Glass Low-E Coatings, Temperature Control, and Energy Efficiency for Title 24 Compliance Explained
Updated: Nov 13, 2020
The Most Important Factors When Determining The Energy Efficiency of Glass and Title 24 Compliance
(VLT): Visual Light Transmittance : Measurement for how much visible light and invisible ultraviolet light passes through (0%-100%)
(SHGC): Solar Heat Gain Coefficient : Measurement for how much solar radiation or heat passes through the glass to the interior of the building :
(0.00 - 1.00) Depends on the climate but typically the lower the # the better
(U-Value) Thermal Transmittance : The measurement of heat loss and insulation. How well the glass retains temperatures (heat during winter and cool air during summer). Lower ratings mean better thermal insulation.
(LSG) Light to Solar Gain : This is the measurement of the ratio of light passing through to the amount of heat. A higher LSG ratio means sunlight entering the room is more efficient for lighting during the day, especially for summer conditions where more light is desired with less heat gain. (Least important of the 4 but still notable)
Factors That Affect Energy Efficiency
-Type of Low E Coating (Major Impact)
-Type of Glass (Major Impact)
- Glass Color/Tint (Moderate Impact)
-Type of Spacer (Minor Impact)
-Spacer Size (Minor Impact)
-Type of Gasses In between Spacer (Minor Impact)
Low-E Coatings Explained
What is Low-E?
Low Emissivity film is a microscopic coating that is applied to glass to minimize the amount of infrared and ultraviolet light that comes through, reflect heat, and improve the overall energy efficiency of a structure.
Differences in Low- E Coatings
Across the United States there are different glass manufacturers that all have their own name for their specific version of Low-E films such as Solarban, LoĒ, SN/Super Neutral, SunGate, ClimaGaurd, SunGaurd.
Here at Artisan Glass & Design we primarily use Vitro Architectural Glass who uses Solarban Low-E film.
Variations include: Solarban 50, Solarban 60, Solarban 67, Solarban 70, Solarban 72, Solarban z75, Solarban 90, Solarban R100
Each variation has a different color, transparency, and overall reflectivity as well as increased performance metrics the higher you go. But better performance also means an increase in price so we help find the balance that meets your title 24 efficiency requirements as well as your budget and design needs.
You can use this link to test out for yourself different configurations and see their performance specs.
When installing new windows or doors there are many options for what glass type to get installed but when it comes to temperature control energy efficiency and meeting title 24 requirements insulated glass units (as shown in the first picture above), are your best option.
Insulated glass units are typically made up of 2-3 pieces of glass separated by an aluminum spacer. The space in between is filled with a special blend of gasses typically argon and oxygen, and covered with a Low-E coating.
For us at Artisan Glass & Design Solarban 70 is the most common variation of Low-E coatings as it meets many performance requirements while still keeping costs low.