An outwardly opening window assembly, comprising a window frame, a window sash comprising four linear profile members where at least one of said linear profile members is pivotably attached to said window frame, a window pane supported by said window sash and a locking mechanism located along at least one profile member of the sash and arranged to lock the window sash in position with respect to the window frame when said locking mechanism is engaged, each of the four linear profile members comprising: an outer element which comprises: a surface which is in contact with a portion of the outer surface of the window pane, a flange which extends at least partially opposite a peripheral edge of the window pane and means for attaching mounting hardware to said outer element, a thermally resistive element which is connected to said flange of said outer element, and an inner element which is connected to said thermally resistive element and which comprises a surface which is in contact with a portion of the inside surface of the window pane, the locking mechanism being located closer to the inside of the window assembly than the innermost portion of the flange of the outer element of the profile member of the sash along which the locking mechanism is located, characterized in that the window assembly further comprises at least one re-enforcement fitting which is fastened to the outer element of one of the linear profile members of the window sash and which, in a closed position of the window assembly, extends away from the plane of the window pane in a direction towards the inside of the window assembly such that at least a portion of said fitting is located between at least a portion of the inner element which is connected to said thermally resistive element and a portion of the window frame, and in that the re-enforcement fitting is in supporting contact with a portion of the locking mechanism. a surface which is in contact with a portion of the outer surface of the window pane, a flange which extends at least partially opposite a peripheral edge of the window pane and means for attaching mounting hardware to said outer element, a thermally resistive element which is connected to said flange of said outer element, and an inner element which is connected to said thermally resistive element and which comprises a surface which is in contact with a portion of the inside surface of the window pane, the locking mechanism being located closer to the inside of the window assembly than the innermost portion of the flange of the outer element of the profile member of the sash along which the locking mechanism is located, characterized in that the window assembly further comprises at least one re-enforcement fitting which is fastened to the outer element of one of the linear profile members of the window sash and which, in a closed position of the window assembly, extends away from the plane of the window pane in a direction towards the inside of the window assembly such that at least a portion of said fitting is located between at least a portion of the inner element which is connected to said thermally resistive element and a portion of the window frame, and in that the re-enforcement fitting is in supporting contact with a portion of the locking mechanism.