Office workers’ performance and satisfaction with the luminous environment under standard and daylight mimicking LEDs

The effects of illuminance and correlated colour temperature (CCT) on people's work performance, mood, and comfort have been previously investigated, but some aspects need to be deepened. In particular, CCT does not uniquely describe light spectral power distribution (SPD), hence it is not sufficient to define the effects of light on people's non-visual responses. This study aims to extend current knowledge about the acute effects of light on people's work performance, mood, and environmental appraisal by carrying out a 2x2 mixed design experiment where LEDs' SPD (standard and daylight-mimicking) is the within-subject factor and CCT (4000 K and 6500 K) is the between-subject factor. 40 participants, aged between 18 and 35, joined the experiment. It was found that SPD has significant effects on reaction time in selective attention and errors in working memory activities, being the performances under daylight-mimicking LEDs the best. Moreover, a lower number of errors in sustained attention and executive function was registered under 4000 K against 6500 K, but better performances occurred under 6500 K against 4000 K considering errors in selective attention and reaction speed in sustained attention. Regarding room appraisal, 4000 K was preferred over 6500 K and daylight-mimicking LEDs were preferred over the standard ones. • Light effects on office work performance and room appraisal are assessed with tests. • A mixed design study compares LEDs with different spectra and CCTs (4000 K, 6500 K). • In working memory task, number of errors is lower under daylight-mimicking LED. • In selective attention task, reactions are faster under daylight-mimicking LED. • 4000 K CCT and daylight-mimicking spectrum are preferred (significance not reached).