Part L of Building Regulations (Conservation of Fuel & Power)
Part L sets the energy efficiency standards required by Building Regulations. It controls the insulation values of building elements, the allowable area of windows, doors and other openings, air permeability of the structure, the heating efficiency of boilers and the insulation and controls for heating appliances and systems together with hot water storage and lighting efficiency. It also sets out the requirements for SAP (Standard Assessment Procedure) calculations and Carbon Emission Targets for dwellings.
In addition to insulation requirements and limitation of openings of the building fabric, the part also considers solar heating and heat gains to structures, it controls heating, mechanical ventilation and air conditioning systems, lighting efficiency, space heating controls, air permeability, solar emission, the certification, testing and commissioning of heating and ventilation systems, and requirements for energy meters.
Building regulations are administered separately in England, Scotland and Wales.