Lighting terms may need defining before we get started. First, a watt is the rate at which electricity is used. The government has required that incandescent bulbs be discontinued because they use a lot of watts for the amount of light that is given. Light on a given surface is measured in footcandles. When we are trying to read the newspaper, we want to make sure whatever light source we have is giving us enough light to avoid eye strain. The quality of light is measured by the number of Kelvins – warm incandescent is rated at 3,000 Kelvins, a halogen is somewhere around 3,200, cool fluorescent at 4,000, and daylight is 5,200 Kelvins. We can also measure the CRI or Color Rendering Index with the sun as our reference. A rating in the 80-100 range is best. Incandescent is at 100. Standard fluorescent is poor at 62, although a “warm” fluorescent can get close to 90. We’ve all seen the blue light given off from standard, cool, fluorescents and the distortion of the true colors in the area surrounding. Fluorescents also have disposal issues so LED looks to be the bulb that will set the standard for the future. LED’s have been developed with a CRI at 90 or above to give good color rendering and still have the energy efficiency needed to meet today’s standards.
All rooms should have multiple layers of light: General, ambient light can be accomplished with can lights, surface mount, or track lighting. Task lighting can be pendants, pucks, strip, or mini track lights. Accent lighting can be focused on a special feature in the room and might be accomplished with sconces, tape lighting, and directional track or cans. Decorative lighting can sometimes serve the same purpose as these 
other types of lighting with table lamps or chandeliers perhaps. Multiple layers of lighting give flexibility to the lighting scheme and allow for many different scenes to be set. I always suggest dimmers as I feel it’s best to have the maximum available light installed and be able to dim it down since adding additional light can be a costly redo. I also don’t feel it is absolutely necessary to have symmetry in the position of the cans in a ceiling. Its more important to have light where you need it. If recessed lights are placed 24″ from the wall in a standard kitchen layout, the user will have better light available on the counter area, rather than from behind as is most often done. Symmetry is certainly critical in any decorative lighting that might be used in the room, however.
According to the National Sleep Foundation, 30 – 40 percent of adults say they suffer from occasional insomnia. 10- 15 percent of adults say they have chronic insomnia. Light can play a big role in getting a good night’s sleep. Warm sunlight triggers chemicals in our brains that wake us up. That is why is is often easier to wake up in the summer than the winter. The hormone melatonin is needed for our brains to induce sleep. Artificial light at high levels all day can disrupt the production of melatonin. Use a light source that simulates bright morning light as soon as you wake up. A sun lamp for 15 minutes might help. Lower light levels and also warmer light with a CRI of 2700 Kelvin is recommended for the last couple hours before bedtime in the evening. 40 watt incandescent bulbs will work well for this purpose.