Background: Good visual conditions are prerequisites for achieving a good work environment. This intervention study was conducted in connection with an update to modern energy-efficient luminaries with combined indirect plus direct light in 300 offices in a public administrative building. Users' subjective assessment of lighting quality, frequency and severity of visual discomfort, were studied. The changes in illuminance, luminance and contrast balances at a large number of measuring points in the offices compared to visual discomfort. The calculated reduction in energy consumption, which was the basis for investment decisions, was followed by theoretical calculations and practical measurements.
Method: A structured web-based questionnaire on visual ergonomics was sent to 90 participants prior to the intervention (response rate 82 %) and to the remaining 74 participants after the intervention (response rate 88 %). Light measurements were carried out in offices and the energy consumption of luminaries were measured before and after intervention.
Result: Prior to the intervention, i.e. when still using the old luminaries, there was no correlation between the reported prevalence of visual discomfort and visual- and lighting conditions. After the intervention the general impression of lighting had improved. Most users preferred the combination of indirect plus direct light or indirect light only. Visual discomfort and the luminance quotient for all variables improved. No individual correlation between the reduction of visual discomfort and lighting intervention could, however, be demonstrated. The update of luminaries resulted in a decrease in energy consumption with about 32 %.
Conclusion: The results suggests that a update to energy-efficient luminaries can result in a marked reduction of visual discomfort and a significantly improved subjectively and objectively assessed light enviroment. Furthermore, the energy consumption reduced significantly. Thus reduced energy costs and profits of the external environment was not achieved at the expense of deterioration in the working environment.
Keyword: Vision conditions, vision ergonomics, lighting conditions, lighting intervention, eyediscomfort, musculoskeletal disorders, VDT workplaces, luminance, energy.