Also called "double pane" windows, thermally insulated glass windows contain two panes of glass. When the windows are manufactured, the space between the panes are filled with air or gas. The glass is then hermetically sealed along their perimeters. The filled space adds insulation to the window. Thermally insulated glass windows are much warmer to the touch compared with single-pane windows. They help keep heat and cool air in, therefore reducing energy bills.
Eventually, all thermally insulated windows fail. The seals will leak and allow the air or gas to escape from between the panes. The leaks will also allow moisture to enter. Thermally insulated windows have to withstand the harsh elements. If a window doesn't have proper drainage, rain water can ruin the seals. Excessive heat from direct sunlight causes the glass to expand and contract. This action can weaken the window seals. In time, the seals are bound to wear out.
When the seal on this type of window leaks, you'll see condensation in between the two panes. Unfortunately, you cannot fix the seals. The only fix is for the glass to be replaced. This requires a professional service. The first step is to check the manufacturer's warranty. Replacing the thermally insulated glass might not cost you a dime. Whether the warranty covers the window or not, it's a good idea to check with the manufacturer about replacement options.
Even though all thermally insulated window seals will fail eventually, there are a few things you can do to help them last longer. Inspect the windows on a regular basis. Check the sash frames to ensure they aren't damaged or faulty. (Faulty frames can come apart, for example.) Check the seals on the windows. too. Contact the manufacturer if the frames need repair, or if the seals are compromised. Don't use products on the thermally insulated windows that can damage the seal. These include harsh window cleaners, sealants and paints.