Twenty years reading buildings, and a PE licence in four states. A large part of the work is checking what a building reports against what the building is actually doing.
Those two things come apart more often than anyone expects. And when they do, the machine is almost always fine. The reporting is the part that broke.
Here is why, because it is not carelessness. It is how the thing is built.
A control screen mostly shows you commands, not measurements.
The controller sends an instruction, open the vent, and then it prints on the screen: vent open. Nothing between those two events checks whether anything moved.
If the little arm that swings the vent is seized, or snapped off, or was never connected to the vent in the first place, the screen says exactly what it says on a good day. It is not reporting the vent. It is repeating the order.
Two kinds of readings sit on that screen. One is measured by something out in the building. The other is typed in by a person, or echoed back from a command. They are in the same font, on the same page, in the same color, and nothing tells you which is which.
Three questions worth asking about any number a building shows you.
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First, is there a sensor at the thing itself, or only an instruction going to it? A vent that reports open because it was told to open is not a reading.
Second, who can type over it? A target temperature, a schedule, a label, an alarm limit. A person can change any of those in a few seconds, and nothing on the screen records that they did. A number a person typed is a preference, not a fact.
Third, does anything outside the building agree? That one gets skipped, and it is the strongest of the three, because there is exactly one instrument in your building that nobody inside the building can program.
The meter.
The utility owns it. It measures what actually moved through the pipe or the wire. Nobody at the property can edit it, and it produces a document every month whether anyone reads it or not.
One of the strangest things I have found in a building turned up that way. The building had been signed off as fully tested. Its heated floor was running at 90 degrees in the middle of summer while the cooling system fought it back down to 70 in the same room. Nothing alarmed, nothing lit up, no screen complained. It showed up as a number on a gas bill.
When the screen and the bill disagree, the bill is right.
Ask for the history, not the number.
There is one more move, and it is the fastest way to find a dead sensor without touching anything.
Do not ask what the temperature is. Ask to see what it has been. Every one of these systems keeps a trend log, and almost nobody opens it, because the current value is right there on the front page and looks like an answer.
A live sensor is never still. Put a week of it on a chart and you get a line that wanders, because the real world wanders. Temperature drifts with the sun and the occupancy. Pressure moves when things turn on. The line is noisy, and the noise is the proof it is connected to something.
A dead sensor gives you a flat line. Exactly the same number, hour after hour, for days. People read that as a well-controlled building. It is the opposite. Nothing in a building holds a value that perfectly, so a perfectly held value means the reading stopped coming from the world and started coming from the last thing written down.
Same tell in the other direction: a value that only ever changes when somebody was on site is not a measurement either.
Ask for a month of trends on the three or four things you care about most. It costs an email, and it will tell you more about whether that building is actually being run than any walkthrough will.
And at purchase, ask for the bills.
If you are buying, everything above collapses into one request. Take the utility history, twenty-four months of it, and treat the control system screenshots as marketing material.
The screenshots come from a system the seller’s people configure. The bills come from a company with no stake in the transaction, measuring what physically moved. One of those is a claim and the other is a record, and only one of them will still be true after closing.
The rule I work from is short. A system reporting fine is not evidence that it is fine. When the call is too hot, too cold, or too expensive, dig every component.
And this is not a handful of unlucky buildings.
LBNL studied 317 of them in 2023 and found that on any given day, 40% of the air handlers, the big machines that push air around a building, are carrying a reported fault.
Read that word again. Reported. The fault was not hiding. Something found it and wrote it down. Four in ten of those machines have already filed the report.
The building did its part. It noticed, it logged it, and then it went back to displaying whatever it was told to display, on a screen that is usually the cleanest object in the room.
Reading is the part that was never automated. It still is not.
—Jon
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