Before I started in a more buildings-focused electrical engineering position, I didn't think that much went into selecting lights for buildings. Once you first get started in lighting design, it is like opening a can of worms, there is so much detail that goes into lighting design, it's unfathomable.
First of all, lighting design in Australia is dictated by AS1158. Not only does the Australian standard explicitly state illuminance requirements for rooms based on their task (eg 320 lux for office based tasks), it also clearly defines how to calculate these levels based on the environment.
What really is lux? Lux is the SI derived unit of illuminance and luminous emittance, measuring luminous flux per unit area. It is equal to one lumen per square meter. Luminous flux? Lumens? What do all these terms mean? A lumen is the SI derived unit of luminous flux, which is a measure of the total amount of visible light emitted by a source.
Now when it comes to designing lighting for a building/area, multiple large considerations must be taken. Once you have determined what tasks will be completed within the area you are designing, you must then go to AS1158 and determine the required lux requirements. Following this, you must ensure you have accurate dimensions of the area you are designing for, along with all reflectance (colour) of surfaces within the area.
Once you have got all these parameters, it is time to begin modelling the area within any lighting design software package (eg AGI-32). Now the designer must select lights (luminaires) to be specified for the area. The designer must take into consideration the ceiling (if there is one) type, this will dictate how the luminaires are to be mounted, be it: surface, recessed, suspended or pole mounted.
Most luminaire fitting manufacturers will provide photometric files (IES files) detailing how their respective lights would behave if they were installed in the design area.
Once the designer has verified that the specified luminaires will meet required lux levels in the area, this design must be passed to the electrical designer as they must factor in how much power all the luminaires will require to operate and how the cable routes must be laid out to suit the luminaires on the site.
Please note, that this is a very simplistic view at lighting design. Just like any area of work, there is an art to doing a proper job.