Common menu bar links
CONSTRUCTION INNOVATION, Summer 1998
[ Table of contents | Subscribe ]
Daylighting research in atriums indicates potential for significant energy savings
IRC's research into the effects of natural light, or daylighting, in atriums has the potential to significantly increase energy savings, assisting building owners, managers and occupants as well as building designers.
Daylighting is a source of light that can be used as an alternative to electric lighting, thereby reducing energy consumption.
Two atriums were the focus of the work, which formed part of an ongoing IRC-led consortium research project on atrium design. One atrium featured an on/off electric lighting control system, while the other had a continuous dimming system. The studies used field monitoring and computer modelling to evaluate:
- the daylight contribution to the atrium floor and adjacent spaces
- the associated electrical energy savings
- the performance of the daylight-linked electric lighting systems.
The results will be used to recommend improvements to the daylighting performance of atrium buildings.
In the atrium with an on/off automatic lighting system, monitoring results showed a high daylight contribution at the atrium perimeter at each of its three floor levels, in both winter and summer. However, this contribution decreased on both the ground and second floors as distance from the perimeter increased. Only on the third floor was the daylight contribution into the adjacent spaces significant all year round.
While the existing daylight-linked on/off control performed relatively well in summer, it performed very poorly during the winter because of the location of the control photocell under a skylight covered by heavy snow or frost. In addition, the installed lighting power density for this atrium was found to be substantially higher than that recommended by current lighting standards.
DAYLIGHT IN A SECOND FLOOR CONFERENCE CENTRE IN THE ATRIUM
IRC recommended improving the existing lighting system's energy savings by relocating the photocell, or at least clearing the skylight, and reducing the installed lighting power density.
Data analysis and computer simulations suggest that replacing the on/off system with a dimming system would increase savings even further.
INDOOR AND OUTDOOR VIEWS OF ATRIUM SKYLIGHT
In the atrium with the continuous dimming system, the results indicated that, except for some areas on the second and third floor walkways of this five-floor atrium, the illuminance from daylighting alone was not high enough to meet accepted lighting criteria for a significant period of time during the day.
This suggests that an on/off automatic lighting control system would have been an impractical solution, and that the installed continuous dimming system is an appropriate lighting control strategy for achieving energy efficiency.
However, the researchers found that the dimming system did not perform according to the manufacturer's claims and that the adjustment of the lighting system's electrical phases was incorrect.
Field measurements and calculations show that these problems, if corrected, would increase the dimming system's energy savings - now estimated at 46 percent annually (or $6,550) - to 73 percent.
IRC's work in obtaining field data on the contribution of daylighting to energy savings and in evaluating computer models for buildings with atriums provides a firm basis for energy conservation strategies. Results from this research, in the form of design guidelines for the selection of skylights, will help building designers optimize the potential of daylighting, both as a source of lighting, and as a means of saving energy and money.
