Building Code Glossary
Conditioned Air: Building Code Definition
How the IRC 2009 define conditioned air, where the wording differs, and which chapters depend on the term.
On this page
Last updated September 7, 2026 · 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.
Direct answer
Conditioned air is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “Air treated to control its temperature, relative humidity or quality.” 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 9 chapters of this corpus, most often in Duct Systems (IRC 2009), Foundations (IRC 2009), Definitions (IMC 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, Harth founder and architectural technology specialist · Published 2026-09-07 · Updated 2026-09-07.
What does this term mean?
Conditioned Air — IRC 2009, Definitions:
Air treated to control its temperature, relative humidity or quality.
What must be verified before using this guidance?
Conditioned Air is defined once in this corpus, in the Definitions chapter of the International Residential Code (IRC) 2009:
Air treated to control its temperature, relative humidity or quality.
Where conditioned air is used in the code
The term appears in 9 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.
| Chapter | Code | Mentions |
|---|---|---|
| Duct Systems | IRC 2009 | 3 |
| Foundations | IRC 2009 | 3 |
| Definitions | IMC 2009 | 2 |
| Definitions | IRC 2009 | 2 |
| Definitions | IBC 2009 | 1 |
| Roof Assemblies and Rooftop Structures | IBC 2009 | 1 |
| Definitions | IECC 2009 | 1 |
| Definitions | IFC 2009 | 1 |
| Refrigeration | IMC 2009 | 1 |
The term in use
How the code actually writes about conditioned air, quoted from the 2009 text hosted here:
Joints and all refrigerant-containing parts of a refrigerating system located in an air duct of an air-conditioning system carrying conditioned air to and from human-occupied space shall be constructed to withstand, without leakage, a pressure of 150 percent of the higher of the design pressure or pressure relief device setting.
Conditioned air supply sized to deliver at a rate equal to 1 cubic foot per minute (0.47 Lis) for each 50 square feet (4.7 m2) of under-floor area, including a return air pathway to the common area (such as a duct or transfer grille), and perimeter walls insulated in accordance with Section N1102.2.9;
The terms conditioned air 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 conditioned air covers:
- Control — IRC 2009: A manual or automatic device designed to regulate the gas, air, water or electrical supply to, or operation of, a mechanical system.
Conditioned Air: what to open, and in what order
Every row is a document this term depends on. The ICC code library and the ICC adoption maps cover the middle rows.
| Check | Where | Confirmed |
|---|---|---|
| Read the definition in the adopted IRC | Definitions | |
| Re-check the requirement that uses it | Duct Systems (IRC 2009) | |
| Re-check the requirement that uses it | Foundations (IRC 2009) | |
| Re-check the requirement that uses it | Definitions (IMC 2009) | |
| Re-check the requirement that uses it | Definitions (IRC 2009) | |
| Confirm the dependent definition | Control | |
| 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
- Control: Building Code Definition
- Building: Building Code Definition
- Construction Documents: Building Code Definition
- Registered Design Professional: Building Code Definition
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 publishes the current model text and the ICC adoption maps show which edition a jurisdiction has adopted; those sources control.
Source links
Frequently asked questions
What is the code definition of conditioned air?
The International Residential Code (IRC) 2009 defines it in Definitions as: “Air treated to control its temperature, relative humidity or quality.” 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 conditioned air?
In this corpus the term is used across 9 chapters, led by Duct Systems in the IRC 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 considered conditioned space in a building?
Conditioned Space is a separate defined term. The IRC 2009 defines it as: “For energy purposes, space within a building that is provided with heating and/or cooling equipmentor systems capable of maintaining, through design or heat loss/gain, 50°F (IO°C) during the heating season and 85°F (29°C) during the cooling season, or communicates directly with a conditioned space. For …” That is not the same as conditioned air, which the IRC 2009 defines as “Air treated to control its temperature, relative humidity or quality.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.
What does conditioned air mean?
In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “Air treated to control its temperature, relative humidity or quality.” 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.
What is the US-SIC code for Air Conditioning?
Air Conditioning is a separate defined term. The IMC 2009 defines it as: “The treatment of air so as to control simultaneously the temperature, humidity, cleanness and distribution of the air to meet the requirements of a conditioned space.” That is not the same as conditioned air, which the IRC 2009 defines as “Air treated to control its temperature, relative humidity or quality.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.
Related pages
- Condensate: Building Code Definition
Condensate — IRC 2009 definition: The liquid that separates from a gas due to a reduction in temperature, e.g., water that …
- Condenser: Building Code Definition
Condenser — IMC 2009 definition: A heat exchanger designed to liquefy refrigerant vapor by removal of heat.
- Condensing Appliance: Building Code Definition
Condensing Appliance — IRC 2009 definition: An appliance that condenses water generated by the burning of fuels.
- Conditioned Area: Building Code Definition
Conditioned Area — IRC 2009 definition: That area within a building provided with heating and/or cooling systems or appliances capable of maintaining …
- Conditioned Floor Area: Building Code Definition
Conditioned Floor Area — IRC 2009 definition: The horizontal projection of the floors associated with the conditioned space.
- Conditioned Space: Building Code Definition
Conditioned Space — IRC 2009 definition: For energy purposes, space within a building that is provided with heating and/or cooling equipmentor systems …