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Window Glass – Performance Comparisons

Window Glass Performance Comparisons

Your upcoming window purchase is important. You need to spend as much money as you can afford on the glass. If you spend wisely, you will get long-term benefits. The charts below illustrate this clearly. Look at the following chart. It is the Winter Performance Chart.

The insulating values of windows are measured in U-values. Low U-values mean BIG energy savings. The Low E glass that contains the invisible heat films simply work the best. If you sit or work near windows during cold winter months, you need windows that have the lowest U-value you can buy. The inner pane of glass in these windows will be warmer to the touch and as such will produce fewer cold convection drafts.

Summer heat gain is also a big concern. The sun's infrared heat streams in through regular dual pane insulated glass. Old technology hard-coat Low E glass doesn't help too much in blocking solar heat gain. Look at the following chart.

It clearly shows that once again windows that contain the invisible heat film do the best at blocking the solar heat gain from entering your home. Invisible heat films are a must if your home contains lots of windows that face west, southwest, south and southeast. Heat gain from these exposures can be massive in the summer months. If you run central air conditioning in your home, windows that contain the invisible heat films will help you lower your cooling costs.

If the window sales people look confused when you mention U-values and Solar Heat Gain Coefficients, go elsewhere! The two charts are courtesy of Gilkey Windows in Cincinnati, Ohio.

Remember, when comparing SHGCs, lower numbers are better. For example, a window with a SHGC of .19 is a better window than one with a rating of .34. Another tip is to be very careful of verbal promises. If a window salesperson promises you something, make sure the exact wording is in the contract. Never accept verbal promises or excuses. Remember, excuses are reasons for failure.

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