SAP 10.2 Explained: The Self-Builder's Guide to Passing Part L
Introduction
The move to the Home Energy Model (HEM) in 2026 has made BREL reports mandatory. We break down the Target Primary Energy Rate (TPER) and how to pass final audits.
The Shift to SAP 10.2 and HEM
The transition from SAP 10.1 to SAP 10.2 (and the upcoming Home Energy Model) represents the most significant change to UK building energy assessment in a decade. For self-builders, this means:
- More stringent Target Primary Energy Rates (TPER)
- Mandatory photographic evidence of thermal junctions (BREL reports)
- Greater scrutiny of 'as-built' performance vs. design calculations
- Increased penalties for non-compliance
What is a BREL Report?
BREL (Building Regulations Evidence List) reports are now mandatory for all new builds. This means photographic evidence of:
- Every thermal junction (wall-to-floor, wall-to-roof, window reveals)
- Insulation installation before plasterboard
- Airtightness membrane continuity
- Service penetrations and their sealing
These photos must be taken during construction—you can't retrofit this evidence. If your Building Control Officer requests BREL documentation and you can't provide it, your completion certificate will be withheld.
Understanding TPER and TER
Two critical metrics determine Part L compliance:
Target Emission Rate (TER): The maximum CO2 emissions your home is allowed to produce per m² per year. This is set by Building Regulations and gets stricter every update cycle.
Target Primary Energy Rate (TPER): The total primary energy your home consumes (including generation and transmission losses). Under SAP 10.2, your design must demonstrate that TPER < TER.
The challenge? TER targets for 2026 builds assume:
- Fabric-first design with exceptional U-values
- No fossil fuel heating (heat pumps are now baseline)
- Significant on-site renewable generation (solar PV)
- High-efficiency MVHR ventilation
How IntegraVolt Ensures First-Time Pass
Our compliance process is designed to eliminate surprises:
- Early SAP Assessment: We model your design before Planning submission
- BREL Documentation: We provide a shot list for your builder to follow
- Airtightness Strategy: We specify details that achieve <3 m³/h/m² at 50Pa
- Thermal Bridge Analysis: We calculate psi-values for every junction
- As-Built Verification: We attend site to verify installation matches design
The result? Our clients pass Building Control inspection first time, with no costly remediation or delays to occupation.
Written by the Integravolt Technical Team
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Consultant's Corner
Pro Tip: When documenting your project for VAT purposes, photograph every thermal junction before plasterboard goes up. This evidence becomes critical if HMRC audits your claim.
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