RESEARCH OF TIME OF CRITICAL ILLUMINATION TO ASSESS THE DURATION OF DAYTIME ILLUMINATION

Natural lighting of buildings has an important morphofunctional value, since the human body is formed in natural environment. In modern conditions, additional with artificial light sources used a lack lighting, this leads to energy costs. The duration use day depends on many factors, including climate region. paper, authors propose approach preliminary assessment time taking into account differences climate. Calculations illumination open horizontal surface are carried out for three cities Russian Federation (Sochi, Moscow, St. Petersburg) basis actinometric reference data using equivalent solar radiation all months year by daylight hours. calculation uses total clear and cloudy skies hourly accounting probability sunshine. value critical outdoor selected from specialized literature. Based calculated obtained distribution illumination, table end morning begin intermediate evening each city month under consideration compiled. Therefore, Sochi, estimated 4 hours longer than 7 Petersburg. This can be light. Further works will devoted clarifying approach.