What changes
Double glazing uses two panes separated by a sealed cavity. Triple glazing adds another pane and cavity. Coatings, gas fills and spacers also influence thermal performance, so pane count alone is an incomplete description.
Consider the complete opening
Compare the declared glass and whole-window values, then review daylight, solar gain and the chosen opening system. The useful question is how each complete configuration responds to your project brief.
Prepare a useful comparison
Ask for both proposed glass build-ups in writing, including thickness and weight. Have the system supplier confirm their suitability for the selected frame, hardware and dimensions before settling the specification.
