Understanding Window Performance Standards

The NFRC or National Fenestration Council uses U-Values and SHGC (Solar Heat Gain Coefficient) to describe the performance of various replacement windows. While these measurements are enough to give you a pretty good idea about how energy-efficient these products are, these are not the only standards you can use to make a decision.

Understanding Window Performance Standards

Let our experts at All American Roofing explain a few more window performance standards that could prove useful when you’re shopping around for new or replacement windows.

Visible Transmittance

SHGC determines how much a room can heat up as sunlight penetrates a window. Visible transmittance, or VT, on the other hand, is related to SHGC but different in a few points. VT measures just how much light the windows allow to pass through itself. Higher VT numbers mean your windows are great at maximizing daylight.

Air Leakage

Your overall efficiency is dependent on how airtight your home’s thermal envelope is. This includes every part of your home from your roofing material, to your siding and insulation, and even your windows and doors. As your HVAC system regulates your indoor temperature, some air might be escaping through very small cracks and other points of leakage in your window assembly. You always want an AL or air leakage value of 0.30 or below to allow for optimum energy efficiency.


Aside from light and heat, your windows should also protect you against noise pollution. This is particularly important if you leave close to highways, airports or other high-acoustic areas. Sound transmission is directly connected to air leakage as they both depend on how airtight your home is. You can also improve your sound protection by ensuring the proper installation of your replacement windows.

Don’t trust roofing companies that overpromise and underdeliver. Our professionals at All American Roofing are committed to helping you find the right environmentally friendly and energy-efficient home exterior products for your needs. Call us today at (405) 787-0400 or fill out our online contact form to request a free consultation with one of our experts or to learn more about how we can help you today. We serve Oklahoma City, OK.