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.
“The use of modern material will be accepted provided that the window is of design, dimensions, detailing and opening mechanisms are similar to the original window”