# Division 25 vs 23 09 00: Where Controls Scope Lives

Why building automation scope shows up in Division 25, in 23 09 00, in process and electrical sections all at once, how they cross-reference, and the bid-time sweep that finds every section that touches you.

You bid 23 09 23, the DDC section, and you bid it well. After award the GC forwards a submittal register with three Division 25 sections on it you never opened: one for the network, one for integration of third-party systems, one for graphics and the operator workstation. Then the electrical engineer asks when the lighting control interface submittal is coming, because a paragraph in Division 26 says the BAS contractor provides it. None of it was hidden. It was just spread across four divisions, and you read one.

This article is a map of where building automation and controls scope lives, why the same book often uses more than one home for it, and how to sweep a book at bid so nothing surfaces after award.

## What each home is for

**23 09 00, Instrumentation and Control for HVAC.** The traditional home of the building automation system, written by the mechanical engineer as part of the HVAC spec. Inside it you will usually find the field devices, the DDC system itself at 23 09 23, and the sequences of operation at 23 09 93. Because the mechanical engineer writes it, it is HVAC first: air handlers, terminal units, central plant. Anything outside HVAC tends to show up as an afterthought or not at all.

**Division 25, Integrated Automation.** Added in MasterFormat 2004 to give building-wide automation its own division, for control systems that span HVAC, electrical, plumbing, lighting, and security. Its structure mirrors a controls job: common work results at 25 05 00, network equipment at 25 10 00, instrumentation and terminal devices at 25 30 00, facility controls at 25 50 00, and control sequences at 25 90 00. In practice Division 25 is used unevenly. Some books put the whole BAS there. Some use it only for the network and the head end. Some leave it out entirely.

**Division 40, process control.** On water, wastewater, and industrial jobs the controls scope lives in Division 40, and the numbers moved between editions: 40 90 00 held instrumentation and control for process systems in the 2004 through 2012 editions, and books from the 2014 edition on use the 40 6x and 40 7x range for the control system and keep 40 90 00 for primary control devices. A treatment plant with an administration building can carry both a Division 40 process control system and a 23 09 building system, with an interface between them that nobody owns until you ask. The full map of process numbering is in [which CSI divisions a controls integrator actually owns](/learn/csi-divisions-for-integrators).

**Division 26, Electrical.** Rarely your scope, nearly always your interface. It covers the power circuits that feed your panels, VFDs at 26 29 23 when the electrical engineer specifies them, lighting controls in the 26 09 sections, metering, and generator and transfer switch status. Each of those can carry a sentence that hands you a point, an interface, or a submittal.

**The rest.** Fire alarm and security live in Division 28, and smoke control or fan shutdown interlocks put you in the middle of them. Structured cabling and the owner's IT network live in Division 27, which decides who furnishes the switches your controllers plug into. Commissioning is usually 01 91 13 with an HVAC-specific section at 23 08 00, and both name tasks for the controls contractor.

## Why both appear in one book

Division 25 exists, but engineering firms write from their own master specs, and many of those masters grew up with controls in 23 09. So the same book can hold:

- A 23 09 block written by the mechanical engineer from the firm's master, covering HVAC devices and sequences.
- A Division 25 block added for a campus or hospital owner whose BAS standard requires a particular front end, network design, and integration rules.
- A Division 25 section that is a one-paragraph pointer back to 23 09 23, left over from a master.
- Or the reverse: a thin 23 09 section saying all controls work is in Division 25.

None of those is wrong. The mistake is assuming the first controls section you found is the only one. Owner standards are the usual reason for a split: the owner's facilities group cares about the front end, the network, and naming conventions across every building, while the mechanical engineer cares about this building's air handlers. Each writes the part they care about, and the two parts don't always agree.

When they disagree, figure out which governs before you price. Many books carry an order of precedence in Division 01 or the general conditions. If yours doesn't resolve it, that is a bid question or an RFI, not a judgment call. The decision rule is in [submittal vs RFI](/learn/submittal-vs-rfi).

