Effects Of Sunlight On Human Thermal Perception,Lighting Perception And Physiological Parameters

Indoor environmental quality(IEQ)factors affect the comfort,health and well-being of occupants.Existing research divides indoor environmental quality factors into indoor air quality,thermal environment,light,acoustic,office and layout,biophilia and views,look and feel,location and amenities,etc.The presence of sunlight has an important impact on the indoor thermal environment and lighting environment.At present,for sunny conditions,few studies explore the effects of direct solar radiation on human thermal perception,lighting perception and physiological parameters.As for cloudy conditions,there are few studies to explore the effects of daylight and natural view on thermal perception,lighting perception and physiological parameters.Therefore,it is particularly important to explore the effects of sunlight on human thermal perception,lighting perception and physiological parameters under different conditions.In this paper,the effects of sunlight on human thermal perception,lighting perception and physiological parameters are explored through the methods of climate chamber experiments and field investigations.The main research work is as follows:(1)The effects of direct solar radiation on human thermal perception,lighting perception and physiological parameters were explored by climate chamber experiments.Sixteen subjects were exposed to spaces with and without direct solar radiation,and the irradiated part was on their leg and feet.The ambient temperatures were set at 17℃ and 23℃(representing cool and neutral thermal conditions,respectively).The measured parameters include environmental parameters,physiological parameters(i.e.,skin temperature,blood pressure,oxygen saturation,heart rate variability),and subjective questionnaires(i.e.,thermal perception,lighting perception,emotion,sick building syndrome).The results showed that local direct solar radiation could improve subjects’thermal sensation in a cold environment(0.86thermal sensation vote),with a heating effect equivalent to 2.61℃.Local direct solar radiation could significantly improve subjects’local thermal sensation near the irradiated part,and other parts without direct solar radiation(e.g.,hands,arms)also had some improvements in thermal sensation.Local direct solar radiation could improve the skin temperature of the irradiated area,average skin temperature and some parts without direct solar radiation in a cold environment.Subjects with direct solar radiation had higher lighting perceptions,and rational use of sunlight would have energy-saving potential.Moreover,direct solar radiation had a positive influence on occupants’health,RMSSD increases,indicating that the level of fatigue was reduced.The existence of direct solar radiation could have a positive effect on workers’emotions.(2)The effects of daylight and natural view on human thermal perception,lighting perception and physiological parameters were explored by climate chamber experiments.Twenty subjects participated in the experiment in spaces with and without windows(with daylight and natural view,abbreviation:visual window),and the ambient temperatures were set at 17℃,20℃,and 23℃,representing cool,slightly cool and neutral thermal conditions,respectively.Measurement parameters included environmental parameters,physiological parameters(i.e.,skin temperature,blood oxygen saturation,heart rate variability),and subjective questionnaires(i.e.,thermal perception,lighting perception,emotion,sick building syndrome).Results showed that subjects with visual windows felt more comfortable in a cool environment(0.44thermal comfort vote).Additionally,blood oxygen saturation increased,indicating reduced sick building syndrome symptoms,while the time-domain measurements of HRV increased,indicating stress and fatigue were reduced.Daylight had energy-saving potential(82%in this experiment).The visual window improved the occupants’tolerance to the thermal environment,which will have energy-saving potentials of about 1.21℃ setpoint adjustments of HVAC.(3)Based on the above research results,the effects of sunlight on the thermal perception and lighting perception of the actual office building were explored by field investigations.Divided into sunny and cloudy conditions,a comprehensive questionnaire survey was carried out on the thermal perception,lighting perception,adaptive behavior and work performance of office workers.At the same time,the indoor environmental parameters(i.e.,air temperature and humidity,air speed,black bulb temperature,desk illuminance)were measured,and the use of shading facilities were investigated.A total of 397 questionnaires were collected in this experiment.The results showed that sunlight had a significant impact on the indoor thermal environment.The neutral temperature under sunny and cloudy conditions was 19.8℃ and 21.5℃,respectively,and the sunlight reduced the neutral temperature by 1.7℃.Sunlight could greatly improve the lighting environment near the window area of office buildings,and workers have a higher demand for daylight.The office workers in the window area had a higher self-assessment of work performance.PMV model is not suitable for evaluating the occupants’thermal sensation under solar radiation,while the CPMV~*model is more adaptive.This paper divides sunlight into direct and diffuse parts,and innovatively explores the effect of direct solar radiation on human thermal perception,lighting perception and health,as well as the daylight and natural view on human thermal perception,lighting perception and health.The energy-saving potential of sunlight on HVAC system and lighting system were further analyzed.In addition,through the field investigations,the effects of sunlight on the actual office building thermal environment and lighting environment,as well as the thermal perception and lighting perception of workers are verified.This study aims to improve office building workers’satisfaction and health and will provide theoretical support for the design of office building curtain walls.Moreover,it will provide a basis for improving the evaluation index of human thermal comfort considering solar radiation.