Rockhill House is a 19th century country house on the banks of the River Swilly on the edge of Letterkenny, Co Donegal. It is one of only two remaining country houses near Letterkenny. Private owners of the house include the Chambers and Stewart families. The house was occupied by Anti-Treaty forces during the Irish Civil War and following independence was used as a teaching college.Rockhill Estate was sold to the Commissioner of Public Works in 1937 and much of the land was sold on to local farmers. It now stands on about 29 acres. With this listed building the glass used in the window restoration was IMC Slim-glaze which offers low sight-line and low U-values while being able to glaze in the traditional look of the original style windows. Starting at 11mm thick these double- glazed units can optimise the insulation provided within the home with a 77% reduction of heat loss compared to the original single glazing which was first used.