Views: 0 Author: Site Editor Publish Time: 2026-09-17 Origin: Site
U-Factor, SHGC and Visible Transmittance are more than technical numbers. For U.S. building projects, they help buyers compare window and door performance and select a configuration that better matches climate, glazing and project requirements.
When sourcing aluminum windows and doors for the U.S. market, buyers often see terms such as U-Factor, SHGC and VT on performance documents and product specifications.
These values help describe how a complete window or door performs. Understanding what they mean makes it easier to compare different configurations and communicate project requirements clearly with suppliers.
NFRC ratings provide standardized performance information for windows, doors and skylights. The most commonly reviewed values include U-Factor for heat transfer, SHGC for solar heat gain and VT for visible daylight.
U-Factor measures heat transfer through the window or door assembly. In general, a lower U-Factor indicates better insulating performance.
For aluminum systems, the final result can be influenced by the frame design, thermal break, insulated glass, spacer and complete product configuration. This is why glass performance alone should not be treated as the performance of the complete window.
Solar Heat Gain Coefficient measures how much solar heat enters through the product. The value ranges from 0 to 1.
Lower SHGC can help reduce solar heat gain, but the lowest number is not automatically the best choice for every project. Climate, orientation and building design should be considered together.
Visible Transmittance describes how much visible daylight passes through a window. A higher VT generally means more natural light enters the building.
However, Low-E coatings, tinted glass and other glazing configurations can affect both daylight and solar performance. For project selection, VT should therefore be reviewed together with U-Factor and SHGC.
Similar-looking windows can have different performance values when the frame, glass, gas fill, coating, grids or other configuration details change. Buyers should therefore verify the performance of the required product configuration rather than relying on one component.
Provides standardized ratings and certification used to evaluate fenestration energy performance.
Uses certified performance data and additional program criteria to determine whether eligible products meet ENERGY STAR requirements.
A clear window schedule and performance requirement can reduce unnecessary specification changes later in the project.
Do not assume that one rating automatically applies to every glass, size or configuration in a product family. When performance is important to the project, confirm that the proposed configuration corresponds with the applicable supporting documentation.
A lower U-Factor generally indicates better insulating performance. The required value should still match the project's climate, specifications and applicable requirements.
No. Lower SHGC means less solar heat gain, but the appropriate value depends on climate, orientation and building design.
Not necessarily. Low-E glass is one part of the system. Frame design, thermal breaks, glazing configuration and other components can influence complete product performance.
NFRC ratings make window and door performance easier to compare, but the right specification depends on the complete product configuration and the requirements of the building project.
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