The Future Homes Standard (FHS) represents a major step forward in the UK’s drive to reduce carbon emissions and improve the energy efficiency of new homes. As part of this transformation, key updates are being made to the Building Regulations, including Part L (Conservation of Fuel and Power) and Part O (Overheating).
To support compliance with these changes, the government is also replacing the longstanding SAP (Standard Assessment Procedure) with the Home Energy Model (HEM) – a new, more detailed method of assessing home energy use. However, since HEM is not yet fully ready for adoption, an interim version of SAP – SAP 10.3 – is being introduced.
In this article, we’ll explain how the 10.3 update fits into the rollout of the Future Homes Standard 2025, what it means for developers, and how to stay compliant during the transition.
What is SAP 10.3?
SAP 10.3 is a transitional update to the UK’s energy assessment methodology for new and existing domestic dwellings. It forms part of the broader evolution from SAP to the Home Energy Model (HEM) but retains the core framework that developers and assessors are familiar with.
Why is SAP 10.3 Needed Now?
While the Home Energy Model will eventually become the default methodology for assessing domestic energy performance, it is still under development. Some critical elements are not yet ready for industry-wide use.
To avoid regulatory gaps or confusion, SAP 10.3 acts as a temporary but robust compliance route. It ensures consistency and continuity while still aligning with the ambitions of the Future Homes Standard.
When Will SAP 10.3 Come into Effect?
SAP 10.3 is expected to be introduced as part of the upcoming changes to Part L Building Regulations 2025. As the Future Homes Standard is phased in, developers can use either methodology – SAP 10.3 or the Home Energy Model – for demonstrating compliance.
The Future Homes Standard: A Quick Overview
The Future Homes Standard (FHS) is a new criterion for energy performance in domestic dwellings. Coming into force in 2025, it aims to reduce carbon emissions from new homes by:
- Improving energy efficiency through better insulation and airtightness
- Replacing fossil fuel heating with low-carbon systems such as heat pumps
- Supporting the UK’s broader net zero targets for 2050
It marks a key shift in how homes are designed, built, and assessed, which means important updates to Part L and Part O Building Regulations.
How SAP 10.3 Supports Compliance with the FHS
SAP 10.3 introduces a range of technical changes to ensure energy assessments are more aligned with the Future Homes Standard 2025. These include:
- A new notional dwelling specification for benchmarking compliance
- Updated carbon emission factors to reflect the UK’s lower-carbon electricity grid
- Revised assumptions for heating, lighting, hot water, and appliance energy use
Crucially, the 10.3 update builds on the current system rather than replacing it – making it easier for developers and assessors to adapt.
How Developers Should Prepare
Although the regulations are evolving, the principles remain consistent: better fabric, smarter systems, and early planning. Here’s how developers can get ready for SAP 10.3 and new house standards under the FHS.
1. Upgrade the Building Fabric
- High-Performance Insulation: Improve thermal efficiency across walls, roofs, and floors.
- Airtightness: Reduce air leakage and improve overall heat retention.
- Thermal Bridging: Identify and treat junctions to limit unnecessary heat loss.
2. Implement Low-Carbon Systems
- Heat Pumps: Consider air or ground source systems as standard.
- Renewables: Use solar PV where feasible to reduce grid reliance.
- Heat Networks: Explore district heating in high-density developments.
3. Rethink Ventilation Strategies
As homes become more airtight, effective ventilation becomes essential.
- MVHR Systems: Install mechanical ventilation with heat recovery (MVHR) systems to combine energy efficiency with indoor air quality.
- dMEV Systems: Explore decentralised mechanical ventilation (dMEV) systems to replace trickle vents in airtight builds.
4. Plan for Compliance Early
- Use SAP 10.3 tools as soon as they’re available to model new designs.
- Carry out TM54 assessments to identify overheating and performance risks.
- Calculate projected EPC ratings to meet consumer and regulatory expectations.
Why SAP’s Latest Iteration Matters
The 10.3 update gives developers a stable route to compliance while the Home Energy Model (HEM) is being finalised. It gives the industry time to adapt to evolving regulations while still driving forward improvements in energy performance.
Work with Stroma to Stay Ahead
With over 20 years of experience delivering SAP calculations and building performance advice, Stroma is supporting developers through the transition to SAP 10.3 and the Future Homes Standard.
Our team can guide you through changing regulations and help you achieve compliance with confidence.
Our SAP Services:
- Design Stage SAP Calculations – Predict energy performance early in the design
- As-Built SAP Calculations – Verify actual energy performance after construction
- U-Value Calculations – Understand the thermal performance of building elements
- Predicted EPCs – Assign each property a SAP score, placing them on EPC bands A-G
- AutoBrel – Simplify photographic evidence collection for BREL reports
We’re already supporting clients with SAP 10.3 and helping them prepare for the full implementation of the Home Energy Model. Visit our SAP Calculation Services page or get in touch today to discuss your upcoming projects.
FAQs About SAP 10.3
What is SAP 10.3 used for?
SAP 10.3 is a temporary methodology used to demonstrate compliance with energy efficiency regulations while the Home Energy Model is finalised.
When does the Future Homes Standard come into effect?
The Future Homes Standard is being implemented from 2025 onwards as part of updates to Building Regulations, including Part L and Part O. Speak to our team for guidance on upcoming changes.
How does SAP 10.3 affect new build design?
It encourages the use of improved fabric, low-carbon heating, and smarter ventilation strategies – aligning new homes with future compliance requirements and energy performance goals.