Part L sets the energy efficiency standards required by the Building Regulations. It controls:
- The insulation values of building elements
- The allowable area of windows, doors and other openings
- Air permeability of the building
- The heating efficiency of boilers
- 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 limitations of openings of the building fabric.
Part L also considers:
- Solar heating and heat gains to buildings
- 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
- Requirements for energy metres
Building Regulations are administered separately in England, Scotland and Wales.