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resources > design information
Here we provide some basic information and explanation on daylighting design. In addition to the information provided here, there are technical books, training courses and research results to help you understand daylighting design (visit the Resources and Training menus above).
How to daylight
Daylighting is a systems approach. Daylighting isn't simply a thing you add to a design. It is a central design tenet that drives the entire design of buildings and considers the following:
- Orientation and footprint
- Climate, region and general availability of natural light
- How Buildings Use Energy (This link will launch a Flash-based tool. When the window opens, click the arrow in the right-hand corner to launch.)
- Urban vs. suburban
- Floor to floor/floor to ceiling heights
- Window to wall ratios
- Placement of glazing
- Toplighting, sidelighting or both
- Glazing performance (visible light transmittance, etc.)
- Exterior shading and solar control
- Interior shading and solar control
- Integration with electric lighting systems (lighting power densities, controls and electric lighting design)
- Reduced cooling loads (note: discuss cool daylighting)
- Interior design (color, reflectance, furniture selection)
- Floor plan (how far will daylight penetrate?)
The basics: toplighting and sidelighting
Toplighting brings daylight into the building from above through clerestories, skylights, tubular skylights, sawtooth designs, etc. Daylight that enters the building above 10 feet, even if it's through a vertical opening, is referred to as toplighting.
Sidelighting brings daylight into the building from the side through windows, curtainwalls, etc.
How-to topics:
- calculate depth of a light shelf/shading device
- calculate daylight factor
- calculate lighting power density
- decide what light to solar gain ratio you want
- choose which daylighting control system is appropriate for your space/building
- how to calculate how far daylighting will penetrate into a space from a window
- calculate glazing factor
- how to get LEED points for EA credits as well as views
- how to use a sun-path diagram
Do's and don'ts of daylighting
Do set an energy performance goal for your project.
- In addition to the beauty and aesthetics of daylighting, the most significant benefit is the reduction in energy usage for both lighting and cooling of a facility
- What is an energy performance goal? Usually a whole building goal in kBtu/ft2.
- This can also be done on a system by system basis—specifically for lighting power densities and square feet per ton of cooling. Setting these system goals will help you achieve an overall whole building performance goal.
- Lighting power density is Watts/square foot. Make sure to include the ballast factor in your calculations to ensure they are accurate.
- Setting a goal for square feet per ton of cooling provides the design team with a goal. The team may not always be able to meet the goal, but knowing there is a performance metric can often help keep a system from being dramatically oversized.
Don't do daylighting without controls to manage the electric lighting levels.
Do understand basic lighting design elements before jumping in headfirst.
Do understand that daylighting is a systems approach.
If you fail to consider one element, your design can be seriously compromised and all you work for naught. The owner, the entire design team (HVAC, architectural and EE) and the contractor need to understand the goals of the design. If everyone is not in the loop, you may find those daylighting controls or solar shades value engineered right out of the project leaving you with glare and no energy savings.
Don't underestimate yourself or your team.
You can do this. We used natural light for thousands of years before Thomas Edison came along. Logic is your best tool in addition to communication.
Do get some basic software and training to help give you basic daylighting design rules and strategies.
Basic software tools help you analyze your design and give you confidence in your strategies. In many parts of the country there is technical assistance support to help analyze your design, as well.
Don't believe there is only one way to daylight a building.
There are many different strategies, solutions and issues for various building types, climates and locations. Basic principles apply but how you achieve those performance metrics can vary widely.
