The U value indicates how well a window conducts heat. The lower the U value, the greater a window’s resistance to heat flow is and its insulating value. It is usually represented as a value between 1.0-10.0 W/m2.K, with 1.0 having superior insulation properties.
This translates to your home being cool in summer and warm in winter!
Solar Heat Gain Coefficient
SHGC is the measure of how well the window blocks heat caused by the sun. SHGC is represented as a number between 0 and 1- the lower the SHGC, the less solar heat it transmits.
A very low SHGC is not always ideal as it will lead to a comfortable summer but less solar warmth during winter. An ideal SHGC for year-round comfort is roughly 0.5.
Visible transmission controls how much natural light enters your home through the windows. Visible transmission can be represented as a percentage- the higher the percentage the more natural light will enter.
A high visible transmission percentage is optimal with a low U value as it will give you a comfortable temperature without sacrificing natural light.
UV transmission refers to the amount of UV that is transmitted through the windows. A common myth is that all windows protect you from harmful UV rays when you are indoors but this is not true.
The lower the percentage, the less UV rays will transmit and the more protected you will be.
Sound insulation is measured in decibels (dB). When referring to sound insulation, the number of decibels quoted is the amount of noise reduction they can achieve.
For example, a sound insulation coefficient of 40dB equates to a loud radio becoming as quiet as moderate snoring!