When you’re planning a new build project, it’s essential to comply with Building Regulations Part L to ensure your project is energy efficient and environmentally friendly. SAP Calculations (Standard Assessment Procedure) play a key role in this process, especially for new builds. Here, we answer the most common questions about SAP calculations for new builds and how to achieve compliance.
If you’re building or converting a residential property in the UK, you’ve probably heard the term SAP calculations thrown around. But what exactly are they, and why are they essential?
Whether you’re applying for Building Control approval or preparing to sell or rent a home, SAP calculations are a legal requirement. In this post, we break down the entire SAP calculation process—clearly, step-by-step—so you know exactly what to expect.
What Are SAP Calculations?
SAP stands for Standard Assessment Procedure, and it’s the UK government’s method for assessing the energy performance of residential dwellings.
A SAP calculation measures:
- The energy efficiency of the property,
- CO₂ emissions
- Expected energy use for heating, hot water, and lighting
The results are used to produce an Energy Performance Certificate (EPC) and to demonstrate compliance with Part L of the Building Regulations.
If you’re working on a new build, a conversion, or certain extensions, SAP calculations are not optional—they’re required.
The SAP Calculation Process: Step-by-Step
1. Gather the Right Information
Before any calculations happen, your SAP assessor will need:
- Full architectural plans
- Wall, floor, and roof build-ups
- Window and door specs
- Heating and hot water system details
- Ventilation strategy
- Insulation levels (U-values)
Tip: The more accurate your design info, the smoother the process.
2. Data Entry into SAP Software
An accredited assessor inputs all this into government-approved SAP software. The software models how much energy the home will use annually, based on:
- Property size and shape
- Orientation and shading
- Heating efficiency
- Insulation and air tightness
- Use of renewable technologies (e.g. solar PV)
3. Calculate Energy Use and Emissions
The software outputs key metrics:
- DER (Dwelling Emission Rate) – predicted CO₂ emissions
- DFEE (Dwelling Fabric Energy Efficiency) – how well the building envelope performs
- DPER (Dwelling Primary Energy Rate) – predicted primary energy needed
If the property fails to meet targets, design tweaks will be needed.
4. Recommend Adjustments (If needed)
This is where your SAP assessor can add real value. If your current design fails, they’ll suggest practical, cost-effective changes like:
- Upgrading insulation
- Improving boiler or heat pump efficiency
- Adding solar panels
- Switching to LED lighting
- Using mechanical ventilation with heat recovery (MVHR)
5. Issue SAP Report and Predicted EPC
Once your design passes, the SAP assessor issues:
- A full SAP Report
- A Predicted Energy Assessment (PEA) if the building isn’t yet finished,
- Part L Compliance Pack summarising the above
These are submitted to Building Control and may also be required by lenders, insurers, or warranty providers.
6. Final SAP Assessment and EPC
After construction, a final assessment ensures the property was built to spec. Any changes during construction must be reflected in the updated SAP data.
You’ll need:
- Final air tightness test results
- Confirmation of materials and systems used
- Updated EPC based on actual build data
The final EPC is valid for 10 years and must be lodged before the property is sold or rented.
When Do You Need SAP Calculations?
You need SAP calculations for:
- New build homes
- Barn or commercial conversions
- Flats created from one larger property
- Extensions with significant glazing
Don’t Leave SAP Calculations to the Last Minute
SAP calculations aren’t just paperwork—they affect your design and budget. Involving a SAP assessor early helps you design smarter and stay on schedule.
Get Expert SAP Calculations for Your Extension Today!
If you’re planning a new build and want to ensure compliance with Building Regulations, our team of experienced SAP assessors is here to help. We provide a fast, reliable service with tailored advice to meet your needs.
- Call us today: 020 7183 3240
- Email us: [email protected]
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