FENSA CPS is a government-authorised scheme that monitors Building Regulation compliance for replacement windows and doors.
FENSA Competent Person Scheme (CPS): the self-certification scheme for the Installation of replacement windows, roof lights, roof windows or doors in existing dwellings of under 18m height in England and Wales operated by FENSA Limited.
The window and door replacement activities that are out of scope are:
New porches or existing porches where there is no heating
Loft conversions Property conversions (i.e. a house being split into multiple flats)
Repairs (where frame not included)
Some properties in conservation areas