Britain builds homes it never measures.
Groundtruth is a Cornish housebuilder whose homes prove their promises — running costs and carbon, predicted and published. What we say a home will do is written down before it's built. What it actually does is measured, and published beside it.
A HOUSEBUILDER RUN LIKE A LEVELLING SURVEY: EVERY CLAIM CLOSES BACK TO A BENCHMARK.
Every new home comes with numbers. Almost none are ever checked.
Energy models, running-cost estimates, carbon figures — produced at design stage, printed in the brochure, and then never compared with what the finished building actually does. The industry calls the difference the performance gap. Buyers call it a surprise bill.
The gap persists because measurement is nobody's job. The designer has moved on, the builder has been paid, and the buyer has no baseline to check against. Groundtruth exists to make measurement the job.
Build. Instrument. Measure. License.
We do the four things in order, and we don't skip the third.
Build
Energy-efficient homes in Cornwall, designed to numbers we're prepared to stand behind.
Instrument
Every home carries its own instruments — temperature, energy, whole-building heat loss — from day one.
Measure
Predicted vs measured, side by side: running costs, energy use, carbon. The delta is published, whichever way it falls.
License
The measurement platform behind our homes — Datum — becomes available to an industry that will need it.
Every home keeps a record. The record can't be quietly revised.
Datum is the platform underneath: an append-only ledger where predictions are written before the result exists, and measured values are recorded beside them as they arrive. Nothing is edited after the fact. A number either held, or it didn't — and either way, it's on the page.
From 2027, new homes in England will be built to a standard that expects performance to be demonstrated, not just modelled. Datum is built for that world.
Four rules, published so you can hold us to them.
Performance, not procurement.
We publish what homes cost to run, use and emit. Commercial terms stay commercial.
Predictions come first.
Every figure is written down before the result exists, and is never revised after it. The delta is the point.
No invented statistics.
Nothing on this site is a projection dressed as a fact. A table appears here when its first row exists in the real world — and not before. That is why this page has no charts yet.
Measured beats modelled.
Where a model and an instrument disagree, we report the instrument.
Proof is useful to everyone except the unprovable.
Buyers
Know what a home costs to run before you commit to it — and see whether our last one did what we said it would. No surprise bills.
Lenders & valuers
Evidence instead of brochures: predicted and measured performance, recorded as it happened, for buildings you're asked to back.
The industry
When demonstrated performance becomes the standard, the builders who measured will license the machinery from those who did. Datum is that machinery.