This article is the fourth in a series of 15 articles where we “decode” some of the industry terms surrounding replacement windows. Stay tuned for upcoming posts that we hope will help educate San Diego homeowners and allow them to make more informed decisions.
If you’ve started researching replacement windows for your San Diego home, you may have come across the term “glazing system”. This term refers to a combination of elements that contribute to the overall energy efficiency of a window. A good glazing system reduces heat transfer and air leakage through your windows, making your home more comfortable and requiring you to use your air conditioner or heater less often.
Virtually every manufacturer of replacement windows has its own glazing system, and they typically have a trademarked name like QuadraTherm, ProSolar, AdvancedComfort, or Energy Saver Plus, to name a few. It can be confusing for San Diego homeowners looking for energy efficient replacement windows, because it seems like you’ll never be able to compare “apples to apples”. Fortunately, there are common elements in window glazing systems that you can analyze. Here are a few of the important ones to consider:
Double or Triple Panes
Most of the replacement windows you’ll find on the market today are double pane windows, meaning they have two panes of glass. Almost any double pane window will be an improvement when it comes to energy efficiency over older, single pane windows. Some replacement window companies in San Diego even sell triple pane windows (with three panes of glass). However, most replacement window experts will agree that the slightly increased energy efficiency in triple pane windows over double pane windows does not justify the increase in price, which can be quite substantial.
Many people who hear the words “window coatings” visualize the old tinted window films that were often applied to windows to reduce glare and help keep the inside of the home cool. Today’s window coatings are much more sophisticated. They are typically made of metal oxides and are so thin and so clear that you wouldn’t even know they were there! They are often called low-emissivity or low-e coatings, and they greatly reduce the amount of heat transfer from the outside to the inside of your home. You can get windows with coatings only on the exterior glass to work against solar heat gain, and you can also find windows that have an inside coating that keeps the warm air in, when it’s cold outside.
Look for windows with coatings that still allow in a good amount of natural light by comparing their visible transmittance (VLT) numbers. Clear glass, with no coatings, will typically have a VT number around .80 or .90, while a window with a good energy efficient coating will have a VT number around .60. A higher VT number means more natural light is allowed to enter the home.
Insulating Gas Fills
In double and triple pane windows, what’s in between the panes is very important. High quality windows will have an inert gas, such as argon or krypton, injected in between the panes to help reduce heat transfer. For some replacement window manufacturers this is an upgrade, while others include it standard in their glazing systems.
The type of spacer used to separate the panes of glass is another important aspect of a glazing system. In lesser quality windows, a metal spacer—typically made of aluminum—will often be used. A better option is a spacer made with foam, which offers the best in thermal efficiency. As a bonus, foam spacers also help with sound absorption and help to reduce window condensation!
So, there you have it—the basics of glazing systems! You can do some research online to start comparing the glazing systems of the replacement windows you’re interested in, or talk to your local San Diego replacement window dealer to get any of your questions answered.