# Demand: Building Code Definition

> How the IRC 2009 define demand, where the wording differs, and which chapters depend on the term.

- Canonical: https://harth.build/resources/glossary/demand/
- Last updated: 2026-09-07
- Data source: Definitions quoted from the 2009 International Codes as transcribed in this site's building-codes collection, with the source chapter linked for each quotation. Usage counts are computed over the chapters hosted here, one copy per code. The [ICC code library](https://codes.iccsafe.org/codes) publishes the current model text and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-adoption-maps/) show which edition a jurisdiction has adopted; those sources control.

## Key facts

| Fact | Value |
| --- | --- |
| Defined in | IRC 2009 (2009 editions transcribed in this corpus) |
| Primary source | IRC 2009 Fuel Gas (model text, not a jurisdiction's adopted text) |
| Chapters using the term | 17 (counted across the codes hosted here) |
| Wording identical across codes | Single code (compare before citing one code's wording under another) |

## Direct answer

Demand is a defined term in the International Residential Code (IRC) 2009, in Fuel Gas. The code's own words are: “The maximum amount of gas input required per unit of time, usually expressed in cubic feet per hour, or Btu/h (1 Btulh = 0.2931 W).” No other I-Code in this corpus defines it, so the IRC 2009 definition is the one to work from. The term is used in 17 chapters of this corpus, most often in Fire Protection Systems (IFC 2009), Fire Protection Systems (IBC 2009), Existing Structures (IBC 2009). These pages transcribe the 2009 model text; verify the definition against the edition and amendments your authority having jurisdiction has adopted. Record the jurisdiction, the adopted edition, the application date and any local amendment that rewrites the definition before you use it on a live project, because a term redefined by amendment changes every requirement that depends on it.

*Content and cited inputs reviewed by [Scott Barrington](https://nz.linkedin.com/in/barrington), Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.*

## What does this term mean?

**Demand** — IRC 2009, Fuel Gas:

> The maximum amount of gas input required per unit of time, usually expressed in cubic feet per hour, or Btu/h (1 Btulh = 0.2931 W).

![Labeled code-term definition diagram: Demand: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/demand/diagram-1344.webp)

*How the IRC 2009 define demand, where the wording differs, and which chapters depend on the term.*

## What must be verified before using this guidance?

**Demand** is defined once in this corpus, in the [Fuel Gas](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) chapter of the International Residential Code (IRC) 2009:

> The maximum amount of gas input required per unit of time, usually expressed in cubic feet per hour, or Btu/h (1 Btulh = 0.2931 W).

## Where demand is used in the code

The term appears in 17 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [Fire Protection Systems](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/fire-protection-systems.md) | IFC 2009 | 38 |
| [Fire Protection Systems](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/fire-protection-systems.md) | IBC 2009 | 33 |
| [Existing Structures](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/existing-structures.md) | IBC 2009 | 20 |
| [Commercial Energy Efficiency](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/commercial-energy-efficiency.md) | IECC 2009 | 20 |
| [Branch Circuit and Feeder Requirements](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/branch-circuit-and-feeder-requirements.md) | IRC 2009 | 14 |
| [Fuel Gas](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) | IRC 2009 | 6 |
| [Water Supply and Distribution](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/water-supply-and-distribution.md) | IRC 2009 | 6 |
| [Structural Tests and Special Inspections](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/structural-tests-and-special-inspections.md) | IBC 2009 | 4 |
| [Building Services and Systems](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/building-services-and-systems.md) | IFC 2009 | 4 |
| [Tents and Other Membrane Structures](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/tents-and-other-membrane-structures.md) | IFC 2009 | 3 |
| [Water Supply and Distribution](https://harth.build/resources/building-codes/us-states/new-hampshire/ipc-2009/water-supply-and-distribution.md) | IPC 2009 | 3 |
| [Administration](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/administration.md) | IECC 2009 | 2 |

_5 further chapters mention the term._

### The term in use

How the code actually writes about demand, quoted from the 2009 text hosted here:

> A single combination water supply shall be allowed provided that the domestic demand is added to the sprinkler demand as required by NFPA 13R.

