# Air Barrier: Building Code Definition > How the IRC 2009, IECC 2009 define air barrier, where the wording differs, and which chapters depend on the term. - Canonical: https://harth.build/resources/glossary/air-barrier/ - 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, IECC 2009 (2009 editions transcribed in this corpus) | | Primary source | IRC 2009 Definitions (model text, not a jurisdiction's adopted text) | | Chapters using the term | 4 (counted across the codes hosted here) | | Wording identical across codes | Yes (compare before citing one code's wording under another) | ## Direct answer Air barrier is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “Material(s) assembled and joined together to provide a barrier to air leakage through the building envelope. An air barrier may be a single material, or a combination of materials.” The IECC 2009 carries the same definition word for word, so the term means the same thing in each. The term is used in 4 chapters of this corpus, most often in Residential Energy Efficiency (IECC 2009), Energy Efficiency (IRC 2009), Definitions (IECC 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? **Air Barrier** — IRC 2009, Definitions: > Material(s) assembled and joined together to provide a barrier to air leakage through the building envelope. An air barrier may be a single material, or a combination of materials. ![Labeled code-term definition diagram: Air Barrier: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/air-barrier/diagram-1344.webp) *How the IRC 2009, IECC 2009 define air barrier, where the wording differs, and which chapters depend on the term.* ## What must be verified before using this guidance? Two of the I-Codes in this corpus define **Air Barrier**, in identical words. | Code | Where it is defined | Definition | | --- | --- | --- | | IRC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | Material(s) assembled and joined together to provide a barrier to air leakage through the building envelope. An air barrier may be a single material, or a combination of materials. | | IECC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/definitions.md) | Material(s) assembled and joined together to provide a barrier to air leakage through the building envelope. An air barrier may be a single material or a combination of materials. | ## Where air barrier is used in the code The term appears in 4 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next. | Chapter | Code | Mentions | | --- | --- | --- | | [Residential Energy Efficiency](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/residential-energy-efficiency.md) | IECC 2009 | 5 | | [Energy Efficiency](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/energy-efficiency.md) | IRC 2009 | 5 | | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/definitions.md) | IECC 2009 | 2 | | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | IRC 2009 | 2 | ### The term in use How the code actually writes about air barrier, quoted from the 2009 text hosted here: > Where required by the code official, an approved party independent from the installer of the insulation shall inspect the air barrier and insulation. — [IECC 2009 §402.4.2.2](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/residential-energy-efficiency.md) > The following shall be caulked, gasketed, weatherstripped or otherwise sealed with an air barrier material, suitable film or solid material. — [IRC 2009, Energy Efficiency](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/energy-efficiency.md) ## The terms air barrier 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 air barrier covers: - **[Building](https://harth.build/resources/glossary/building.md)** — IBC 2009: Any structure used or intended for supporting or sheltering any use or occupancy. ## Air Barrier: 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 | Definitions | | | Read the definition in the adopted IECC | Definitions | | | Re-check the requirement that uses it | Residential Energy Efficiency (IECC 2009) | | | Re-check the requirement that uses it | Energy Efficiency (IRC 2009) | | | Re-check the requirement that uses it | Definitions (IECC 2009) | | | Re-check the requirement that uses it | Definitions (IRC 2009) | | | Confirm the dependent definition | Building | | | 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) - [Building: Building Code Definition](https://harth.build/resources/glossary/building.md) - [Construction Documents: Building Code Definition](https://harth.build/resources/glossary/construction-documents.md) - [Registered Design Professional: Building Code Definition](https://harth.build/resources/glossary/registered-design-professional.md) - [Dwelling Unit: Building Code Definition](https://harth.build/resources/glossary/dwelling-unit.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 air barrier? The International Residential Code (IRC) 2009 defines it in Definitions as: “Material(s) assembled and joined together to provide a barrier to air leakage through the building envelope. An air barrier may be a single material, or a combination of materials.” 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. ### Do the I-Codes define air barrier the same way? In the 2009 editions transcribed here, yes: IRC 2009, IECC 2009 carry the same wording, so the term means the same thing in each. Later editions do diverge on some terms, so confirm against the adopted edition rather than assuming the alignment holds. ### Which parts of the code depend on air barrier? In this corpus the term is used across 4 chapters, led by Residential Energy Efficiency in the IECC 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 an air barrier in a building? In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “Material(s) assembled and joined together to provide a barrier to air leakage through the building envelope. An air barrier may be a single material, or a combination of materials.” It is defined in IRC 2009, IECC 2009. It is not the same as Building, which the IBC 2009 defines separately as “Any structure used or intended for supporting or sheltering any use or occupancy.” 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 purpose of an air barrier? In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “Material(s) assembled and joined together to provide a barrier to air leakage through the building envelope. An air barrier may be a single material, or a combination of materials.” It is defined in IRC 2009, IECC 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. --- - Continue in Harth (open this topic in the Harth agent): https://app.harth.build/agent?context=%2Fresources%2Fglossary%2Fair-barrier%2F - View this page in a browser: https://harth.build/resources/glossary/air-barrier/ - All resources for agents: https://harth.build/llms.txt