FENSA stands for the Fenestration Self-Assessment Scheme. It has been set up by the Glass and Glazing Federation (GGF) and other industry bodies with Government encouragement in response to the current Building Regulations for England and Wales.

When having windows and doors replaced homeowners must comply with current thermal peformance standards and ensure that they get a certificate of compliance from FENSA or from Local Authority Building Control. FENSA also enables companies that install replacement windows and doors to self certify compliance under these Building Regulations. (This information is taken from the official FENSA website)