How Lighting Affects an EPC Rating


For many buildings, lighting makes the most significant contribution to CO2 emissions and therefore EPC rating. This is particularly true for deep plan offices and shops, where daylight contribution to lighting is typically small and which are therefore predominantly electrically lit.

There are two types of lighting considered within the EPC assessment tools: general lighting and display lighting. For the EPC calculation, general lighting is included in every zone in the building. Display lighting is only included for certain building types and is intended either to provide a feature or to highlight displays of merchandise or exhibits. Display lighting energy may be significant in buildings such as retail units, restaurants, auditoria, dance halls, museums and conference halls. For these building types it is important that high efficacy display lighting is installed and that is reflected in the EPC rating tool. For other types of buildings display lighting is unlikely to make a significant contribution to the rating.

Lighting controls are also a key part of an energy efficient lighting strategy. To minimise energy use, electric lighting should only be used when it is required. When daylight is sufficient, or a room is unoccupied, lighting should be switched off or dimmed. EPC rating tools allow various types of lighting controls to be entered including photoelectric control (daylight linking) and occupancy controls such as feedback from Passive Infra-Red (PIR) sensors.

In order to assess potential savings for an existing building, a lighting survey should be performed in order to identify the existing lamp and luminaire types and lighting controls. Where a lighting system has been identified as inefficient, lighting system upgrades typically have short payback periods and are generally a very cost effective way of improving a building’s EPC rating.

The next step is for a full lighting design to be carried out for each area in the building. Once the upgraded lighting design parameters are known these can be adjusted in the building EPC rating model in order to assess the impact on the EPC rating.

The commercially available lighting types with the highest efficacies are T5 fluorescent tubes and light Emitting Diodes (LEDs). Of these two lighting types good quality LEDs have the longest lifespan and therefore lead to reduced ongoing replacement and maintenance costs. In many cases, depending on application and specification, LEDs will also be more energy efficient and this higher efficacy can be reflected in the EPC rating tool, leading to an improved EPC rating.

The Part L minimum effective lighting efficacy for new lighting installations are 60 luminaire lumens per circuit-watt for general lighting in office storage and industrial spaces for 60 lamp lumens per circuit watt for other types of space. For display lighting a minimum efficacy of 22 lamp lumens per circuit watt is prescribed. However, these are minimum figures, and it should be possible to exceed these values for most building spaces. It should be noted that the default efficacy values (in fact all defaults) within the EPC rating software are generally cautious and therefore it is always better to use an actual value where these can be determined.

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