Being　healthy　and　energy　saving　have　become　two　important　principles　of　building　development.　Daylight　is　an　influential　factor　with　the　characteristics　of　both　photometry　and　radiometry.　Irradiance　brings　solar　heat　gains　that　transfer　to　building　cooling　load,　while　illuminance　provides　a　luminous　environment　and　affects　artificial　lighting　system　at　the　same　time.　To　balance　the　energy　and　daylighting　performances,　it　is　reasonable　to　minimize　the　environmental　load　under　moderate　comfort　conditions.　This　study　first　quantified　luminous　comfort　with　a　dynamic　daylighting　metric,　average　daylight　autonomy　(Ave.　DA(300)),　from　a　questionnaire　survey　and　simulation　work.　The　benchmark　of　this　metric　should　range　from　29.6%　to　57.8%　for　high-rise　residential　buildings.　With　this　guideline,　the　Hong　Kong　public　housing　units　is　found　that　part　of　units　lack　of　daylight　due　to　the　high　building　floor　and　density,　while　some　units　have　potential　to　save　energy　by　compromising　daylighting　performance.　Therefore,　a　new　index,　energy　daylight　rate　(EDR),　is　proposed　to　help　decide　the　best　scenario　of　envelope　design　for　both　daylighting　and　shading　purposes.　The　results　show　that　opening　a　secondary　window　is　an　efficient　way　to　bring　more　light　in　and　lengthening　overhang　is　an　efficient　way　to　block　excessive　sunlight.　This　method　and　the　new　index　are　proved　to　have　the　ability　to　help　defining　proper　building　envelope　design　at　the　early　stage.