# Conditioned Space: Building Code Definition > How the IRC 2009, IMC 2009, IECC 2009 define conditioned space, where the wording differs, and which chapters depend on the term. - Canonical: https://harth.build/resources/glossary/conditioned-space/ - 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, IMC 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 | 12 (counted across the codes hosted here) | | Wording identical across codes | No (compare before citing one code's wording under another) | ## Direct answer Conditioned space is a defined term in the International Residential Code (IRC) 2009, in Definitions. The code's own words are: “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 mechanical purposes, an area, room or space being heated or …” The IMC 2009, IECC 2009 define 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 12 chapters of this corpus, most often in Residential Energy Efficiency (IECC 2009), Definitions (IECC 2009), Energy Efficiency (IRC 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](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? **Conditioned Space** — IRC 2009, Definitions: > 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 mechanical purposes, an area, room or space being heated or cooled by any equipment or appliance. ![Labeled code-term definition diagram: Conditioned Space: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/conditioned-space/diagram-1344.webp) *How the IRC 2009, IMC 2009, IECC 2009 define conditioned space, where the wording differs, and which chapters depend on the term.* ## What must be verified before using this guidance? Three of the I-Codes in this corpus define **Conditioned Space**, and the wording is not identical — read the version that governs your question. | Code | Where it is defined | Definition | | --- | --- | --- | | IRC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | 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 mechanical purposes, an area, room or space being heated or cooled by any equipment or appliance. | | IMC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | An area, room or space being heated or cooled by any equipment or appliance. | | IECC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/definitions.md) | An area or room within a building being heated or cooled, containing uninsulated ducts, or with a fixed opening directly into an adjacent conditioned space. | ## Where conditioned space is used in the code The term appears in 12 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 | 21 | | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/definitions.md) | IECC 2009 | 18 | | [Energy Efficiency](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/energy-efficiency.md) | IRC 2009 | 17 | | [Administration](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/administration.md) | IECC 2009 | 12 | | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/definitions.md) | IRC 2009 | 12 | | [Commercial Energy Efficiency](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/commercial-energy-efficiency.md) | IECC 2009 | 10 | | [Fuel Gas](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/fuel-gas.md) | IRC 2009 | 10 | | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | IMC 2009 | 4 | | [Exhaust Systems](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/exhaust-systems.md) | IMC 2009 | 2 | | [Duct Systems](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/duct-systems.md) | IRC 2009 | 2 | | [Water Supply and Distribution](https://harth.build/resources/building-codes/us-states/maryland/irc-2009/water-supply-and-distribution.md) | IRC 2009 | 2 | | [Interior Environment](https://harth.build/resources/building-codes/us-states/maryland/ibc-2009/interior-environment.md) | IBC 2009 | 1 | ### The term in use How the code actually writes about conditioned space, quoted from the 2009 text hosted here: > 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) > Any nonconditioned space that is altered to become conditioned space shall be required to be brought into full compliance with this code. — [IECC 2009 §101.4.5](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/administration.md) > A door that separates conditioned space from the exterior shall be protected with an enclosed vestibule, with all doors opening into and out of the vestibule equipped with self-closing devices. — [IECC 2009 §502.4.7](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/commercial-energy-efficiency.md) ## Conditioned Space compared with Conditioned Area These two are the closest pair in the 2009 I-Codes: about 48 per cent of their defining words are the same. The code states both and compares neither, so the difference is worth naming. | | Wording unique to it | | --- | --- | | **Conditioned Space** (IRC 2009) | energy, purposes, space, equipmentor, 50, io, 85, 29, communicates, mechanical, room, being | | [Conditioned Area](https://harth.build/resources/glossary/conditioned-area.md) (IRC 2009) | appliances, 68, 20, 80, 27, fixed, opening, adjacent | Everything else in the two definitions is shared. If a project turns on which of the two applies, those words are the whole of the test — and a local amendment that edits one of them without editing the other moves the boundary between conditioned space and conditioned area. ## The terms conditioned space is built out of The definition above leans on 3 other defined terms. Each carries its own code definition, and a local amendment to any of them changes what conditioned space covers: - **[Equipment](https://harth.build/resources/glossary/equipment.md)** — IRC 2009: All piping, ducts, vents, control devices and other components of systems other than appliances that are permanently installed and integrated to provide control of environmental conditions for buildings. - **[Appliance](https://harth.build/resources/glossary/appliance.md)** — IRC 2009: Utilization equipment, normally built in standardized sizes or types, that is installed or connected as a unit to perform one or more functions such as clothes washing, air conditioning, food mixing, deep frying, etc. - **[Building](https://harth.build/resources/glossary/building.md)** — IBC 2009: Any structure used or intended for supporting or sheltering any use or occupancy. ## Conditioned Space: 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 IMC | 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 | Definitions (IECC 2009) | | | Re-check the requirement that uses it | Energy Efficiency (IRC 2009) | | | Re-check the requirement that uses it | Administration (IECC 2009) | | | Confirm the dependent definition | Equipment | | | Confirm the dependent definition | Appliance | | | 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) - [Equipment: Building Code Definition](https://harth.build/resources/glossary/equipment.md) - [Appliance: Building Code Definition](https://harth.build/resources/glossary/appliance.md) - [Building: Building Code Definition](https://harth.build/resources/glossary/building.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 conditioned space? The International Residential Code (IRC) 2009 defines it in Definitions 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 mechanical purposes, an area, room or space being heated or cooled by any equipment or appliance.” 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 conditioned space the same way? No. IRC 2009, IMC 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 conditioned space? In this corpus the term is used across 12 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 considered conditioned space 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: “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 mechanical purposes, an area, room or space being heated or …” It is defined in IRC 2009, IMC 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 definition of a conditioned space? In the 2009 I-Codes hosted here it is a defined term rather than a description. The IRC 2009 states, in Definitions: “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 mechanical purposes, an area, room or space being heated or …” It is defined in IRC 2009, IMC 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%2Fconditioned-space%2F - View this page in a browser: https://harth.build/resources/glossary/conditioned-space/ - All resources for agents: https://harth.build/llms.txt