Services
NCC Performance Solutions
When a heat pump system's real operating duty does not match the NCC 2025 J6D10 test condition, the Deemed-to-Satisfy COP threshold is the wrong yardstick. We build the Performance Solution case instead: a performance-based design brief agreed with your building surveyor, annual energy modelling against a code-minimum reference, and a report structured to NCC clause A2G2.
Why the DtS test condition doesn't fit every system
NCC 2025 Part J6 sets energy efficiency provisions for heated water systems, including systems used for space heating. Clause J6D10 is the Deemed-to-Satisfy (DtS) provision: it requires a capacity-weighted COP of at least 3.14, assessed at a single EN 14511 intermediate rating condition (7°C air, water 40°C in to 45°C out, a lift of roughly 5K).
That condition describes a low-lift duty. Systems delivering water at much higher temperatures, such as CO2 or other high-temperature heat pumps supplying a hydronic space heating loop at 60°C or more, are rarely tested at 40/45°C and cannot deliver that duty at all. Measured against the DtS condition, a system built and tested for a genuinely different duty can show a COP well below 3.14, even where it is the more efficient choice for the duty it actually performs.
J6D10 is a Deemed-to-Satisfy provision, not a mandatory one. NCC clause A2G1 makes clear that DtS Provisions are never the only compliance path: the binding requirement underneath J6 is Performance Requirement J1P1, on operational energy use and greenhouse gas emissions. A2G2 sets out a Performance Solution route to demonstrate compliance with J1P1 directly, without being held to the DtS test condition.
The Performance Solution route under A2G2
A2G2(1)(b) sets a lower bar than proving J1P1 compliance outright: the solution needs to be at least equivalent to the Deemed-to-Satisfy Provisions. A2G2(2) lists several ways to demonstrate that. We stack three of them, because each corroborates the others.
Evidence of suitability
Your EN 14511 or equivalent performance test report, at the conditions that reflect real operating duty.
Expert judgement
An EnergyAE engineering report reasoning from first principles why the system is at least equivalent to the Deemed-to-Satisfy outcome.
Comparison with DtS
Annual energy and emissions modelling against a code-minimum reference system delivering the same duty, same climate.
The design brief comes first, not last
A2G2(4) makes a performance-based design brief mandatory before the analysis is done: the scope, the method, and the acceptance criteria are agreed with your building surveyor upfront. A report alone, produced after the fact, is not sufficient. Getting the brief signed off early is what stops the method being challenged after the modelling is complete.
What we provide
A three-stage engagement, run against the acceptance criteria your surveyor has already agreed to.
1
Design brief
A performance-based design brief (PBDB) scoping the assessment, method, and acceptance criteria, agreed with your building surveyor before any modelling starts.
2
Annual modelling
TRNSYS-based annual energy and GHG emissions modelling of your system against a code-minimum reference unit, matched for duty and climate.
3
Performance Solution report
A report stacking all three A2G2 assessment methods, structured to the acceptance criteria your surveyor already agreed to.
The annual modelling uses the same TRNSYS engine and AS/NZS 4234 methodology we apply across our incentive scheme work, adapted to compare your system's real duty against a code-minimum reference sized and configured to deliver the same duty in the same climate. Every assumption made in the reference's favour is disclosed and swept for sensitivity, so the comparison stands up to scrutiny rather than being read as favourable to the system under assessment.
When this applies
- High-temperature or high-lift heat pump systems (including CO2/transcritical units) used for commercial space or process heating, where the real delivery temperature sits well above the low-lift J6D10 test condition
- Systems that fail, or would fail, the J6D10 Deemed-to-Satisfy COP threshold on paper but are demonstrably efficient at their actual operating duty
- Product ranges installed across multiple sites, where a Performance Solution built for one configuration establishes a methodology that carries across future projects using the same equipment
- Any heat pump water heating equipment where the manufacturer's test data was never generated at the DtS rating point
What we need to start
- EN 14511 (or applicable) performance test report, covering the ambient and water temperature range the system actually operates across
- System schematic or P&ID: heat pump, storage, valves, and any hydraulic separation
- Control logic: delivery setpoint, deadband, staging, and how the setpoint is determined on site
- Site location and NCC climate zone
- Operating schedule and target duty (delivery temperature, load profile) if known
- Building surveyor contact, if one is already engaged
No performance test data at the duty your system actually operates at? Tell us what testing exists and we will confirm what else is needed before quoting.
Discuss a Performance Solution for your system
Send us your system's performance data and duty, and whether a building surveyor is already engaged. We will confirm what a Performance Solution assessment would involve and provide a fixed-fee quote.