Choosing The Right Glass

Replacement Glass Value’s & Definitions

The key to choosing the right glass system for your home is to find the right combination of performance values to suit your needs. But you may have come across several window terms you are not familiar with.

U-Value, Solar Heat Gain and Visible Transmittance – these important factors should be weighed when choosing windows for your home. They all interact with one another to create a harmonious product that is right for you.



U-Value is the measure of the rate of non-solar heat loss or gain through the windows. The lower a U-Value, the greater a window’s resistance to heat flow, and thus the better its insulating value.

Solar Heat Gain Co-efficient (SHGC)

Solar Heat Gain Co-efficient, or SHGC, is a description of the the fraction of solar radiation admitted through a window including what is absorbed and subsequently released inward. The lower a window’s SHGC, the less solar heat the window transmits and the greater its shading ability.

Visible Transmittance (VT)

The Visible Transmittance, or VT, measures the fraction of the visible spectrum of light weighted by the sensitivity of your eyes that is transmitted through the window. Simply put, it represents the amount of daylight that the window allows to shine in.