A conservation area is an area of specific architectural or historical interest, the character or appearance of which is desirable to preserve or enhance. Many of your towns, local street scapes rely on historic windows for much of their architectural impact and character. Inappropriate, poor quality replacement windows can easily erode traditional features on historic buildings. Homeowners should always seek appropriate consent if they live in a conservation area.
Article 4 is when a planning authority applies to restrict development rights in a conservation area. Replacement windows then need planning approval and conservation area consent. This is quite rightly done to preserve architectural merit. Some planning authorities precluded the use of modern materials because the window designs were inappropriate in size, shape and design. A more modern approach has been to approve the use of Residence 9 because of its consideration of the Article 4 directives. It has been specifically designed to replicate the documented historical window designs from the period.
Listed buildings are the most important buildings in the town and are protected nationally with specific control over alterations. It is generally more difficult to replace windows in these buildings and approval must be obtained via English Heritage or Historic Scotland.