ENERGY EFFICIENT LIGHTING
The Approved Document Part L: Conservation of Fuel and Power' has four parts:
Parts L1A and L1B relate to dwellings
Parts L2B and L2B, relate to 'buildings other than dwellings'
The 'A' refers to new buildings and the 'B' to existing buildings.
The documents require that energy used for lighting is restricted
Part L1 (Dwellings) Design Standards for lighting.
1) The luminous efficacy of a low energy lamp is to be 45 lamp lumens/circuit
Watt.
2) The standards require three luminaires out of four (75%) to be fitted with lowenergy lamps - but these can be any type of low-energy lamp provided their
luminous efficacy meets the 45 lm/W requirement. Luminaires can be fitted
with conventional lampholders (Edison Screw or Bayonet Cap)
3) There is an exemption for any luminaire that has a power requirement of less
than 5 circuit Watts – (mostly LED fixtures, and these a low output lighting
and are unlikely to be useful for general area lighting).
4) External lighting - A lamp capacity should not be more than 100 lamp-Watts
and that they should be automatically controlled to switch off when not
required (such as operation by a movement sensor) and fitted with a daylight
sensor.
Part L2 (other than dwellings)Design Standards for lighting
1) General lighting for offices, industrial and storage areas now requires
luminaires to have an initial efficacy of 55 luminaire lumens /circuit Watt.
2) General lighting in other non-domestic spaces will require light sources to
have an average initial efficacy of 55 lamp lumens / circuit Watt.
3) Display lighting requires an initial efficacy of 22 lamp lumens / circuit Watt.
The lighting to be switched off when people are inspecting exhibits or
merchandise or being entertained'
4) Minimum lighting control requiring a light switch by the door to a small room,
or a fully-managed system using time-based or processor-based controls for
larger areas.
FREQUENTLY ASKED QUESTIONS
FAQ 1: How is 'low energy lighting' defined
Every electric lamp consumes an amount of electrical energy in delivering its
illumination. The performance parameters of Part L determine that, to all intents and
purposes, low energy lighting relates to fluorescent sources, high pressure discharge
lamps and some LEDs.
No filament lamps meet the parameters and neither does any luminaire that can be
fitted with a filament lamp - so luminaires have to be dedicated to a low energy light
source.
FAQ 2: what does 'luminous efficacy' mean?
Every lamp delivers a quantifiable amount of light - measured in lumens. Of course,
that light also requires a certain amount of electrical energy to deliver it. Dividing the
one by the other gives us a comparable figure of light generated per “circuit Watt”.
FAQ 3: What are 'circuit Watts'?
Most low energy light sources need some form of electronic circuitry - the control
gear. Every piece of control gear uses a small amount of electrical energy just to
function, so the important figure here is the combined power figure of Lamp Watts +
Control gear Watts = Circuit Watts.
FAQ 4: what is 'luminaire efficacy'?
As soon as you put a lamp into a light fixture, some light is lost within the body of the
luminaire. The difference between the amount of light coming from a naked lamp and
the light coming from the luminaire housing the lamp is known as the Light Output
Ratio, and that defines the luminaire efficacy. Some fixtures can be startlingly
inefficient.
FAQ 5: Does a lamp deteriorate over time
The light output from a lamp deteriorates with age. A new lamp is considerably
brighter than a lamp that's been burning for a few thousand hours.
Part L2 (para.53) calls for the initial lamp lumens (at 100 hours burning) to be taken
into account.