A skylight window for being installed in or on a flat roof of a building, the skylight window comprising: a window frame having four frame side members and potentially a window sash having four sash side members, the frame side members or the potential sash side members supporting an insulating glazing unit, abbreviated IGU, having multiple layers of glazing, a first of the frame side members and a potential first sash side member extending in a longitudinal direction along a first peripheral side of the IGU, a weather shield comprising a transparent weather shield pane and a weather shield skirt said weather shield pane being surrounded by the weather shield skirt, said skirt extending on an outer side of all four sides of the frame, wherein said weather shield is attached to the frame or to the potential sash so as to protect a window portion of the skylight window, the window portion comprising the frame, IGU and the potential sash, a curb flange having a bottom flange surface, a side flange surface, and an inclined flange surface, said inclined flange surface connecting said bottom and side flange surfaces, wherein the IGU extends in a lateral direction, defining an IGU plane, wherein the curb flange is adapted for extending along a longitudinal extent of a first side frame member in an installed position of the skylight window, said bottom flange surface being positioned for abutment with an outer surface of said roof and said side flange surface being positioned in abutment with said first side frame member, whereby said inclined flange surface is configured for functioning as a roofing felt mounting surface, characterized in that said curb flange is configured for being attached to and detached from the first frame side member, wherein the curb flange may be attached to the first frame side member in different positions in a height direction according to an installation position of the skylight window in the roof, the installation position defining the depth of the skylight window in the roof, the height direction being perpendicular to the lateral direction, and that the inclined flange surface comprises a recess extending in the longitudinal direction of the curb flange, adapted for receiving a countersunk fastener. a window frame having four frame side members and potentially a window sash having four sash side members, the frame side members or the potential sash side members supporting an insulating glazing unit, abbreviated IGU, having multiple layers of glazing, a first of the frame side members and a potential first sash side member extending in a longitudinal direction along a first peripheral side of the IGU, a weather shield comprising a transparent weather shield pane and a weather shield skirt said weather shield pane being surrounded by the weather shield skirt, said skirt extending on an outer side of all four sides of the frame, wherein said weather shield is attached to the frame or to the potential sash so as to protect a window portion of the skylight window, the window portion comprising the frame, IGU and the potential sash, a curb flange having a bottom flange surface, a side flange surface, and an inclined flange surface, said inclined flange surface connecting said bottom and side flange surfaces, wherein the IGU extends in a lateral direction, defining an IGU plane, wherein the curb flange is adapted for extending along a longitudinal extent of a first side frame member in an installed position of the skylight window, said bottom flange surface being positioned for abutment with an outer surface of said roof and said side flange surface being positioned in abutment with said first side frame member, whereby said inclined flange surface is configured for functioning as a roofing felt mounting surface, characterized in that said curb flange is configured for being attached to and detached from the first frame side member, wherein the curb flange may be attached to the first frame side member in different positions in a height direction according to an installation position of the skylight window in the roof, the installation position defining the depth of the skylight window in the roof, the height direction being perpendicular to the lateral direction, and that the inclined flange surface comprises a recess extending in the longitudinal direction of the curb flange, adapted for receiving a countersunk fastener.