An engineering sustainability consultant calculates, models and certifies the energy and carbon performance of buildings. For new homes, they produce the SAP calculation required by Part L1A of the Building Regulations; for commercial buildings, they run the SBEM or dynamic energy model for Part L2A compliance. They also carry out BREEAM assessments, Passivhaus design consultancy, overheating analysis to Part O, and embodied carbon assessments - increasingly required by planning authorities as net zero carbon commitments become mainstream in planning policy.
What they do
- SAP calculations for new dwellings (Part L1A compliance)
- Part L energy compliance reports for extensions and commercial buildings
- BREEAM assessments - design stage and post-construction
- Passivhaus design consultancy and certification input
- Overheating assessment to Part O (dynamic thermal modelling)
- Embodied carbon assessment (RIBA 2030 Climate Challenge framework)
- Whole-life carbon and net zero carbon pathway planning
- Energy modelling using IESVE, DesignBuilder or similar software
When you need one
Sustainability consultants are needed whenever Building Regulations require energy compliance calculations, when planning conditions require BREEAM or sustainability appraisals, or when a project is targeting Passivhaus or net zero carbon standards.
Typical costs (UK, 2025)
| Job type | Typical cost |
|---|---|
| SAP calculation (new dwelling) | £300 - £700 |
| Part L compliance report | £400 - £900 |
| BREEAM assessment (design and post-construction) | £2,000 - £6,000+ |
| Passivhaus certification input | £1,500 - £4,000 |
| Part O overheating assessment | £500 - £1,200 |
| Hourly rate | £75 - £135 / hr |
BREEAM assessment fees depend on the project size and credits targeted. Post-construction BREEAM assessments typically add 40-60% to the design-stage fee. Always confirm that the BREEAM assessor is BRE-licensed for your building type - residential, commercial and infrastructure BREEAM schemes require different licences.
Qualifications to look for
The CIBSE Low Carbon Consultant qualification confirms competence in energy modelling, SAP and SBEM calculations, renewable energy systems and Part L compliance. It is the most widely recognised qualification for energy compliance work on UK buildings. Check at cibse.org.
BREEAM assessors must be licensed by BRE (Building Research Establishment) for the specific BREEAM scheme they are assessing. Licensing requires training, examination and ongoing CPD. Check that the assessor's licence covers your building type (domestic, commercial, etc.) at breeam.com.
Passivhaus certification requires a Certified Passivhaus Designer or Consultant to run the PHPP energy balance model. Certification is awarded by the Passivhaus Institut (Germany) or APHA (Passivhaus Trust UK). Check at passivhaustrust.org.uk.
How to find a reputable sustainability consultant
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New Build Cost Calculator Heat Pump Cost Calculator Solar Panel Cost Calculator Extension Cost CalculatorFrequently asked questions
What is a SAP calculation?
SAP stands for Standard Assessment Procedure - the government-approved method for calculating the energy performance of new dwellings in the UK. SAP 10.2 is the current version. A SAP calculation is required for Building Regulations compliance under Part L1A for new homes, and for producing the Energy Performance Certificate (EPC) for new dwellings. It takes account of the building fabric, heating system, hot water system, lighting and renewable energy generation.
When is a BREEAM assessment required?
BREEAM is often required by planning conditions on large residential developments, commercial and public buildings, and publicly funded schemes. Many local planning authorities require BREEAM Very Good or Excellent as a planning condition. Some funding bodies - including Homes England - require specific BREEAM ratings on housing schemes. The requirement is always set out in the planning permission or funding conditions.
What is Part O?
Part O is the part of the Building Regulations covering overheating in new residential buildings, introduced in June 2022. It requires designers to demonstrate that new homes will not overheat in summer using either a simplified compliance method (checking glazing ratios and solar orientation) or a dynamic thermal modelling approach using software such as IESVE or DesignBuilder. Compliance must be demonstrated for bedrooms and living rooms specifically.