Start with the fundamentals.
Trace one value. Explain its source, equipment, units, timestamp and intended use. Compare it with a suitable reference and record what you can and cannot conclude.
Data Assurance Commissioning · DACx
Can you trust the data
behind the decision?
At BPV, Marcus uses Data Assurance Commissioning (DACx) to describe a practical approach to verifying building data: follow it from its real source to the place someone uses it, and keep the evidence with it.
Try a practical example ↓What this means
A number needs a source, a meaning and a check.
A value on a dashboard can look reasonable and still describe the wrong equipment, use the wrong units or represent an old reading. Before that value informs an operating decision, understand what it measures and how it arrived.
This matters to energy information, fault detection and diagnostics (FDD), electrical monitoring, analytics and digital twins. Define what information the intended use needs, who delivers it and how it will be verified.
Follow the evidence
120 kW on the screen.
120,000 kW in the export.
These illustrative records claim to describe the same meter at the same time. Is the building using more power, or did the meaning change along the way?
Open each checkpoint to uncover the evidence. Follow the complete path before deciding what to correct.
01 Source record What is being measured?
The source record identifies meter M-01 and a value of 120,000 W. Check the measurement, equipment association and timestamp. This record establishes the reported source value; it does not, by itself, prove the physical meter’s accuracy.
02 Displayed value What conversion occurred?
The display converts watts to kilowatts: 120,000 W ÷ 1,000 = 120 kW. The displayed number and unit are consistent with this source record. Confirm that the correct record and time are being compared.
03 Exported record Did the unit travel with the number?
The export keeps the raw value, 120,000, but labels it kW. In this example, that is a unit-mapping error. The available records do not demonstrate an increase in the building’s load.
04 Correction and retest What would close the issue?
Assign the export correction to the responsible party. Retest source, display and export using matching records; preserve the evidence. Review affected historical exports and downstream calculations before relying on them. Record any remaining limitations.
What else could make apparently matching values misleading?
Different measurement boundaries, stale timestamps, different averaging intervals, missing samples, duplicate records or a reset can all change the interpretation. The exercise isolates one unit error. A real investigation follows the agreed scope and evidence rather than assuming every mismatch has the same cause.
Take it deeper.
Explore naming and metadata, sensor and meter verification, trends, exports, data interfaces, missing-data behavior and change control. Connect checks to the owner’s use and the approved project criteria.
What you practice producing
A data-verification record.
Document the requirement, source, data path, comparison method, expected result, observed result, issue owner and retest evidence. Another person should be able to follow how you reached the conclusion.
Is DACx a separate standard or certification?
DACx is presented here as Marcus’s teaching approach to building-data verification. It is not a claim of a separate ASHRAE or CSI standard or an accredited certification. Applicable standards, project requirements, responsibilities and acceptance criteria still govern the work.
Build your understanding
Bring the question.
Practice the work.
Learn to investigate a mismatch, explain the evidence and produce a useful data-verification record. Start with the fundamentals or bring an approved project example for deeper team training.
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