A reader writes: I have a loft with a southern exposure and only 2 1/2 windows, it is a long space extending back from the windows and the area farthest away can get quite dark, especially if the sun isn't shining. What can I do to get natural light deep into the space?
This is not a new question; before the age of electric light it was a major issue in design. In the 19th century it was very common to use prism glass; for clothing stores in particular, gas lighting would produce soot that could damage the goods.
You can still find prism glass in the occasional store; I walked into one in Toronto a few weeks ago and was just amazed, the employee was sitting forty feet back from the door in full sunlight.
Computerized mirrors that follow the sun are usually big things; the Structured Surface Physics lab of the University of British Columbia has miniaturized the concept and stuck it on the face of buildings. They have developed a an array of mirrors with computer controlled servos that track the sun. This technology has become so cheap that it is no more than a couple of bucks per unit. See more at SunCentral Computerized Mirror Array Brings Daylight Deep Into Buildings
Parans, a new Swedish company, has developed a system of collectors, fibre optic cables and elegant luminaires to transport natural light just about anywhere in a building, so that nobody should have to go for a day without sunshine. More here An Australian system, DayRay, appears to have never made it to market, so there does not appear to be an economical fiber optic system available in America.
Light shelves can be installed inside or out of a window, and bounce the light off the ceiling instead if having it all fall on the floor. From Queens University, talking about office installations:
For best results, light shelves should be mounted horizontally. If the surface of the shelf is highly reflective, then the angle that the sunlight is reflected onto the ceiling will be equal to the angle of incidence of the incoming sunlight.For a more diffuse spread of light, shelves can be painted with rougher, less mirror-like materials. This will scatter the light at many different angles, providing a more diverse coverage area on the ceiling. The ceiling should be painted with a reflective paint in a light colour, to bounce the light back down onto the work area.
Geof Gainer, the Actual Size Architect, built his own interior light shelf with an IKEA Mirror. He writes:
A surprisingly effective way to draw light into a room is by use of a light shelf. These horizontal reflectors are mounted either inside, outside, or on both sides of a southerly-facing window. Sunlight bounces off the surface and onto the ceiling within. Any bright surface will diffuse daylight effectively.
This looks economical, effective and DIY. Geof tests his installation with a light meter and it is very effective. In the end, the IKEA mirror hack is probably your best bet. More at Tech Note: Light Shelves