UK BR Part L2 Compliance: Points of note for Commercial Energy Assessors and building designers

This covers the effects of changes to Part L2 of the UK Building Regulations on the 2010 National Calculation Method and the SBEM 2010 interface.

2010 National Calculation Method (NCM) and Simplified Building Energy Model (SBEM)

 The NCM is used to determine the actual building’s Building Efficiency Rating (BER) and the Target Efficiency Rating (TER) based on a Notional Building. Key changes include:

  •  New NCM Modelling Guide (2010 Edition) supported by the Non-Domestic Building Services Compliance Guide.
  • Revisions to Part L2 come into force from 1st October 2010 requiring compliance to be assessed using SBEM v. 4for new build. EPCs to be assessed using v.4 from 17 April 2011.
  • Aggregate 25% CO2 emission improvement to BER required. Varies with building type and use:
    • Shallow plan (heated only)     22%
    • Shallow plan (air-con)             40%
    • Deep plan (air-con)                 26%
    • Warehouse                              34%
    • Hotel                                       16%
    • School                                     27%
    • Supermarket                            26%
    • Retail                                       21%
  • Reduced number of building uses and activities. Previous 29 uses reduced to 21 ‘use classes’ in line with planning classes.
  • Improved fabric and HVAC system efficiencies and revised opening areas, and new ‘glazing classes’ for Notional Building dependant on ‘use class’.
  • No change to 2006 limiting u-values but significant improvement to Notional Building:
    • Roof                                        0.18
    • Walls                                       0.26
    • Exposed and ground floors    0.22
    • Windows & roof lights           1.8
    • Vehicle access door                1.5 (no change)
    • Pedestrian & high use door     2.2 (no change)
    • Internal wall                            1.8
    • Internal floor/ceiling               1
  • Revised thermal mass parameters.
  • Revised values for non-repeating thermal bridges with option to input QA Accredited Construction details.
  • Revised auxiliary energy calculations
  • Revised heating fuel and heat generator seasonal efficiency procedure for the Notional Building. Heating fuel now the same as the actual building. Therefore no ‘golden bullet’ by using bio-fuel.
  • Now no improvement factor for renewable energy.
  • Heating and cooling demand now aligned with ISO 13790:2008.
  • Night cooling now included as an option.
  • Revised auxiliary energy calculation (e.g. pumps, fans) for Notional and Actual Buildings.
  • Air-permeability of the Notional Building reduced from 10 to 5m3/h/m2 at 50Pa.
  • Demand controlled mechanical ventilation options available.
  • Revised lighting energy procedure and calculation, now 55lm/cw for the notional building.
  • No allowance for occupancy sensors (PIR) for lighting.
  • LED lighting is now a default option for EPC production.
  • The 2010 TER = 2010 Notional Building BER (i.e. not as for the 2002 values being upgraded to 2006).
  • New BR Part L2A Criterion 3 for limiting solar gains. Applies to all buildings with or without air-conditioning.
  • Indoor swimming pool basins added and to achieve u-value no worse than 0.25W/m2.K as calculated according to BS EN ISO 13370.
  • As-designed new build compliance submission to BCB with list of design specifications required. As-built submission required including changes to the designed specification.

SBEM 2010 Interface changes

 In addition to addressing the above some specific SBEM interface changes have been introduced with v4: 

  • New ‘shell & core’ and ‘portable & modular’ assumptions and procedures. Subsequent fit out requires Part L compliance assessment and EPC submission.
  • Bi-valent heating systems are easier to input.
  • Zone parameter length required.
  • More variable speed pump options.
  • Transpired Solar Collectors included as a building feature.

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