Glazing Performance
What is U-value in windows?
By Sheng Xu · 19 July 2026
AI-generated illustrative image. Not a product test, certification record or project evidence.
U-value measures how readily a window conducts heat, indicating the rate of non-solar heat loss or gain through the entire window assembly, including glass, frame, and seals. A lower U-value signifies greater resistance to heat flow, meaning better insulation and improved energy efficiency. This 'whole window value' is crucial for meeting National Construction Code (NCC) compliance and selecting appropriate windows for Australia's diverse climates.
Why it matters
Window and door decisions are rarely about one metric in isolation. Standards, glazing, frame selection, installation conditions and project documentation all need to work together before a system is selected for a real site.