ABSTRACT
Introduction: This study investigated the health effects of two different architectural glass types: A two-layered low-iron high transmittance glass and a three-layered low energy glass with lower transmittance. The study investigated how these glass types affected daylight conditions in 72 residential apartments, as well as health and satisfaction of the residents.Methods: The study installed high transmittance glass (light transmittance LT:0.82) in 36 apartments and low transmittance (LT:0.74) in 36 identical apartments. The study then analyzed the light transmittance of each glass type in the laboratory and analyzed the indoor environmental quality (IEQ) in eight representative apartments before and after renovation. Self-reported questionnaires were handed out and collected before and after renovation.Results: The results showed that the glass types differed significantly in measured daylight transmittance. The two-layered high transmittance glass transmitted 15% more visual light (380-750 nm) and 20% more light in the spectral range (460-480 nm), stimulating ipRGCs and circadian rhythm, when compared to three-layered low energy glass. In addition, significant differences were observed in the UV-B spectrum (280-315 nm). While two-layered high transmittance glass transmitted UV-B, three-layered low transmittance glass did not. During the 12-month study period, residents in apartments with three-layered low energy glass reported more difficulties sleeping (p = 0.05), higher satisfaction with daylight (p = 0.03) and higher satisfaction with ventilation (p = 0.04). Residents in apartments with three-layered low energy glass experienced fewer days with too cold indoor temperatures (p = 0.02), compared to residents with two-layered low-iron glass. The results of energy consumption for heating showed that two-layered low-iron glass reduced the energy consumption by 11.0%, while three-layered low energy glass reduced the energy consumption by 9.4%, compared to the year prior to renovation.Conclusion: The results contribute to a discussion about potential energy savings on one hand and potential non-energy benefits, such as daylight quality, overall health, and total economy/life cycle assessment of the built environment on the other hand. The results suggest further research performed in randomized large-scale studies.
Subject(s)
Circadian Rhythm , Sleep , Humans , Self Report , Surveys and Questionnaires , IronABSTRACT
In laser lighting, a major benefit over other lighting techniques is the possibility to achieve very high luminous exitance. Focusing the exciting laser to a very small spot size on the phosphor, however, does not necessarily provide a very small emitting area for the white light. In this study we investigate experimentally and numerically the relationship between the white light spot size and the incident blue laser spot size. We show that the specific phosphor material properties have significant impact on this relationship and on the achievable minimum spot size. This constitutes a limitation on the minimum spot size achievable in laser lighting and has important implications in applications.
ABSTRACT
We report observations of saturation effects in a Ce:LuAG and Eu-doped nitride ceramic phosphor for conversion of blue laser light for white light generation. The luminous flux from the phosphors material increases linearly with the input power until saturation effects limit the conversion. It is shown that the temperature of the phosphor layer influences the saturation power level and the conversion efficiency. It is also shown that the correlated color temperature (CCT), phosphor conversion efficiency and color rendering index (CRI) are dependent both on the incident power and spot size diameter of the illumination. A phosphor conversion efficiency up to 140.8 lm/W with CRI of 89.4 was achieved. The saturation in a ceramic phosphor, when illuminated by high intensity laser diodes, is estimated to play the main role in limiting the available luminance from laser-based lighting systems.
