Circadian Characteristics of Special Glazing

The window provides the natural daylight for the indoor environment. Recent discoveries in photobiology found, that light, especially natural daylight not only enables visual performance but has even more effects on the human body. Light properties in a longterm inhabited environment can seriously influence the health state and well-being of occupants. The non-visual effects on the human body are linked to the maintenance of our circadian rhythms, including sleep cycles, metabolism, core temperature and a large number of biological processes in our body. Sick Building Syndrome (SBS) is also a frequented issue. Inappropriate lighting in the indoor environment is assumed to be one of the reasons of sick building syndrome occurrence which is connected to Seasonal Affective Disorders (SAD). The parameters of indoor light climate can be influenced by the selection of window glazing. The presented paper deals with a two way evaluation of spectral characteristics of a selection of special window panes. The scale of samples includes various tinted glasses, low emissivity window panes and other modern window glazing. In the first part, spectral transmittance of the samples is measured with a spectrophotometer. The outputs are classified in terms of their visual and photobiological response. The second part includes measurements, where some of the selected samples are used in our experimental models. One of the models is considered to be the reference model equipped with single clear glass. The internal surfaces of all models are in spectrally neutral colours. All other models have a window equipped with a sample of chosen special glazing. The light conditions used for these longer? term observations are covered by natural daylight. The measuring devices are located in the models so that the visual response and also non-visual impact of light parameters inside the models can be recorded. The experiment demonstrates, that despite very high external illuminance, selected tinted glazing causes filtration of almost one half of the SPD doses in comparison with the reference model with clear glass. The measurements were made in four positions related to the window. This reflected worse results for monitored parameters devoted to non-visual response ? the normalized circadian light CLA and circadian stimulus CS. The measurements were repeated with included external shading obstacles which simulated an adjacent building. The differences were more noticeable for all positions.