Daylighting
Decrease energy use. Boost morale and productivity.
Daylighting is the use of natural light, through skylights and windows, to complement or replace interior electric light. Daylight is different than sunlight, which is a direct, often glare-producing beam. It is available on even the cloudiest day in Vermont. With appropriate controls, you can modulate how much daylight enters your space.
Benefits of daylighting:
- Daylighting creates pleasant, attractive spaces in which people feel good. Daylight in retail shops can encourage customers to visit more often and to purchase more products. In classrooms, students concentrate better with natural light. Workers in naturally lit commercial buildings experience improved morale and can become more productive.
- Daylighting reduces energy costs by turning off or dimming electric lights when possible. Cooling cost savings are also possible, due to the reduced use of heat-generating lights.
- Buildings that make use of natural light may lease at better rates, have reduced tenant turnover, and greater resale value.
When you build or renovate:
- Start early. Incorporate daylighting strategies in the pre-design phase of the project and contact Efficiency Vermont for the greatest cost-effectiveness.
- Determine daylight feasibility when doing space planning. Your architect can assess window-to-wall ratio and whether or not windows are obstructed. Then, you can determine how much natural and electric light you'll need.
- Include daylight in decisions on building structure and rooms. Reduce glare by positioning windows and skylights away from the most direct sunlight. Plan skylights in long and narrow rooms, in conjunction with dimming fixtures, to optimize the spread of light. Dimming is most effective in rooms with windows facing north or south.
- Select the right glazing. When selecting glazing pay close attention to visible transmittance, visible reflectance, solar heat gain coefficient, and U-Value.
- Consider the whole building. Your daylighting decisions may reduce the number of heat-generating lights needed in your building. By reducing the number of light fixtures, you'll lower your cooling needs and reduce the size of the cooling system you'll need. Conversely, daylighting and associated glazing can increase your heating needs if not designed appropriately. Talk to your architect, engineer, or lighting designer.
- Coordinate lighting. Design lighting systems so they accept dimmable ballasts and sensors. These technologies respond to available daylight and provide only as much illumination as you need.
When integrating daylighting controls, consider the following tips:
- Install switching or automatic dimming for fixtures in the “daylighted zone,” usually within 12' from a window wall. Fixtures located in a daylighted zone may require separate switching per Vermont state code.
- In spaces smaller than 400 square feet, provide separate switches for the light fixtures in the daylighted zone and connect them to a vacancy sensor – a type of occupancy sensor that requires manual on.
- In spaces greater than 400 square feet, consider daylight-controlled fluorescent step or dimming ballasts. Switching or “step-dimming” systems are typically more cost-effective than continuous dimming systems and can be used in common areas. Continuous dimming should be used in working spaces in order to prevent distraction to employees.
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