How to Gauge Efficiency
The following industry standard benchmarks will help you to compare windows.
U-Value. A unit of measure that records the overall heat transfer of a window, lower values provide better insulation. Look for a value of 0.33 or less.
Visual Transmission (VT). Windows with a high VT are easy to see through and admit lots of natural light, reducing your need for artificial light. Some tints and coatings can reduce visible light and will have lower VT ratings. For most people, VT ratings above 60% look clear. VT ratings at or below 50% begin to look dark or reflective.
Solar Heat Gain Coefficient (SHGC). SHGC calculates the available amount of solar heat that passes through a window. It uses a scale of 0, for none, to 1 for 100% available sunlight. In cold climates, consider windows with a SHGC of 0.40 to 0.55. In warm climates, windows should have a SHGC rating of less than 0.40.
Air Leakage. Properly constructed and installed windows should allow very little air to pass through them—when closed of course. Air leakage is measured in cubic feet per minute per square foot of surface area. Only consider windows with a value of less than 0.30 cfm/ft2.
New windows are a great way to lower your heating and cooling bills by improving the energy efficiency of your home. You can choose from a variety of glass options that hold up to Minnesota weather, including insulating glass and double- and triple-paned windows. Talk to your Minnesota window contractor to help you with your new or replacement window decisions.
Tags: Air Leakage, Solar Heat Gain Coefficient, U-value, Visual Transmission
