Why are Energy performance Certificates required?
An Energy Performance Certificat (EPC) is intended to inform potential buyers or tenants about the energy performance of a building, so they can consider energy efficincy as part of their investment or business decision to buy or occupy that building.

How long is it valid for?
EPC's for the sale or letting of buildings that are not dwellings are valid for 10 years, or until a newer EPC is produced, if sooner.

What is an EPC and what does it mean?
The EPC looks broadly similar to the energy labels now provided with vehicles and many household appliances. Its purpose is to indicate how energy efficient a building is. The certificate will provide an energy rating from A to G, where A is very efficient and G is the least efficient. The better the rating, the more energy-efficient the building is and lower the fuel bills are likely to be. The energy performance of the building is shown as a Carbon dioxide (CO2) based index.
Each energy rating is based on the characteristics of the building itself and its services (such as heating and lighting). Hence this type of rating is known as an asset rating.
The asset ratings will reflect considerations including the age and condition of the building.
it is accompanied by a recommendation report, which provides recommendations on using the building more effectively, cost effective improvements to the building and other more expensive improvements which could enhance the building's energy performance.

Responsibilties for providing EPC's.
As soon as a building is offered for sale, it is the responsibilty of the seller to make available an EPC to prospective buyers free of charge.
As soon as a building is offered to let, it is the responsibilty of the prospective landlord to make available an EPC to prospective tenants.