Getting nice warm office lighting can get pretty expensive in SG, as ambient sunlight comes with a high heat transport cost here. One thing my architect step-bro pointed out is that one can use light tubes to get an on-average correct amount of light into a space. Haven't seen any installations here beyond the courtyard approach, though.

My parents run a light-tube installation business in Portland, OR -- so I've run into a fair number of them. They can work very, very well, but not all light tubes are equal. The design of the tube and the diffusers play a large part in both efficiency and utility (respectively). Anecdotal, but it seems like the smooth-sided tubes work more efficiently (SolaTube uses that design). Some tubes use an articulated flexible material that looks a lot like a dryer hose. I suspect that the angle of incidence in the irregularly formed tube walls deflects a substantial amount of light away from the room. I imagine there is hard evidence out there--I haven't bothered to look. --Rogan