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Meeting the GLA’s Part L 21, energy efficiency requirement is especially tough for offices and retail units. The required changes will impact architecture and how they are serviced. Developments with high hot water uses, such as leisure facilities or care homes, will have to further consider new technologies to reduce energy used for hot water generation.

Our early assessment has highlighted that the following should be considered to help achieve GLA targets for commercial buildings:

Building design

  • Smaller or darker glazing (i.e., with low g values).
  • Lower air test results will be required, even for small shell units.
  • Building fabric will need to enable U values that match or better requirements for residential elements.


  • Lighting designs need to be optimised and use ultra-efficient LED luminaires (>130 lm/W).
  • Lightings controls are mandatory, with daylight dimming in glazed perimeters and occupancy sensing elsewhere.
  • Ventilation systems need to be even more efficient which means greater plant footprints and greater ductwork dimensions.
  • Wastewater heat recovery must be considered where showers are provided.
  • Heating and hot water will have to be provided by efficient heat pumps.

Connection to heat networks

  • Small units still have some exemptions from connecting to heat network.