# Sunroom: Building Code Definition

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

- Canonical: https://harth.build/resources/glossary/sunroom/
- 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 | 10 (counted across the codes hosted here) |
| Wording identical across codes | Yes (compare before citing one code's wording under another) |

## Direct answer

Sunroom is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “A one-story structure attached to a dwelling with a glazing area in excess of 40 percent of the gross area of the structure's exterior walls and roof.” The IECC 2009 carries the same definition word for word, so the term means the same thing in each. The term is used in 10 chapters of this corpus, most often in Building Planning (IRC 2009), Interior Environment (IBC 2009), Residential Energy Efficiency (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?

**Sunroom** — IRC 2009, Definitions:

> A one-story structure attached to a dwelling with a glazing area in excess of 40 percent of the gross area of the structure's exterior walls and roof.

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

*How the IRC 2009, IECC 2009 define sunroom, 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 **Sunroom**, 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) | A one-story structure attached to a dwelling with a glazing area in excess of 40 percent of the gross area of the structure's exterior walls and roof. |
| IECC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/definitions.md) | A one-story structure attached to a dwelling with a glazing area in excess of 40 percent of the gross area of the structure's exterior walls and roof. |

## Where sunroom is used in the code

The term appears in 10 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next.

| Chapter | Code | Mentions |
| --- | --- | --- |
| [Building Planning](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/building-planning.md) | IRC 2009 | 16 |
| [Interior Environment](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/interior-environment.md) | IBC 2009 | 13 |
| [Residential Energy Efficiency](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/residential-energy-efficiency.md) | IECC 2009 | 8 |
| [Energy Efficiency](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/energy-efficiency.md) | IRC 2009 | 8 |
| [Ventilation](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/ventilation.md) | IMC 2009 | 4 |
| [Definitions](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/definitions.md) | IBC 2009 | 2 |
| [Definitions](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/definitions.md) | IECC 2009 | 2 |
| [Glass and Glazing](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/glass-and-glazing.md) | IBC 2009 | 1 |
| [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | IRC 2009 | 1 |
| [Power and Lighting Distribution](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/power-and-lighting-distribution.md) | IRC 2009 | 1 |

### The term in use

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

> Required glazed openings shall be permitted to open into sunroom additions or patio covers that abut a street, yard or court if in excess of 40 percent of the exterior sunroom walls are open, or are enclosed only by insect screening, and the ceiling height of the sun-room is not less than 7 feet (2134 mm).

— [IRC 2009 §R303.7.1](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/building-planning.md)

> New wall (s) separating a sunroom from conditioned space shall meet the building thermal envelope requirements.

— [IECC 2009 §402.2.11](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/residential-energy-efficiency.md)


## The terms sunroom is built out of

The definition above leans on 4 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what sunroom covers:

- **[Glazing Area](https://harth.build/resources/glossary/glazing-area.md)** — IRC 2009: The interior surface area of all glazed fenestration, including the area of sash, curbing or other framing elements, that enclose conditioned space.
- **[Structure](https://harth.build/resources/glossary/structure.md)** — IPC 2009: That which is built or constructed or a portion thereof.
- **[Dwelling](https://harth.build/resources/glossary/dwelling.md)** — IBC 2009: A building that contains one or two dwelling units used, intended or designed to be used, rented, leased, let or hired out to be occupied for living purposes.
- **[Story](https://harth.build/resources/glossary/story.md)** — IBC 2009: That portion ofa building included between the upper surface of a floor and the upper surface of the floor or roof next above (also see "Basement," "Mezzanine" and Section 502.1).

## Sunroom: 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 | Building Planning (IRC 2009) | |
| Re-check the requirement that uses it | Interior Environment (IBC 2009) | |
| Re-check the requirement that uses it | Residential Energy Efficiency (IECC 2009) | |
| Re-check the requirement that uses it | Energy Efficiency (IRC 2009) | |
| Confirm the dependent definition | Glazing Area | |
| Confirm the dependent definition | Structure | |
| Confirm the dependent definition | Dwelling | |
| 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)
- [Glazing Area: Building Code Definition](https://harth.build/resources/glossary/glazing-area.md)
- [Structure: Building Code Definition](https://harth.build/resources/glossary/structure.md)
- [Dwelling: Building Code Definition](https://harth.build/resources/glossary/dwelling.md)
- [Story: Building Code Definition](https://harth.build/resources/glossary/story.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 sunroom?

The International Residential Code (IRC) 2009 defines it in Definitions as: “A one-story structure attached to a dwelling with a glazing area in excess of 40 percent of the gross area of the structure's exterior walls and roof.” 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 sunroom 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 sunroom?

In this corpus the term is used across 10 chapters, led by Building Planning 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 the definition of a sunroom according to the Florida building code?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “A one-story structure attached to a dwelling with a glazing area in excess of 40 percent of the gross area of the structure's exterior walls and roof.” 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 considered a sunroom?

In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “A one-story structure attached to a dwelling with a glazing area in excess of 40 percent of the gross area of the structure's exterior walls and roof.” 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.

### What does IRC mean in 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 sunroom, which the IRC 2009 defines as “A one-story structure attached to a dwelling with a glazing area in excess of 40 percent of the gross area of the structure's exterior walls and roof.” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted.

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