A skylight window for being installed in a roof of a building, the skylight window comprising: a window frame having four frame side members, an insulating glazing unit IGU having multiple layers of glazing, and a window sash having four sash side members supporting the IGU, the IGU having an exposed interior major surface for facing an interior of the building in a closed position of the skylight window, the exposed interior major surface being of an interior pane layer of the IGU, said interior pane layer having a periphery and a first peripheral side, a first of the frame side members being associated with a first of the sash side members, said first frame and sash side members (10, 14) extending in a respective longitudinal direction substantially in parallel with the first peripheral side of the interior pane layer, in a closed position of the skylight window, a height direction being defined as extending perpendicularly to the interior major surface of the IGU in the closed position of the skylight window, an outward direction and an inward direction extending from the first peripheral side in opposite directions, the outward direction extending away from the IGU perpendicularly to both the longitudinal direction and the height direction and, the inward direction being opposite to the outward direction, the first sash side member comprising a supporting leg, the supporting leg extending below and supporting the exposed interior major surface of the IGU, the first frame member comprising a primary leg and a secondary leg, where, in the closed position of the skylight window, the primary leg is positioned outwards in relation to the first peripheral side of the interior pane layer and extends in the height direction, the secondary leg extending in the inward direction below a part of said interior major surface of the IGU, first frame side member comprising a cover leg, where, in the closed position of the skylight window, the cover leg is positioned inwards in relation to the first peripheral side of the interior pane layer opposite to the primary leg, and the cover leg extends from the secondary leg in the height direction towards the interior major surface of the IGU, wherein the primary leg extends above the interior major surface of the IGU in the height direction, in the closed position of the skylight window, and a frame spacing is delimited by the primary leg in the outward direction, the cover leg in the inward direction and the secondary leg toward the interior, characterized in that said frame spacing accommodates the supporting leg of the first sash side member in the closed position of the skylight window. a window frame having four frame side members, an insulating glazing unit IGU having multiple layers of glazing, and a window sash having four sash side members supporting the IGU, the IGU having an exposed interior major surface for facing an interior of the building in a closed position of the skylight window, the exposed interior major surface being of an interior pane layer of the IGU, said interior pane layer having a periphery and a first peripheral side, a first of the frame side members being associated with a first of the sash side members, said first frame and sash side members (10, 14) extending in a respective longitudinal direction substantially in parallel with the first peripheral side of the interior pane layer, in a closed position of the skylight window, a height direction being defined as extending perpendicularly to the interior major surface of the IGU in the closed position of the skylight window, an outward direction and an inward direction extending from the first peripheral side in opposite directions, the outward direction extending away from the IGU perpendicularly to both the longitudinal direction and the height direction and, the inward direction being opposite to the outward direction, the first sash side member comprising a supporting leg, the supporting leg extending below and supporting the exposed interior major surface of the IGU, the first frame member comprising a primary leg and a secondary leg, where, in the closed position of the skylight window, the primary leg is positioned outwards in relation to the first peripheral side of the interior pane layer and extends in the height direction, the secondary leg extending in the inward direction below a part of said interior major surface of the IGU, first frame side member comprising a cover leg, where, in the closed position of the skylight window, the cover leg is positioned inwards in relation to the first peripheral side of the interior pane layer opposite to the primary leg, and the cover leg extends from the secondary leg in the height direction towards the interior major surface of the IGU, wherein the primary leg extends above the interior major surface of the IGU in the height direction, in the closed position of the skylight window, and a frame spacing is delimited by the primary leg in the outward direction, the cover leg in the inward direction and the secondary leg toward the interior, characterized in that said frame spacing accommodates the supporting leg of the first sash side member in the closed position of the skylight window.