Down lights, mounted in the ceiling, are becoming increasingly popular for living areas, kitchens and bathrooms. A great advantage of recessed downlights is that they give even, gentle, low shadow lighting within a room, especially when used with compact flourescent bulbs.
The bulb in the fitting is contained within the downlight unit in the void space above the ceiling. In a good quality downlight the housing (or "can") is normally sealed to avoid the bulb acting as a chimney; if the can is not sealed, when the bulb gets warm, air is drawn up into the void above the ceiling. If you have downlight units that are not sealed then you should (and must in some cases) install a fire hood over the fitting.
Most modern fittings are held in place by simple spring clips that push against the 'back' of the ceiling when the fitting is pushed up into the ceiling from below. Removing the fitting is easy as can be firmly pulled out of the ceiling, to as far as the cable will allow.
Downlights can be mains powered or low voltage (typically 12 volts) but 'low voltage' does not mean 'low energy'. Installing LED products is the best option as this will make real savings on the amount of energy that you use to run the fittings. Many LED downlights are supply with their own mains powered driver to ensure a perfect match between the driver and the LED.
Most recessed down lights used to use halogen bulbs, these give a fair bulb life. Typically mains bulbs used are 35 or 50 watt while low voltage systems use 20-50 watt - each giving similar levels of illumination.
Halogen bulb, mains and low voltage downlights can be dimmed using normal light dimmers, althought with low voltage you must make sure that your transformer is compatible with the dimmer switch.
For a few years, compact fluorescent (cfl) bulbs were available which gave better bulb life (5,000 - 8,000 hours) but often had at least a minute of 'warm-up' time (the time taken to get to their full lighting potential). Fluorescent spot light bulbs have now been superceeded by LED products.
LED bulbs are now a much better choice for spot light / downlight options as they are extremely low powered (often 3w - 8w), have a manufacturers suggested average lifetime of 20,000 - 30,000+ hours and are at full brightness as soon as you flick the light switch.
Other downlights are available that use a screw in type bulb. These are available in various sizes including 50mm, 63mm and 80mm. There are low energy downlight equivalents spot light bulbs for these lights too.
Obviously the best way to save power, and reduce your electricity bulbs is to turn your lights off when you dont need them. However, the latest LED bulbs can produce a huge amount of light while using a very small amount of power. The latest LED bulbs, are at least as bright as an old 50w halogen bulb in terms of brightness.
For general, ambient lighting, downlights should be positioned about 5 - 7 ft (1.5 - 2.1 m) apart in both directions (i.e. across the room as well as along the room). Before deciding on the spacing, check the position of the joists above the ceiling - you want to use a spacing which will position the downlights between joists.
Don't overload your existing electrical wiring! Most mains house lighting circuits can handle 400 watts per room, this allows for up to 8 x 50w halogen downlights, OR up to 40 x 10w cfl downlights OR over 130 x 3w LED downlights per room per circuit. If in doubt, consult a qualified electrician.
Be careful choosing downlights for bathrooms! They need to conform to the electrical regulations which depends upon their actual position - see bathroom electrical zoning page and the fire rated downlights information below.
Fire rated downlights resist the spread of a fire through the holes cut into a ceiling. Building regulations specify that this type of fittings must be used in some locations, for example where a habitable room is above.