With much concern about energy efficiency, homeowners are keen on having the right windows that will help them lower their cooling and heating bills. Every time you buy a window or when you are conducting your research, you will always come across all those energy labels, and most people never know how to ready them, or sometimes what they mean.

However, every writing and figure you see on the labels, have a meaning, and it is vital to know what to make out of them, so that you choose the correct window type. Here are some of the important labels and what they mean:

The Energy Performance Rating – The U-Factor

This refers to the rate at which, a building loses heat in terms of the U-value. The U-factor ratings for windows, normally falls between 0.2 and 1.2, and the lower the value, the more energy efficient the window is. It is one of the most important labels concerning insulated windows.

The Solar Heat Gain Coefficient – SHGC

The SHGC reveals how efficient the window is at blocking the heat from the sun. It is calculated as a fraction of the incident solar heat radiation, passing through the window, gets absorbed, and is ultimately released into the room. The coefficient is expressed as a number between zero and 1, with the lower number representing a better grade than a higher value. This is another label you should watch out for, pertaining to insulated windows.

Visible Transmittance – VT

This is an optical property, which illustrates the amount of visible light passing through the window. It is also expressed as a number between 0 and 1, and the higher the value, the higher the amount of light passes through the window.

Air Leakage – AL

This refers to the amount of air passing through a square foot of window, and is calculated per square foot. Heat can be lost or gained through cracks in the window, and the lower the air leakage value, the more energy efficient the window is.