Day Light Harvesting
By Greg Amato for Bay Screens and Shades
and lighting specialists are increasingly turning to day lighting as a primary source of
illumination in mainstream construction. Day lighting will provide tremendous operating cost
reductions if properly integrated with an electrical lighting control system.
At the same time, proper day lighting can increase the comfort and productivity of a
building’s occupants. It provides superior quality light for a wide range of tasks in the
workplace. Windows, skylights and other clearstories used for daylight integration can also
improve ventilation, lower air conditioning costs, and provide workers with visual
stimulation. Exposure to both daily and seasonal cycles of natural daylight has also been
shown to positively affect both the mood and stress levels of occupants.
For successful daylight integration, certain principles need to be followed in terms of
optimum building placement: the location, design and selection of materials for fenestration
(windows, skylights, etc.) and electrical lighting design. In general, the earlier in the design
process of new buildings that day lighting issues are addressed, the more successful the
daylight harvesting project will be. To take full advantage of daylight integration, buildings
should have automated controls that either turn off or dim artificial lighting in response to the
available daylight in the space. This is traditionally called “daylight harvesting.”
Advantages of day light harvesting
Greater Health, Well-Being and Productivity
There is strong evidence that day lighting can improve the health, well-being and productivity
of occupants. Daylight generally has a high colour temperature, high colour rendition and is
rich in blue radiation. Both good colour identification and improved visibility are attributed to
these factors. People generally describe daylight as providing better visual clarity and colour
differentiation. One 2003 study of office workers in California confirmed that workers
exposed to daylight through a window with a view versus those with no window performed
10-25% better on mental functioning and memory recall tests. On the other hand, the study
also found that glare from windows was associated with poorer office worker performance.
Greater glare caused performance on three mental function tests to decrease by 15-21%.
Clearly, day lighting needs to be carefully planned to reap its benefits while avoiding the
Increased Energy Savings
With lighting accounting for approximately 38% of all energy consumed in modern
buildings, daylight harvesting can significantly lower energy costs by providing illumination
while allowing electric lighting to be automatically dimmed or switched off. Daylight
harvesting also produces a lower cooling load than electric lighting for the same amount of
illumination, resulting in lower cooling costs. This assumes that the daylight integration will
be thoughtfully designed to avoid glare and overheating. In the end, to achieve high quality
lighting and produce energy savings, daylighting and electric lighting systems must be
designed together so they complement each other. Lighting controls are a major area of
integration for these two sources of illumination.
Call Greg Amato at Bay Screens and Shades for more information or an analysis or your building.