What are Window Panes?

What are Window Panes?

Window panes are sheets of glass that are housed inside of window frames. Older homes tend to have single-pane windows, but energy-efficient double- and even triple-pane windows are more commonplace in newer residential tract and custom homes.

Window panes vary greatly in size and are used primarily to provide natural lighting inside the home and enhance outside views. It’s hard to imagine a home on the beach in Malibu that lacked expansive windows from which to enjoy the setting sun, or a home in Colorado that didn’t have picture windows to capture stunning views of the Rocky Mountains.

Modernize created this comprehensive guide to window panes to help homeowners understand why glass is the most common material used for window panes, window sizes, and some alternative window pane materials. Read on to learn more about window panes.

Pane vs Panel

Window panes differ from window panels. Interior designers use the term window treatments when discussing how to cover windows. Window panels are any type of covering – though typically fabric – that is hung to cover the window pane. Think of window panels like part of a whole. A panel that’s combined with accessories such as a sash, blackout or insulated liner or another panel, forms a window curtain. Window panels tend to be hemmed at the bottom and attach to a curtain rod with grommets, ties or tabs.

Window Panes: History

Window panes are one of your home’s most distinguishable architectural features. That wasn’t always the case, however.

Window panes were first widely used in homes beginning in the 17th century. These early windows consisted of small rectangular or diamond-shaped window panes set in wood or iron frames that formed a grid. Toward the end of the century, window design moved toward the double-hung sash style that’s still quite common today, with the most common size a 6-over-6 sash.

In the 1800s, methods of flattening window glass were invented and refined, which allowed for the creation of larger window panes. These improvements led to the window sizes that are common in homes throughout the U.S.

Why Are Window Panes Made of Glass?

Glass was first made as far back as 5,000 BC by Phoenician merchants. Molded glass was used to illuminate Imperial Roman bathhouses and to prevent drafts beginning in the first century AD. Beginning in the 8th century, Venice grew to be the glass manufacturing center of the world. The first glass factory in the U.S. was built in Jamestown, Virg. in 1608.

By the 1800s, increased demand for window glass led to the invention of hand-operated glass-making machines, and in 1902 inventor Irving W. Colburn invented a sheet-glass drawing machine that finally made it possible to mass produce window panes.

We have briefly covered the history of glass window panes, but that still doesn’t address the question of why window panes are made from glass instead of other materials. While glass like a soda bottle is fragile, glass window panes are actually quite hard and durable. Tempered glass is common for windows because it breaks into tiny granules rather than jagged shards when broken.

Glass is a solid material even when thin – most residential window panes are made from single-strength glass, which is just 3/32 of an inch thick. Larger window panes, however, such as sliding glass doors, are usually made from 1/8-inch thick glass. An alternative material, such as plastic, would have to be much thicker to span large spaces and withstand wind shear loads.

Glass is also an excellent insulator versus other materials, especially when two panes of window glass are sandwiched together with a layer of argon gas in the middle. And of course, glass provides unobstructed views to the outside world while letting pleasing natural light stream into the home. Lastly, glass is cost-effective, easy to clean, and does not wear or break down over time.

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Single, Double and Triple Paned Windows

As noted earlier, window panes are the sheets of glass that are positioned inside the window frame. In this section we will discuss the difference between single, double and triple pane windows, as well as the benefits of the latter two types of windows. 

Single Pane Windows

There’s a good reason why the majority of windows sold and installed in homes today have either double or triple window panes. Single pane windows might not cost as much as the other two, but homeowners likely will pay more over time in higher energy bills since single pane windows aren’t as energy efficient as double or triple pane windows. They are common in older homes, though they are still sold at many big box home improvement retailers and window specialty stores.

Single pane windows are more susceptible to transmitting outside heat and cold into the house through the process of conduction and through solar transmission since glass is transparent. Multipane windows, on the other hand, are typically filled with a layer of gas between the panes that drastically increases the window’s energy efficiency regardless of whether they directly face the sun or are located in shady areas. According to Energy Star, the federal government-backed symbol that denotes energy efficient products, homeowners in colder northern U.S. climates saved 22 percent, or $366 annually, on their utility bills after replacing single pane windows. Homeowners in hot southern regions, meanwhile, saved 31 percent.

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Double Pane Windows

Double pane windows dominate the window industry because they are less costly than triple pane windows but offer the same energy saving benefits.

As the name suggests, double pane windows utilize two panes of glass. The space between the panes is usually filled with either argon or krypton gas, which greatly increases the window’s R-value (thermal resistance insulation value). The gas helps reduce heat transfer across the window – argon’s thermal conductivity is about 67 percent less than air. Argon is less expensive than krypton, which has even better conductivity properties, so it’s used more often. However, sometimes both noble gasses will be mixed as a compromise between cost and increased thermal conductivity.

Xenon and nitrogen are also used to fill the space between double pane windows.

Triple Pane Windows

Triple pane windows enjoy a lofty status at the top end of the window market because they are the most energy efficient windows available.

Triple pane windows have three sheets of window glass housed inside the window frame. The gaps between the window panes are usually filled with krypton or argon gas. In addition to increased thermal resistance, triple pane windows also offer homeowners superior noise reduction.

Triple pane windows cost more than other types of replacement windows, they are a sound investment only if you know you will stay in your home for a decade or more. If not, homeowners should consider buying dual pane windows since they tend to pay for themselves much quicker in the form of reduced energy bills.

Alternatives to Window Glass Panes

Glass is the most common material used for window panes, but there are some alternative materials available for homeowners who want to go a different route. Here are four of the most common window pane alternative materials:

• Acrylic glass. Commonly known as plexiglass, acrylic glass is gaining traction as an alternative to glass due to its low cost and strength. Plexiglass offers about 17 times the impact resistance of glass. Plexiglass is even more transparent than glass, and it doesn’t give off glare or reflections that are common with glass.
• Plexiglass. There are few differences between acrylic glass and plexiglass. Acrylic glass is manufactured from continuously extruded acrylic sheets. Plexiglass, meanwhile, is made from a cell-casting process where acrylic is poured between two sheets of glass, which results in a higher-quality plastic product. 
• Polycarbonate. Developed to meet demanding specifications where glass and plexiglass aren’t sufficient, polycarbonate windows can be up to 250 times stronger than glass window panes – that’s why it’s commonly used to make bulletproof windows. Polycarbonate also doesn’t require as much structural support, resulting in thinner window frames. 
• Plastic. Often chosen for price, plastic windows can be manufactured with double or triple panes. Plastic windows offer good thermal resistance, low maintenance, and a wide range of designs, colors and styles.

Putting it All Together

Even when armed with loads of information about window panes, styles, benefits and other useful information, it can be difficult to choose replacement windows that meet your project budget and performance expectations.Modernize can put you in touch with reliable window installation contractors in your area who can lend invaluable expertise and insight to the decision-making process. These vetted professionals can help guide your decisions and help you choose the right windows and window panes for your renovation project or new home construction.