Day lighting is the controlled admission of natural light into a building to reduce electric lighting and save energy. It provides psychological benefits like improved well-being and productivity as well as energy savings of up to one-third of total building costs. The design goals of day lighting are to provide adequate light quality and quantity throughout the space while integrating with building systems and achieving cost effectiveness. Artificial lighting must also be integrated to effectively provide energy savings from day lighting. There are various energy efficient techniques for day lighting like window placement, shading, and lighting controls.

1. WHAT IS DAY LIGHTING?
“Day lighting is the controlled admission of natural light, direct
sunlight, and diffused-skylight into a building to reduce electric lighting and saving energy. By
providing a direct link to the dynamic and perpetually evolving patterns of outdoor
illumination, day lighting helps create a visually stimulating and productive environment for
building occupants, while reducing as much as one-third of total building energy costs”.
WHAT ARE THE BENEFITS OF DAYLIGHTING?
The two primary reasons for using daylight to meet the illumination requirements:
 Architectural space are the psychological benefits and
 Energy savings benefits.
Good day lighting has been shown to improve the overall attitude, satisfaction and wellbeing
of building occupants.
A number of research studies variety of benefits of day lighting in different building types and
functions:
 Increased worker productivity and reduced absenteeism in office buildings,
 Improved student educational performance in K–12 schools,
 Improved patient recovery times in hospitals.
 Exposure to daylight has also been shown to improve general health and circadian
rhythm.

2. WHAT ARE THE DESIGN GOALS OF DAY LIGHTING?
1. Quantity
Provide ambient lighting requirements during daytime hours for the majority of the year.
2. Quality
Create uniform distribution of daylight to reduce uncomfortably high brightness ratios.
Control direct sunlight when necessary and utilize beneficial passive solar strategies
when appropriate.
3. Usability
Allow for user adjustment and override.
Ensure adequate daylight to all occupants of the daylit space.
Provide view and connection to the outdoors.
4. Building Integration
Fully integrate with the architectural expression of the building inside and out.
Fully integrate with other building systems -- HVAC, Electrical, Lighting, Structural,
Interiors.
5. Cost Effectiveness
Implement within overall construction budget of the project.
Achieve significant energy savings by reducing lighting energy costs and associated
cooling energy costs.
WHAT IS THE IMPORTANCE OF ARTIFICIAL LIGHTING AND ITS
INTEGRATION WITH DAY LIGHTING?
Along with adequate solar control, integration with the electric lighting
system design of a space is essential for a day lighting design to effectively provide increased
building-wide energy savings.
The following electric lighting system design strategies should be considered for non-day lit
spaces as well as daylight spaces. These will help to lower the Lighting Power Densities (LPDs)
of the various spaces and reduce energy use while maintaining the required light levels.

4. ENERGY EFFICIENT METHODS FOR DAY LIGHTING:
The dynamic nature of daylight throughout the day and throughout the year poses numerous
challenges when designing buildings to take advantage of natural light and save energy.
Following are a few of the techniques available:
 Window size, shape, position, and orientation
 Windows assemblies (frame and glass) with low u-values and low SHGC
 Shading devices
 Light shelves
 Sloped ceilings
 Skylights and roof lights
 Atrium spaces
 Light wells
 Fibre optic cable networks connected to rooftop light traps
 Tubular daylight devices (sun pipes)
 Reflective or pale painted surfaces and interior decor
 Daylight responsive electric lighting controls