— [IFC 2009 §903.3.5.1.2](https://harth.build/resources/building-codes/us-states/rhode-island/ifc-2009/fire-protection-systems.md)

> The associated table demand factors shall be applied to the actual load to determine the minimum load for feeders.

— [IRC 2009 §E3704.2](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/branch-circuit-and-feeder-requirements.md)

> Pipingsystemsshall be of such size and so installed as to provide a supply ofgas sufficient to meet the maximum demand and supply gas to each appliance inlet at not less than the minimum supply pressure required by the appliance.

— [IRC 2009 §G2413.1](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md)


## The terms demand is built out of

The definition above leans on 1 other defined term. Each carries its own code definition, and a local amendment to any of them changes what demand covers:

- **[Btu/h](https://harth.build/resources/glossary/btu-h.md)** — IRC 2009: The listed maximum capacity of an appliance, absorption unit or burner expressed in British thermal units input per hour.

## Demand: what to open, and in what order

Every row is a document this term depends on. The [ICC code library](https://codes.iccsafe.org/codes) and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-adoption-maps/) cover the middle rows.

| Check | Where | Confirmed |
| --- | --- | --- |
| Read the definition in the adopted IRC | Fuel Gas | |
| Re-check the requirement that uses it | Fire Protection Systems (IFC 2009) | |
| Re-check the requirement that uses it | Fire Protection Systems (IBC 2009) | |
| Re-check the requirement that uses it | Existing Structures (IBC 2009) | |
| Re-check the requirement that uses it | Commercial Energy Efficiency (IECC 2009) | |
| Confirm the dependent definition | Btu/h | |
| Local amendment to any of the above | Jurisdiction's amendment list | |

**A research aid, not a code determination.** The authority having jurisdiction decides which edition and which amendments apply.

## Where can you explore related guidance?

- [Explore all glossary guidance](https://harth.build/resources/glossary.md)
- [Btu/h: Building Code Definition](https://harth.build/resources/glossary/btu-h.md)
- [Code Official: Building Code Definition](https://harth.build/resources/glossary/code-official.md)
- [Code: Building Code Definition](https://harth.build/resources/glossary/code.md)
- [Fuel Gas: Building Code Definition](https://harth.build/resources/glossary/fuel-gas.md)

## Sources and method

Definitions quoted from the 2009 International Codes as transcribed in this site's building-codes collection, with the source chapter linked for each quotation. Usage counts are computed over the chapters hosted here, one copy per code. The [ICC code library](https://codes.iccsafe.org/codes) publishes the current model text and the [ICC adoption maps](https://www.iccsafe.org/advocacy/code-adoption-maps/) show which edition a jurisdiction has adopted; those sources control.

### Source links

- [codes.iccsafe.org](https://codes.iccsafe.org/codes)

- [iccsafe.org](https://www.iccsafe.org/advocacy/code-adoption-maps/)

## Frequently asked questions

### What is the code definition of demand?

The International Residential Code (IRC) 2009 defines it in Fuel Gas as: “The maximum amount of gas input required per unit of time, usually expressed in cubic feet per hour, or Btu/h (1 Btulh = 0.2931 W).” The 2009 model text is reproduced here; the definition that binds your project is the one in the edition your jurisdiction has adopted, as amended locally.

### Which parts of the code depend on demand?

In this corpus the term is used across 17 chapters, led by Fire Protection Systems in the IFC 2009. Those are the sections whose scope moves if the definition is amended locally, so read them together with Chapter 2 rather than on their own.

### What is the definition of a building code?

Building is a separate defined term. The IBC 2009 defines it as: “Any structure used or intended for supporting or sheltering any use or occupancy.” That is not the same as demand, which the IRC 2009 defines as “The maximum amount of gas input required per unit of time, usually expressed in cubic feet per hour, or Btu/h (1 Btulh = 0.2931 W).” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

### What does "demand" mean?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Fuel Gas: “The maximum amount of gas input required per unit of time, usually expressed in cubic feet per hour, or Btu/h (1 Btulh = 0.2931 W).” It is defined in IRC 2009. Because it is a defined term, whatever the adopted edition says it means is what every section using it means — so check Chapter 2 of that edition and any local amendment before relying on this wording.

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