FENSA is the industry standard for replacement windows and doors. Installers must be self-certified in compliance with any building regulations. FENSA is a brand trusted by all local authorities, industry and government. Having a FENSA installer like Green Double Glazing means that you do not have to register your window or door installation with the local authority yourself. Not only is this approach much faster and easier; it will also save you hundreds of pounds. Furthermore, all FENSA Registered Businesses must give a guarantee or warranty for a period of ten years.
Certass are specialists in installer certification for the building fabric refurbishment industry. Within the building refurbishment market the main area that the Certass licensed scheme falls into is Glazing and Insulation. In addition, they also have a product certification scheme called the Thermal Ratings Register, which ensures the thermal compliance of replacement windows and doors that Green Double Glazing supply and install.