Direct answer
Triple glazing is not always necessary. It may be useful in cold areas, exposed façades or highly efficient homes. In mild climates, good low-emissivity double glazing can be very balanced.
When double glazing is enough
It is usually enough when upgrading old windows, improving comfort and keeping the project controlled. Cavity, low-e coating and solar control matter a lot.
When to consider triple glazing
Consider it for cold orientations, mountain areas, passive-house goals or large glazed surfaces, provided the frame and hardware can handle the weight.
Noise and glass
For noise, asymmetric thicknesses, acoustic laminated glass and airtightness can matter more than simply adding a third pane.
What to request in the quote
Ask for full glass composition, thickness, cavity, low-e treatment, solar control, thermal and acoustic performance and system compatibility.