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What is Part L ?

In April 2006, Part L was introduced into the Building Regulations to deal with the conservation of energy in new and existing buildings, and both domestic and commercial premises.

The UK Government has a legal commitment to implement the European Directive on Energy Performance in Buildings [EPBD] which requires all new and existing buildings to be given an energy rating and for new buildings to meet a minimum standard of energy efficiency.

This presented a considerable challenge to architects, designers and specifiers and had a significant effect on the UK design and building industry.

The 2006 requirements called for :-

  • 1 in 4 fixed light fittings or 1 fixed light fitting per 25 sq metres to be "energy efficient". 
  • All "energy efficient" fittings to be dedicated types that could only be fitted with compatible energy efficient lamps. Edison screw [ES] and bayonet cap [BC] lampholders could not be used.
  • The definition for "energy efficient" in this case was "in excess of 40 lumens per circuit watt."  

On 1st October 2010 the guidance for Part L1 and Part L2 changes significantly.

The 2010 requirements call for :-

  • For domestic dwellings [Part L1]  3 in 4 or 75% of fixed light fittings are to be "energy efficient".
  • The requirement for "dedicated" types has been relaxed and for the fixed light fittings, edison screw [ES] and bayonet cap [BC] types can now be used.
  • The definition for "energy efficient" has increased to 45 lumens per circuit watt

These requirements exclude garages, cupboards and other storage spaces. Any luminaires with a power requirement of less than 5 circuit watts are also excluded from calculations.

  • For display lighting [ Part L2 - retail, exhibition, entertaining ] the requirement has increased by 50% from 15 lumens per circuit watt to 22 lumens per circuit watt
  • For commercial installations [ Part L2 - offices, industrial, storage ] the requirement has increased by 10% from 45 lumens per circuit watt to 55 lumens per circuit watt.

We understand that contracts signed before 1st October 2010 can comply with the 2006 guidance provided the installation work starts before April 2011. All contracts signed on or after 1st October 2010 must comply with the 2010 guidance.

Lumens per watt  [ lm / W ] is an expression of the amount of electrical energy required  [measured in Watts]  for a given output of light  [measured in Lumens].  

For example, an ordinary incandescent lamp or bulb, uses 100 Watts to produce 1700 lumens compared with a compact fluorescent lamp that uses only 26 Watts to produce 1800 lumens. In other words the same amount of light for 75% less energy.

Examples of fittings that achieve these standards are those using fluorescent tubes, compact fluorescent sources [CFL] and LEDs [Light emitting diodes]. Fittings using discharge lamps such as metal halide, sodium, mercury vapour, also fall into this category but are more commonly used in commercial applications.


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