Author’s response to JA Love and J Lynes

North American Great Plains, characterized by Robbins1 as a low turbidity region. In Table 1, both ‘overcast’ and ‘cloudy’ conditions are noted. Do these both correspond to the World Meterological Organization (WMO) definition of overcast sky, or are they different conditions? The hours selected for assessing switching and savings are 0830–1700. For many ‘unowned’, ‘managed’ spaces (e.g., circulation areas in retail complexes), times outside this period would be of interest. This is particularly true north of 40° latitude, where significant electrical savings might be made on summer evenings. The lowest light level selected for activating lighting in this analysis was 350 lux. It would have been useful to consider a lower level such as 200 lux, which would satisfy illumination guidelines for spaces for circulation. Another question that arises with respect to the recommended ‘slow dim out’ is, if one has a ballast capable of dimming, why not use a dimming strategy, which would provide a greater reduction in electricity use than any stepped dimming strategy? This study is based on placing control detectors in each controlled space. Given the widespread use of building automation systems, it would seem preferable to use an ‘open loop’ approach for ‘unowned’, ‘managed’ areas and reduced the number photocells to install, calibrate, and maintain. The space-specific responses to instantaneous daylight availability would be determined by control algorithms, eliminating some of the difficulties experienced with closedloop control with ceiling-mounted detectors. If the author has the daylight availability data for the measurement period, it would be interesting to know the relative performance of control based on these data.