Energy impact of integrative lighting: a systematic literature review

Integrative lighting promoting circadian health has recently gained attention due to the increasing awareness of non-visual effects of light and advancements in lighting technology. However, reaching both visual and non-visual circadian targets in buildings may be challenging when considering energy use. Despite growing interest, most studies have focused on health benefits and individual design parameters, leaving the energy implications of integrative lighting insufficiently explored. This systematic literature review investigates the energy impact of implementing non-visual lighting requirements in buildings, with a specific focus on daily active occupants. The review identifies four factors affecting energy use: light quantity, light spectrum, spatial pattern, and timing. Although the energy impacts of integrative lighting have not been thoroughly investigated by literature, the findings suggest that light quantity is the primary factor affecting energy use. Reliance on electric lighting for non-visual targets can result in up to a 300% increase in energy use compared to lighting systems addressing visual targets only. The results also show that a greater emphasis on daylight utilization reduces the dependence on electric lighting, while meeting non-visual needs. Additionally, well-designed spatial patterns and appropriate adjustments in spectral power distribution can potentially improve energy efficiency of integrative lighting systems, hence lowering energy use. As overarching recommendations, this article advocates for greater integration of daylight into integrative lighting schemes, and for a general re-thinking of light distribution from electric lighting fixtures.