During the day you should be able to walk throughout the house into all rooms without turning on a light. The science of lighting is very technical and there are many calculations that can be made to determine the correct amount of light in a room. There is however, a rule of thumb which most designers use;
A minimum of approximately 20% of your wall space in each room should be glazed.
This will of course depend on the orientation of the window and use of the room. Dont follow this rule blindly; it is simply a guide to make sure that each room has a natural light source and ventilation opportunity.
When planning for natural light keep in mind;
The orientation of the window
What time of day/year direct sunlight will enter the window
What type of glass is fitted in the window- single or double glazed, Tinted or low-e glass
The shading device fitted inside or outside
Will there be any glare from surfaces underneath the window
The size of the room to be lit
The colour of the walls and ceilings
For more information on natural lighting see
Windows
Artificial Lighting
You can make or break the feel of a room with the choice of artificial lighting fixtures.
Always consider the following in determining the right lamp for an application;
Light output required " low/high
Colour temperature " cool/warm
Colour rendering " important or not
Operating hours " short/long
Lamp options available that would suit application
Lamp running cost
Cost of the lamp
Replacement frequency, difficulty and cost
When planning consider;
The electrical set out for the lights
If mounting lights on the wall it is best to have lamps opposite each other across the room.
If you lamps will be on the ceiling consider whether they will be set flush or hanging down,
If so how low will they be?
What will they hang over?
What kind of shades will fit over the lamp type?
Places for standing lamps and table lamps
Do you need direct light?
If lamps are over head they can cause shadowing on tasks
Over bench lights will provide good task lighting
In cupboard lights are good for pantries and for aesthetics in display cabinets.
Design 
