Differences Between Single, Double and Triple Pane Windows
How many layers do you need?
When it comes to repairing or replacing windows in your home, the most important decision you’re likely to make is how many panes each window should have. Windows can be single pane, double pane (meaning each frame contains two panes of glass) or triple pane (three panes of glass). Whether more panes equal a big enough energy-savings-bang-for-your-buck is a decision only you can make. We’ll lay out the differences so you can make that decision.
Replacement windows come in a variety of materials and types. Frames are available in aluminum, vinyl, wood or wood wrapped in aluminum or vinyl.
- Aluminum is the cheapest option, but it conducts heat and is not as efficient as the other options.
- Vinyl windows are more expensive than aluminum and provide a higher level of efficiency.
- Wood frames clad in another material are most expensive but generally will last longer than vinyl or aluminum. However, they can be susceptible to problems with moisture trapped behind the wrapping material.
The ability to make repairs is another consideration. Historic wood windows can be repaired and maintained with relative ease by repairing or replacing only deteriorated parts, since the technology is basic and has not changed for over 100 years. Because the designs of replacement windows change, it can sometimes be difficult to find replacement parts for damaged windows of some types. The general understanding is that replacement windows will last anywhere from 6 to 15 years, although many last a considerably longer period of time, depending on the quality of the window and proper maintenance.
Before making any window pane decisions, it’s helpful to familiarize yourself with several common window terms:
- NFRC rating label on windows is the result of independent testing and certification performed by the National Fenestration Rating Council, a non-profit organization. It’s not a recommendation – merely an informative rating on a window’s estimated performance.
- U-Factor is the measurement of how much heat comes through a window via thermal conductivity. A lower U-factor on a product is a good indication that it’s a better-insulating window. Conversely, the R-value of a window refers to how well a window resists heat conduction – so a higher R-value is preferable.
- Glazing refers to the glass used in a window. The number of layers of glazing doesn’t alone equal greater efficiency. A window’s total energy performance depends on many factors. But glazing coatings can significantly improve a window’s U-factor and insulating qualities.
- Low-E stands for low emissivity, the window’s ability to reflect heat, rather than absorbing it when coated with a thin layer of reflective material. If your current windows are still viable, but you’d like to add insulation, Low-E films can be purchased and applied to the outer surfaces of your windows. Application to large or complex windows, however, will normally demand the services of a professional, to achieve the best results.
- Argon or Krypton gas fills are pumped between glazing layers to increase insulation and slow heat transfer. At higher altitudes, however, these gases can often leak out due to differences in air pressure. Air is also commonly used as a filler between multiple window panes.
- Spacers separate multiple panes of glass in a window, to improve the window’s insulation, prevent condensation build-up and prevent heat loss.
Single pane windows
Windows on traditional homes are an important aspect of their architectural character. The size and proportion of the openings, the material they’re made from and the often elegant finishing details are all important in maintaining a building’s original character. In the not so distant past, replacement windows often altered some or all of these unique features. Today, however, many options exist to allow you to replace windows without sacrificing the appearance of your home.
When making decisions about windows in historic homes, it’s important to understand what makes a window significant. For example, are they original to the building; do they reflect the original design of the home – as in the period or regional style; do they reflect any examples of exceptional artisanship or design? If the answer to any of these questions is yes, perhaps you should consider staying with your single pane windows.
Many historic homes (100-plus years old) were designed to be naturally energy-efficient, because at the time they were built, there was no central heating or cooling. The placement and orientation of the house and windows, the size of the overhangs, the planting of trees, the thickness of walls, the design of the windows and other aspects were often equally chosen to naturally maximize energy efficiency.
Repairing, rather than replacing, older, traditional wood windows is historically the “greener” option and a far more sustainable building practice. In certain historic areas around the country, retaining and maintaining original windows are requirements of home ownership. Single pane windows that are professionally and correctly re-glazed, sealed and installed can serve an older home for many more decades. Adding storm windows to the outside of the home is another option that can add another layer of protection to an older home.
Double pane windows
The first step to improving the energy efficiency of a window is to add another pane of glass, which improves efficiency by about 50 percent, compared to single pane windows. This additional layer also traps an insulating layer of air or inert gas between the panes. That extra layer of glass insulates much better than a single layer because only half as much heat or cold passes through the window.
These windows have several advantages over standard windows. Along with providing better insulation, they reduce outside noise and are easier to clean. They can also protect furniture, rugs and other household items from sun damage, while opening and closing easily.
Choosing double pane windows with Low-E coating on the glass will repel UV rays while allowing visible light to enter your home. Heat mirror film also provides additional insulation to double pane windows. Thanks to their increased use in new builds and remodeling work, the prices on these windows have dropped significantly, making them an attractive option when balancing cost and efficiency levels.
Triple pane windows
These windows (also called triple glazed windows) offer the highest efficiency – up to 90% more than single pane windows. With three panes of glass and two spacers instead of one, triple pane windows are much heavier than double pane windows, but wood and fiberglass frames are both strong enough to withstand the weight.
When comparing the U-factor between these and double pane windows, there is an approximate improvement of 20 to 30 percent in overall energy ratings.
Note: Although double and triple pane windows offer serious benefits in terms of increased energy efficiency, they are more expensive than traditional, single pane windows. But the increased initial outlay is eventually returned in reduced utility bills and increased property values.
Every homeowner seeks ways of minimizing the costs of heating and cooling their home. So, whether you’re building a new home or planning to repair or replace existing windows, it’s of key importance to know which choices will give you the biggest bang for your buck, without delivering a blow to your bottom line.