3 Key Metrics for Assessing Whole Window Performance

Replacement windows and doors have come such a long way that it’s quite hard to imagine them without their energy-efficient upgrades. In fact, measuring the whole window performance today is all about how much energy savings a window can provide your property after installation. Planning to replace your windows? Let Prestige Windows & Doors, the local leader among window companies, discuss some of the metrics involved in assessing whole window performance for you to know what to look for:

3 Key Metrics for Assessing Whole Window Performance


In simplest terms, U-factor is used to express the insulation value of windows. It measures the rate of heat loss of a window assembly. So, the lower the U-factor, the greater a window’s resistance to heat flow and the better its insulating properties. Most double-pane windows today can have a U-factor of 0.30 or lower. If you live in a region with warmer climates, a low U-Factor is an excellent factor to consider when choosing replacement windows.

Solar Heat Gain Coefficient (SHGC)

This metric is measured as the fraction of incident solar radiation that is admitted through a window, both directly transmitted and absorbed and subsequently released inward. The Solar Heat Gain Coefficient is expressed as a number between 0 and 1, with a lower value indicating that less solar heat is transmitted. This applies to both residential and commercial storefront windows, and is a great way to streamline your options since solar heat gain can provide free heat during the colder months but can also lead to overheating in the summer.

Air Leakage (AL)

Cracks in the window assembly are the leading cause of heat loss and gain. That’s what AL is all about. It is expressed as the equivalent cubic feet of air passing through a square foot of window area. A lower AL means there is less air likely to pass through cracks in the window assembly. An AL rating of 0.30 or less is required for ENERGY STAR certification.

Prestige Windows & Doors is the company to call for commercial storefront doors and windows, as well as residential options. Get in touch with us today by calling (305) 250-2848 or by filling out our contact form.