## How the cross-references work

Sections point at each other in a few predictable places.

**Related sections.** Near the top of Part 1, most sections list the sections they depend on. In a controls section this list is your first map. In an equipment section, a line pointing at 23 09 or Division 25 means that equipment touches you.

**Equipment sections.** Air handler, chiller, boiler, pump, and VFD sections often require a factory controller with a network interface for connection to the building automation system, or field-mounted devices furnished by one trade and installed by another. Those paragraphs define your integration scope as much as your own section does, and you only find them by opening the equipment sections.

**Responsibility matrices.** Many books include a matrix, in 23 09 or Division 26, saying who furnishes, installs, wires, and powers each item: starters, VFDs, smoke dampers, actuators, interlocks. Read it line by line against the narrative. Where the two disagree, ask, because the electrician may have priced from the matrix while you priced from the narrative.

**Stale pointers.** Masters get renumbered and sections get cut, but the pointers often survive. A reference to a section that isn't in the book is common. It still needs an answer: ask before bid, or write your assumption into the bid.

## The bid-time sweep

The goal is a list of every section that touches controls, each marked ours, interface, or by others, with a line of reasoning. Here is the order that finds them.

1. **Read the table of contents by title.** Mark everything in 23 09, Division 25, the 26 09 range, the process control range in Division 40, and Division 28. Then read every title in the rest of the book once. "Packaged" and "system" in a title are worth a look.
2. **Search the full text.** Run these terms across the whole book, not just the sections you marked: building automation, BAS, BMS, DDC, temperature control, controls contractor, BACnet, Modbus, LonWorks, Division 25, 23 09, interface, integrate, points list, sequence of operation, monitor, status.
3. **Open every equipment section that hits.** Mechanical equipment first, then electrical: generators, transfer switches, metering, lighting controls. Then plumbing: water heaters, booster pumps, leak detection. These are where the integration points hide.
4. **Read the commissioning sections.** They name your test and documentation tasks, which are labor you need to price.
5. **Mark each section.** Ours, interface, or by others. The interface sections are the ones you read closely and never submit against.
6. **Write bid clarifications for the gaps.** Integration limits, who furnishes network switches, who provides power to your panels. One sentence each.

A table makes the result easy to check against the GC's scope sheets:

| Where | Usually holds | What it usually asks of controls |
|---|---|---|
| 23 09 00 | HVAC devices, DDC system, sequences | Furnish, install, program, submit |
| Division 25 | Front end, network, integration, owner standard | Head end, graphics, third-party integration |
| 23 equipment sections | Factory controls on packaged equipment | Network integration, field devices, wiring |
| Division 26 | Power, VFDs, lighting controls, metering | Status and control points, interface submittals |
| Division 27 | Structured cabling, owner network | Ports, addressing, switch responsibility |
| Division 28 | Fire alarm, security | Smoke control interlocks, monitoring |
| Division 40 | Process control | Plant system and its interface to the BAS |
| 01 91 13, 23 08 00 | Commissioning | Functional testing, trend data, documentation |

Rows vary by book. The point of the table is that every row got checked.

## How Submittal Kit handles this

Controls scope spread across four divisions is how a section slips past the bid. In Submittal Kit you [upload the spec book](/help/upload-specifications) once and the sections roll up under their divisions. Say what you provide on the Scope tab and each line comes back with the section that specifies it. Then open All sections and claim a section or a whole division by hand; that is the way in for a Division 25 or 23 09 section that specifies a system rather than a device. Each claimed section is read for what it requires you to submit, with every demand quoted and its article reference attached, and the [Submittal Log](/help/submittal-log) counts the demands you have not answered yet.

*Disclosure: I build Submittal Kit. The sweep above works the same with a highlighter and a spreadsheet.*

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Submittal Kit · Field Guides · Updated 2026-10-04
Canonical: https://submittalkit.com/learn/division-25-vs-23-09-00