (or Low-e) coated glass. Low-e glass is treated with a microscopically thin coating that reflects heat without affecting the amount of visible light that passes through. Low-e coating blocks the sun’s harmful ultraviolet rays, and keeps the temperature in your home more comfortable and efficient year-round.
Both of these options may supplement your double-pane windows’ efficiency to the point where you may not need triple-pane. Or perhaps you live in a particularly harsh environment, in which case it makes sense to invest in all the bells and whistles to keep your home comfortable.
Choose the window that works best for you.
When you sit down to do your back-of-the-envelope calculations on this project, you have some questions to ask yourself. Do you want the additional sound proofing and security that comes with triple pane windows? Does the small reduction of UV rays in your home mean a lot to you and your family?
The choice between double- and triple-pane window glass usually boils down to energy efficiency vs. budget. Are triple-pane windows better than double-pane? That depends on your priorities. Those with an eye on the bottom line will appreciate that double-pane windows give them both energy efficiency and lower cost. People who prioritize maximum energy efficiency and plan on staying in their home for a while tend to opt for triple-pane windows. Out of all of the projects you could tackle around your home, window replacement has the highest return on investment. It’s a smart way to invest in your comfort, increase the value of your home, and boost your curb appeal. According to Remodeling Magazine, homeowners who upgrade their windows can expect a 75% return on investment. Year after year, they rate window replacement as one of the top five smartest home improvements investments you can make.