Numbers you can check,all the way down.
Compliance engines for the standards, our own physics engine for the home, one governed model that carries both, and the certified data they calculate against. This page is written for the people who check.
We build our engines ourselves. All of them.
SAP 10.3
The assessment standard in force today. We built our own engine for it.
Home Energy Model
The standard that replaces it. We built our own engine for that too.
Our physics engine
Bespoke, and ours alone. It represents the whole home as one physical system, fabric, air, emitters, plant and controls, and it stays true to the home as evidence arrives. It works alongside the models you already have.
The jobs are different, and both matter. The compliance engines make a number admissible. The physics engine makes it true to the home. The model carries both.
Owning the engines matters when a figure is questioned. There is no vendor to wait for. We open the calculation and answer.
- Both calculation engines are cross-validated against output from government-approved SAP software.
Edge cases do not show up in ten runs.
They show up in millions. Running the engines at housing stock scale is how we find the cases a demo never meets.
- The Home Energy Model, run at 20 million home scale.
- The same engines power a reconstruction of UK housing stock covering around 18 million dwellings.
The two figures measure different things. 20 million homes is engine throughput: the scale we have run the Home Energy Model at. 18 million dwellings is reconstruction coverage: how much of the UK's roughly 30 million homes the stock reconstruction describes.
The model does not die at handover.
At t=0
The model produces design calculations that are admissible against EN 12831.
In operation
The same model carries forward. Calibration keeps it true to the home as built and as run.
Across the boundary
Provenance is governed. The operating model keeps its design lineage.
Design tools usually stop at the standard. Operational analytics usually start cold, with no design lineage. We hold one model across the boundary, the compliance engines anchoring design, the physics engine carrying the home in operation, so each end stays checkable against the other.
- One model, two admissibilities: compliance-admissible at design time and calibration-true in operation, with governed provenance across the boundary.
Governed by construction.
A number is only worth checking if you can see where it came from. These are not policies. They are what the shipped platform enforces.
Viewpoint conformance
Every screen resolves against a governed viewpoint. What you read is a checked view of the model, not a copy that can drift.
Validation status on every claim
Every number carries its source and its validation status, including the red ones. Failure stays visible until it is fixed.
Journaled actions
Every outbound action requires an approval token and lands in an append-only journal, so what happened is on the record.
- A live governed platform: every screen resolves against a governed viewpoint, and every claim carries its validation status, including the red ones.
Certified products, not defaults.
A calculation is only as good as the product data underneath it. The exhibit below is the certified library we calculate against: 9,300 certified heat pumps, drawn from the public record.
Drawn from 9,300 certified systems currently held in the library.
We publish our working.
The HEM Technical Reference sets out the Home Energy Model as we run it, stage by stage, with the equations. If you want to check our understanding of the standard, start there.
The reference will not answer everything. For the questions it does not cover, ask the people who built the engines.