A roof window configured to be installed in a roof structure of a building with a roof arranged with a roof pitch which is larger than 17°, wherein the roof window comprises a sash and a fixation frame, wherein the sash is connected to the fixation frame by means of a hinge arrangement (5, AX2) allowing the sash to be moved relative to the fixation frame between a closed sash position and an open sash position, wherein the sash is a top hung sash and comprises side members (8a, 8b), a top member and a bottom member which together encircles a sash opening, and wherein an insulated glass unit is installed in and connected to the sash, wherein the insulated glass unit comprises a first glass sheet (4a-1) comprising an inwardly facing major surface for facing the interior of the building and a second glass sheet (4b-1) comprising an outwardly facing major surface for facing away from the interior of the building, and wherein the insulating glass unit comprises an inert gas or vacuum in a sealed insulating space between the glass sheets (4a-1, 4b-1), wherein the top hung sash moreover comprises an outer weather shield, which is transparent to at least visible light and comprises an interior major surface and an exterior major surface, wherein the outer weather shield covers the sash opening and wherein an air gap is provided between the interior major surface of the weather shield and the outwardly facing major surface of the insulated glass unit, and wherein the outer weather shield is attached to the sash so as to move together with the sash and the insulated glass unit when the sash is moved between the closed sash position and the open sash position, characterized in that the roof window comprises a lifting system, wherein a first part of the lifting system comprising one or more springs which in the closed sash position extends along a longitudinal frame member (3a, 3b, 3c) of the fixation frame, wherein a lifting force provided by the one or more springs is/are configured to be transferred to the sash when the sash is moved from the closed sash position towards the open sash position, wherein the weather shield extends over and covers elongated parts (3a, 3b, 3c) of the fixation frame, and substantially covers the lifting system, at least when the sash is arranged in the closed sash position, wherein the one or more springs of the lifting system is/are arranged at a location above a first insulated glass unit plane (Pa) defined by the inwardly facing major surface of the insulated glass unit when the sash is in the closed sash position. wherein the sash is a top hung sash and comprises side members (8a, 8b), a top member and a bottom member which together encircles a sash opening, and wherein an insulated glass unit is installed in and connected to the sash, wherein the insulated glass unit comprises a first glass sheet (4a-1) comprising an inwardly facing major surface for facing the interior of the building and a second glass sheet (4b-1) comprising an outwardly facing major surface for facing away from the interior of the building, and wherein the insulating glass unit comprises an inert gas or vacuum in a sealed insulating space between the glass sheets (4a-1, 4b-1), wherein the top hung sash moreover comprises an outer weather shield, which is transparent to at least visible light and comprises an interior major surface and an exterior major surface, wherein the outer weather shield covers the sash opening and wherein an air gap is provided between the interior major surface of the weather shield and the outwardly facing major surface of the insulated glass unit, and wherein the outer weather shield is attached to the sash so as to move together with the sash and the insulated glass unit when the sash is moved between the closed sash position and the open sash position, characterized in that the roof window comprises a lifting system, wherein a first part of the lifting system comprising one or more springs which in the closed sash position extends along a longitudinal frame member (3a, 3b, 3c) of the fixation frame, wherein a lifting force provided by the one or more springs is/are configured to be transferred to the sash when the sash is moved from the closed sash position towards the open sash position, wherein the weather shield extends over and covers elongated parts (3a, 3b, 3c) of the fixation frame, and substantially covers the lifting system, at least when the sash is arranged in the closed sash position, wherein the one or more springs of the lifting system is/are arranged at a location above a first insulated glass unit plane (Pa) defined by the inwardly facing major surface of the insulated glass unit when the sash is in the closed sash position.