New PartL 2021 Regulations - What to Expect

PartL 2021 and net-zero

The new 2021 Part L Regulations will be a major step towards realising the goal of net-zero energy buildings, and achieving this will bring many new challenges and opportunities in nearly all aspects of the building life-cycle, from design to final construction.

Buildings will need to be designed from initial conception with these regulations in mind, and every building construction standard such as those for building fabric, air-tightness and plant efficiency will be integral to achieving the required Energy Usage and Carbon Emission targets.

OpenBuildings Energy Simulator, now contains the related PartL 2021 calculation, and is fully approved by the Energy Performance of Buildings Division.

Certification and Free Training

The related training for PartL has been made available for free to our users, and can be accessed On-Demand via the Bentley LearnServer

Bentley are fully approved as a certification and training partner with CIBSE, and Energy Assessors can become certified via our hassle-free, online PartL exams - exam dates are listed on our Energy Simulation Forum.

What to Expect?

Significant changes from the previous regulations should be expected, due to the new calculation methodology, and new standards being adopted. These include:

Compliance Changes:

The main changes to results can best be seen by inspecting the new BRUKL Compliance Report.

Specific details on this can be found in the following article: 2021 PartL Compliance Changes - OpenBuildings

New calculation checks:

The SBEM calculation now includes workflows to ensure consistent building models and more accuracy. For instance, SBEM will now check that a room’s HVAC type matches that expected by the room’s activity type:

SBEM error - "ZONE defined as conditioned..." - OpenBuildings

Interface Changes:

Changes to the user interface for PartL are minimal, but include:

  • EPBD Recast renamed Regulation 25A
  • New Part L 2021 Room Mapping options, in order to incorporate new room types – 2021 PartL Room Types - OpenBuildings
  • New HVAC System type for Chilled Ceilings:

Calculation methodology:

Many of the changes will not be visible in the PartL software interface directly, but will background data used by the SBEM calculation. These are as defined in the 2021 National Calculation Methodology.

The underlying changes are available to view in the NCM Modelling Guide, available from: NCM_Modelling_Guide_2021_Edition_England (