The following guidelines are based on practical rules of thumb and may be helpful in planning how to place your lights.
For general lighting in the home downlights with the equivalent of a 100watt incandescent are a good choice. New downlights have been designed for compact fluorescent lamps which can save up to 80% of the power required for a conventional incandescent bulb. If fluorescent lamps are not suitable for any reason there are halogen lamps available as replacements for conventional bulbs which save 30% of the power and are dimmable.
The spacing of these downlights should be about three quarters of the height of the ceiling, e.g. if the stud height is 2.4 meters then space the lights at 1.8 meters.
An attractive alternative although more expensive is to use a combination of single and multiple low voltage downlights
These distances are conservative and take no account of the light fittings design. The data sheets of most lights give an SHR figure. This is the maximum space to height ratio for the spacing of that light. To find the spacing multiply the SHR by the height of the light. eg 8 foot stud, SHR 1.25 the spacing would be 8 x 1.25 = 10 feet.
Halogen lights are used for lighting working areas such as kitchen, laundries and bathrooms because of the quality of light they produce. An advantage of 12 volt halogen downlights is the variety of bulbs available.
Halogen lamps are available in 20watt, 35 watt and 50 watt and special fittings take 100 watts, but the advantage is that each is available in beam angles of 10, 24, 36 and 60 degrees. This means that you can change the bulb to get a narrow beam or to spread the light.
The spacing of 50 watt halogen lights should be about half of the distance from the bench to the ceiling. e.g. if this distance is 1.4 meters then the lights should be spaced about 0.7 meters apart, or half the distance from the floor to ceiling for general lighting.
Highlighting a wall can make a room appear larger, or used in an entry can make the hall seem inviting.
Halogen 50 watt lights are usually used and these are spaced about one quarter of the height of the wall out from the wall. The lights are spaced about the same distance apart along the wall, and tilted to shine about one quarter of the way down the wall.
If a wall has an interesting texture, then grazing it with light is a popular option. In this case 50 watt halogen lights are fitted about 300mm out from the wall and spaced about 450mm apart along the wall.
Highlighting a painting is usually done with a halogen 50 or 35 watt light. If the light is recessed into the ceiling place it in line with the centre of the painting. The distance out from the painting should be about two thirds of the distance from the centre of the painting to the ceiling. Make sure that the halogen bulb has a UV filter or the light will bleach your painting.