Contractors have been approached to provide costings for a rear extension in Plymouth. The project involves demolition of an existing conservatory and its replacement with an extension of more solid construction. The back of the existing house will be opened up to access the new space. Generally speaking, the allowance for glazing in these kind of projects is 25% of the new floor area. Crayon has experience of gaining consent for larger areas of glazing when the application is supported by SAP calculations. We are able to justify highly glazed areas by adding extra insulation in the walls, floor and roof – thus balancing potential heat losses through windows and doors.