Glass & Energy

Solar energy contains different wavelengths of energy including ultraviolet radiation, visible light and infrared heat. Each type of light is reflected, absorbed and transmitted by the glazing. The critical elements and desired values for each type of light will vary between applications. A wide array of products exists to help you achieve the desired results.

Laminated products are extremely effective in blocking UV transmission. Tinted products reduce transmission by increasing absorption. Reflective products reduce transmission by increasing reflection.

In sealed insulating glass units, low-e products greatly reduce heat transfer by reflecting radiant heat back towards the source. Filling the airspace of a sealed insulating glass unit with a heavy gas, such as argon, will further improve insulating values.

Common measures of performance for a glazing include the following:

  • Visible Light Transmittance: In the visible spectrum (380 to 720 nanometers), the percentage of light that is transmitted through the glass.

  • Visible Light Reflectance: In the visible spectrum, the percentage of light that is reflected from the glass surface(s).

  • Solar Energy Transmittance: In the solar spectrum (300 to 2100 nanometers), the percentage of ultraviolet, visible and near infrared energy that is transmitted through the glass.

  • Solar Energy Reflectance: In the solar spectrum, the percentage of solar energy that is reflected from the glass surface(s).

  • UV Transmittance: In the ultraviolet spectrum (300 to 380 nanometers), the percentage of ultraviolet energy transmitted through the glass.

  • U-Value: The overall coefficient of heat transmission or thermal conductance (air to air) of a material or combination of materials, across which there is a temperature differential. The heat loss (or gain) of any fenestration is expressed in Btu per hour per square foot, and is the result of multiplying the U Value times the difference between the outdoor and indoor temperatures.

    Summer U Values are based on an outdoor temperature of 89F (32C), an indoor temperature of 75F (24C), a solar intensity of 248 Btu/(hr x ft2), (789 W/m2), and a 7.5 mph (12 kph) wind.

    Winter U Values are based on an outdoor temperature of 0F (-18C), an indoor temperature of 70F (21C), a 15 mph (24 kph) wind velocity and no sun.

  • Shading Coefficient: The ratio of the solar heat gain (using summer conditions) through a specific fenestration divided by solar heat gain for a lite of 1/8" (3mm) clear glass.

  • To view performance value charts for the much of the glass that Solar Seal stocks, please click here.