Building Code Glossary
Insulating Sheathing: Building Code Definition
How the IRC 2009, IECC 2009 define insulating sheathing, 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
Insulating sheathing is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “An insulating board having a minimum thermal resistance of R-2 of the core material.” The IECC 2009 words it differently, in Definitions: “An insulating board with a core material having a minimum R-value of R-2.” The IECC 2009 defines the same term with different wording, so the controlling text depends on which code governs the question in front of you — the comparison below sets the versions side by side. 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.
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?
Insulating Sheathing — IRC 2009, Definitions:
An insulating board having a minimum thermal resistance of R-2 of the core material.
What must be verified before using this guidance?
Two of the I-Codes in this corpus define Insulating Sheathing, and the wording is not identical — read the version that governs your question.
| Code | Where it is defined | Definition |
|---|---|---|
| IRC 2009 | Definitions | An insulating board having a minimum thermal resistance of R-2 of the core material. |
| IECC 2009 | Definitions | An insulating board with a core material having a minimum R-value of R-2. |
Where insulating sheathing 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 | IECC 2009 | 2 |
| Energy Efficiency | IRC 2009 | 2 |
| Definitions | IECC 2009 | 1 |
| Definitions | IRC 2009 | 1 |
The term in use
How the code actually writes about insulating sheathing, quoted from the 2009 text hosted here:
Insulation material used in layers, such as framing cavity insulation and insulating sheathing, shall be summed to compute the component R-value.
Insulating Sheathing: 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 | |
| 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) | |
| 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
- Building: Building Code Definition
- Construction Documents: Building Code Definition
- Registered Design Professional: Building Code Definition
- Dwelling Unit: 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 insulating sheathing?
The International Residential Code (IRC) 2009 defines it in Definitions as: “An insulating board having a minimum thermal resistance of R-2 of the core material.” 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 insulating sheathing the same way?
No. IRC 2009, IECC 2009 all define the term, but the wording is not identical, and a difference in wording can change which requirements are triggered. The comparison table above sets the versions side by side so you can read the one that governs your question.
Which parts of the code depend on insulating sheathing?
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.
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