FDD: Turn Wasted HVAC Data Into Real Savings

Most building automation systems are exceptional at collecting data and mediocre at doing anything with it. A typical commercial building’s BAS records tens of thousands of points at one- or five-minute intervals.

The operations team looks at maybe 2% of it. Mostly through alarm screens that fire when something has already failed. The other 98% sits in trend logs that nobody opens until there’s a problem to investigate.

What FDD is

Fault detection and diagnostics — FDD — is the discipline of turning that data into actionable insight. The goal is to surface problems before they become visible to occupants.

Modern FDD software analyzes BAS trend data against expected behavior. Then it surfaces deviations. Examples:

• An economizer that’s not opening when outdoor conditions allow free cooling
• Simultaneous heating and cooling in a single zone
• A supply fan running 24/7 in a space that’s only occupied 8 hours a day
• A discharge air temperature drifting outside its setpoint band
• A valve that never closes

The technology stack

FDD platforms come in a few flavors.

Niagara Analytics is Tridium’s native analytics framework. It runs on the Niagara Supervisor. It works particularly well for sites already standardized on Niagara — no separate integration layer required.

Independent platforms operate above the BAS. They ingest data via BACnet, Modbus, or APIs, and provide vendor-neutral analytics. Examples include SkySpark (SkyFoundry), Clockworks Analytics, and KGS Clockworks. Each has trade-offs in cost, rule library depth, customization capability, and how it presents results.

What FDD finds in a typical building

Industry studies and the experience of practicing engineers converge on similar lists. The persistent top findings in commercial buildings:

• Simultaneous heating and cooling (often 5–15% of zones at any given time)
• Economizer faults (stuck or partial)
• Schedule mismatches (HVAC running outside occupancy)
• Setpoint drift (occupant overrides that never time out)
• Valve leak-through or stiction

None of these are exotic problems. All of them are individually small. Collectively, however, a building with no FDD discipline accumulates 5–20% of HVAC energy waste within 3–5 years of original commissioning.

Where FDD projects fail

The most common failure isn’t technical. Instead, it’s that the FDD platform generates 400 “faults” in the first week. The operations team can’t triage them. As a result, the platform becomes wallpaper.

Successful FDD deployment requires three things beyond the software:

1. A prioritization layer that ranks faults by energy impact and comfort impact. So the team works on the top 20, not all 400.
2. A defined workflow that connects FDD findings to a corrective action process — ticket, assignment, resolution, verification.
3. Ownership. Without a person whose job includes responding to FDD output, the system runs but nothing changes.

The economics

For a 100,000+ square foot commercial building, FDD platforms typically run $0.05–$0.15 per square foot per year in licensing. Implementation labor is on top of that.

Verified energy savings on well-deployed FDD programs run 5–15% of HVAC energy in the first 12 months. Sustained savings of 2–5% per year thereafter, as the program shifts from finding existing faults to preventing new ones.

For institutional portfolios, the per-building cost drops on aggregation. The verification rigor also improves.

Where this is going

The combination of cheap continuous data, mature analytics rules, and increasingly capable AI is shifting FDD. The shift: from “rule-based reports that humans triage” toward “continuous tuning that adjusts setpoints automatically within sanctioned bounds.” That shift requires trust — trust in the underlying data, trust in the model, and trust in the governance around what’s allowed to change automatically. The buildings that get to autonomous operation will be the ones where the FDD foundation was solid first. Read more on our Ongoing Commissioning post.

Talk to Signet Controls. Planning a BAS install, retrofit, integration, or service contract in California? We work across Los Angeles, Orange County, the Inland Empire, the Central Coast, and Kern County. Reach our team at info@signetcontrols.com or call (877) 874-4638.