Most commercial EPCs are produced with SBEM, the Government's simplified calculation tool. For the most complex buildings, a Level 5 EPC is required, and that means Dynamic Simulation Modelling (DSM) using approved software. DesignBuilder, built on the EnergyPlus simulation engine, is one of the most widely used approved DSM tools in the UK.
This guide explains what makes a building Level 5, how DesignBuilder produces the EPC, and what owners should prepare.
What makes a building Level 5?
EPC assessor levels reflect building complexity. Level 3 covers simple buildings, Level 4 most commercial buildings with typical HVAC, and Level 5 the most complex: buildings with features such as atriums, displacement ventilation, chilled beams, complex mixed-mode ventilation or unusual geometry that SBEM cannot represent well.
Only an accredited Level 5 assessor using approved DSM software can lodge a Level 5 EPC.
How DesignBuilder produces the EPC
The assessor builds a 3D model of the building from drawings and survey data, then assigns constructions, glazing, zones and activities using the National Calculation Methodology (NCM) database.
HVAC systems, lighting and controls are modelled in detail. The simulation runs hour by hour across a full weather year, and the results are compared with a notional building to calculate the rating. The EPC is then lodged on the national register.
Why DSM often gives a fairer rating
SBEM uses simplified, monthly calculations and conservative defaults. For buildings with atriums, glazed cores or advanced ventilation, those defaults can understate real performance.
DSM models how heat, light and air actually move through the building. Where the design is genuinely efficient, that usually shows in the result. It must reflect the real building: DSM is a more accurate tool, not a way to inflate a rating.
What you need to provide
Up-to-date floor plans, sections and elevations; specifications for fabric and glazing; HVAC schematics and plant data; lighting layouts and controls information; and O&M manuals where available.
Better evidence means fewer default assumptions, and fewer defaults usually means a more accurate rating. See our DSM modelling checklist.
Next steps
If your building has complex features and a borderline rating, a DSM review can show whether a Level 5 assessment is appropriate. Talk to us or read about our commercial EPC service.
General guidance only; assessor accreditation and approved software requirements are set by the relevant schemes and Government.
Frequently asked questions
- What is a Level 5 EPC?
- A non-domestic EPC for the most complex buildings, which must be produced by an accredited Level 5 assessor using approved Dynamic Simulation Modelling software.
- Is DesignBuilder approved for EPCs?
- DesignBuilder is a widely used approved DSM software for non-domestic EPCs and Part L calculations in the UK. Assessors should check the current approved software list for the version used.
- Is a Level 5 EPC more expensive?
- Usually, because building a detailed simulation model takes longer. For complex buildings, the more accurate result can be worth far more than the fee difference.
- Can DSM improve my EPC rating?
- Where SBEM defaults understate real performance, DSM can give a more accurate and often better rating. It must reflect the building as it is.