Triple vs Double Pane Windows: What's the Difference?

Double-pane windows, also known as dual-pane windows or double-glazed windows, have two panes of glass, many with insulating argon gas between the panes. The additional layer of glass with an insulating gap in between acts as a sound barrier and improves energy efficiency. At Pella, double-pane glass comes standard on all windows.

Triple-pane windows, also referred to as triple-glazed windows, have three panes of glass. Like double-pane windows, there is a gap between panes which can house an insulating gas. The increased insulating air space of triple-pane glass delivers even better energy efficiency and noise reduction. This glass option is an upgrade available on select Pella windows.

Both dual-pane and triple-pane windows can allow for blinds- and shades-between-the-glass as well as grilles-between-the-glass. Tucked in the gap between glass panes, these window fashions are protected from dust, damage and little hands. Additionally, because they are located between panes of glass, the surface of the window remains smooth, making it easier to clean.

When considering window replacement options, cost seems to be top of mind for many people. As you might expect, triple-pane windows are typically more expensive. The additional cost is a result of extra material and a more complex manufacturing process. According to Essential Home and Garden, dual-pane windows usually pay for themselves a little more quickly. However, triple-pane windows typically pay off if you plan to stay in your home for the long run. Not to mention the increased value and comfort that triple-pane windows offer a home.

When it comes to energy efficiency, both dual- and triple-pane windows are more efficient than single-pane windows. Dual-pane glass insulates almost twice as well as single-pane, while triple-pane glass maximizes energy efficiency. In fact, Pella Lifestyle Series has triple-pane options that are on average 79% more energy efficient than single-pane windows.¹⁷ So what makes double- and triple-pane window glass options more energy efficient?

To begin with, a virtually invisible Low-E coating can be applied to all glass at Pella to help reflect heat and keep your home more comfortable by blocking most of the sun’s harmful ultraviolet rays. While both dual- and triple-pane windows feature Low-E glass, three panes of glass block even more of the sun’s ultraviolet rays, helping keep your home more comfortable and efficient year-round.

Another factor contributing to improved energy efficiency is the insulating value of a window. The rating measurement for the overall insulating value of a window is called the R-value. The higher the R-value, the better insulated the window is. In double- and triple-pane windows, there is space between each pane of glass. Inert argon gas can be used between panes of glass to offer additional layers of insulation and help reduce thermal transfer. Since triple-pane windows have more layers, the insulating R-value is better than that of dual-pane windows.

To measure the sound isolation of a window, we use something called the STC rating. STC stands for sound transmission class. The higher the STC rating, the better sound isolation the window can achieve. While completely soundproof windows don’t exist, both double- and triple-pane glass options offer significant noise reduction in comparison to single-pane glass. As described above, the space and gas between individual panes of glass act as insulators, which also help dampen outside noises. Therefore, as you add panes of glass to a window, the amount of noise that can travel through is reduced. In addition, adding panes with different glass thicknesses helps dampen sounds at different frequencies. Three panes of glass with mixed glass thickness will disrupt the most sound waves to reduce noise transmission and achieve the highest STC rating.

While triple-pane windows cost more than double-pane windows, they offer many added benefits, from improved efficiency to sound reduction. When deciding if triple-pane windows are worth purchasing, consider how long you plan to stay in your home. Will you be staying long enough to recoup the investment with energy savings? Also, think about the climate you live in. Triple-pane windows do a better job at reducing thermal transfer, so these might be the best windows for your region if you frequently experience extreme cold or hot weather. The bottom line is this – the benefits of replacement windows with triple-pane glass may be worth the additional cost if you have the right conditions to recoup your investment over time.