What are the different levels of Non-Domestic EPC and why do they matter?

If you own or manage a non-domestic building, you’ll almost certainly come across the need for a Non-Domestic Energy Performance Certificate (EPC). What many building owners don’t realise is that not all Non-Domestic EPCs are the same. They are divided into different “levels”, depending on the size of the building and the complexity of its heating, ventilation and air conditioning (HVAC) systems. Understanding these levels can help you choose the right type of assessment, appoint a suitably qualified energy assessor and, ultimately, get recommendations that are realistic and useful for your particular building.

The different EPC levels for non-domestic buildings

Non-domestic EPCs are split into levels primarily based on the complexity of the building and its building services, especially the HVAC systems. Levels 3 and 4 are both assessed using the Simplified Building Energy Model (SBEM), but the types of buildings they cover are quite different.

Level 3 – Simple buildings

Level 3 applies to smaller, straightforward buildings with simple services. These are often small commercial units, for example a small shop, cafe or office. They tend to be naturally ventilated and heated using simple systems, and are typically under 250 m² in size. At this level, the systems involved are common and relatively easy to model, and there is no requirement for the assessor to demonstrate competence in assessing new-build properties.

Level 4 – Medium complexity buildings

Level 4 still uses simplified methods, but covers buildings that are larger or where the HVAC and controls are more sophisticated. This includes buildings with mechanical ventilation, comfort cooling or full air conditioning systems, such as larger offices, retail outlets and warehouses. Because the building services are more complex, the assessor needs a higher level of competence and training to be able to model them accurately and interpret the results.

Level 5 – Complex buildings

Level 5 covers the most complex or innovative non-domestic buildings – those with advanced or unconventional design features. These might include buildings with atria, automatic shading systems, extensive use of thermal mass, or highly glazed facades such as modern glass skyscrapers. Airports and large shopping centres are typical examples.

Due to the complexity and interaction of the building fabric and services, these properties cannot be modelled reliably using simplified methods. Instead, they must be assessed using Dynamic Simulation Modelling (DSM) software. Level 5 assessors are specifically trained and approved to use this type of software.

Why do these differences matter to building owners?

As a building owner, you don’t need to become an energy modelling expert, but it is important to make sure that your property is assessed at the correct level. Choosing an assessor with the appropriate level of qualification helps ensure that the EPC rating genuinely reflects how the building has been constructed and how its systems operate. When the input is accurate and the method is appropriate, the recommendations you receive are much more likely to be realistic and tailored to your situation.

This has several practical benefits. It supports compliance with regulations when you are selling, renting or refinancing the property. It also helps you plan improvements in a structured way, focusing on measures that deliver real savings in energy use and carbon emissions, rather than generic advice that may not suit your building.

Working with an Elmhurst approved energy assessor

An Elmhurst-approved energy assessor will review your building’s size, use and services; and then model the performance using the appropriate software. They will then provide the EPC and a recommendation report that explains where the building is performing well and where there is room for improvement.  An experienced assessor will talk you through the recommendations in the report so you can better understand their practicality, potential costs and likely impact.