Standard vs Off Standard Louvre Window Heights
Standard heights do exist and are based around the chosen louvre blade height of 102mm and 152mm. Multiples of these blades give standard window heights. Off Standard heights are available but this will add cost and result in a fixed louvre blade to act as a filler piece.
The type of window frame chosen will also affect the standard heights. Proprietary frame height will be based on the sizes for Altair Louvres plus an allowance for the outer frame type chosen. This is best discussed with your window fabricator and builder.