TY JOUR TI RESEARCH OF TIME OF CRITICAL ILLUMINATION TO ASSESS THE DURATION OF DAYTIME ILLUMINATION KW day lighting of premises of buildings KW the light equivalent of solar radiation KW artificial lighting KW energy saving KW intermediate light KW critical outdoor natural illumination JO Bulletin of Belgorod State Technological University named after. V. G. Shukhov AU Korkina, E.V. AU Shmarov, I.A. AU Voytovich, E.V. PY 2022 IS 7 PB Belgorod State Technological University named after V.G. Shukhov