Future Homes Standard, SAP 10.3 and the Home Energy Model

What Housebuilders need to know and how Galaxy Technical Services can help

As the UK housing sector moves towards more stringent energy standards, housebuilders face a fast-changing regulatory landscape. With the Future Homes Standard (FHS) due in 2025, and the introduction of the Home Energy Model (HEM) due to be announced soon, it’s critical to stay ahead of the curve.

Adding to this evolving picture is the recent Government announcement of SAP 10.3, the final iteration of the SAP methodology before it is succeeded by HEM. For an interim period, these two systems will run in parallel, supporting a smoother transitional phase for compliance and planning.

At Galaxy Technical Services, we’re supporting developers through this shift with practical advice, compliance modelling services, and hands-on testing, ensuring our clients remain compliant, cost-effective, and future-ready.

What's changing and why it matters

The Future Homes Standard (FHS)

Coming into force in 2025, the FHS will require new homes to:

• Produce 75–80% fewer carbon emissions than those built to 2013 standards.
• Ban on fossil-fuel heating systems, such as gas and oil, with electric heating (particularly heat pumps) to become the norm
• Deliver high insulation, airtightness, and potentially include solar PV and MVHR.

This will raise the bar for building fabric, services, and energy performance.

SAP 10.3: The final step before HEM

SAP 10.3 has been recently announced as the last planned update to the existing SAP 10 methodology:

• It features updated carbon factors, reflecting the decarbonisation of the electricity grid.
• Heat pumps now perform more favourably, encouraging their use even before FHS fully comes into force.
• Greater accuracy in assessing lighting, hot water usage, and ventilation.

For a transitional period, SAP 10.3 will continue to be used for compliance under current Building Regulations, including for homes that will be completed before 2025, before being succeeded by the new Home Energy Model (HEM).

Home Energy Model (HEM): The future of compliance

From 2025, HEM will eventually replace SAP as the regulatory compliance tool for new homes built to the Future Homes Standard.

HEM is a next-generation, hourly energy model that:

• More accurately reflects real-world occupancy and usage.
• Introduces transparent, open-source logic.
• Improves consistency between predicted and actual energy use.

What this means for Housebuilders

1. Navigating the SAP 10.3 to HEM transition

For projects that will fall under the new FHS regulations

• Both SAP 10.3 and HEM methodologies will be allowed to be used during a phased transition - the timelines of which will become clearer soon.
• Once the dual methodology transition period ends, developments will be expected to be designed and built to FHS using the HEM methodology solely.

Galaxy Technical Services will help you model under both systems, so you’re covered no matter your development timeline. Our dual-approach strategies ensure you're not caught out by mid-project regulatory changes.

2. Revisiting building fabric and M&E choices

The combined changes across FHS, SAP 10.3, and HEM make it essential to revisit:

• Insulation levels, airtightness, and ventilation.
• Low-carbon technologies, such as air source heat pumps, solar PV, and MVHR.
• Internal layouts and orientations for solar gain and energy efficiency.

We work with your architects and design teams to ensure your specifications align with future standards, without adding unnecessary cost.

3. Cost, feasibility, and supply chain risk

We know that cost remains a key concern, especially during a time of material and labour pressures. With our support, you can:

• Evaluate cost-effective compliance routes using SAP 10.3 initially and ultimately HEM.
• Avoid over-specification or costly redesigns by planning with both models in mind.
• Prepare your procurement and build teams for technologies that are set to become standard.

4. QA, Testing and In-Use Validation

HEM places greater emphasis on measured performance. That means build quality, detailing, and commissioning will all face greater scrutiny.

Galaxy offers a full suite of services including:

• Thermal bridging assessments
• U-Values with Condensation Risk Analysis 
• Technical specification
• Use of GTS photographic evidence App for the BREL Report 
• Overheating TM59 calculations 
• Water efficiency calculations
• Air tightness testing
• Ventilation testing 
• Acoustics testing 
• EPC 

Our pre-completion testing and compliance reporting ensure you meet expectations at every stage.

How Galaxy Technical Services Supports You

Final Thoughts

This is a complex time for housebuilders but also an exciting one. The transition with SAP 10.3 and the introduction of the Home Energy Model are not just about compliance they’re about building better homes that are ready for the future.

At Galaxy Technical Services, we’re not just watching the changes happen we’re helping shape how our clients respond to them.

Let us help you take the guesswork out of compliance and turn these changes into a competitive advantage.

Contact us today to talk about your pipeline, and how we can support you from design through to completion.