# Energy Recovery Ventilation System: Building Code Definition > How the IMC 2009, IECC 2009 define energy recovery ventilation system, where the wording differs, and which chapters depend on the term. - Canonical: https://harth.build/resources/glossary/energy-recovery-ventilation-system/ - 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 | IMC 2009, IECC 2009 (2009 editions transcribed in this corpus) | | Primary source | IMC 2009 Definitions (model text, not a jurisdiction's adopted text) | | Chapters using the term | 5 (counted across the codes hosted here) | | Wording identical across codes | No (compare before citing one code's wording under another) | ## Direct answer Energy recovery ventilation system is a defined term in the International Mechanical Code (IMC) 2009, in Definitions. The code's own words are: “Systems that employ air-to-air heat exchangers to recover energy from or reject energy to exhaust air for the purpose of pre-heating' pre-cooling, humidifying or dehumidifying outdoor ventilation air prior to supplying such air to a space, either directly or as part of an HVAC system.” 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 5 chapters of this corpus, most often in Commercial Energy Efficiency (IECC 2009), Exhaust Systems (IMC 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](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? **Energy Recovery Ventilation System** — IMC 2009, Definitions: > Systems that employ air-to-air heat exchangers to recover energy from or reject energy to exhaust air for the purpose of pre-heating' pre-cooling, humidifying or dehumidifying outdoor ventilation air prior to supplying such air to a space, either directly or as part of an HVAC system. ![Labeled code-term definition diagram: Energy Recovery Ventilation System: Building Code Definition](https://efwwel0vyt9vy5so.public.blob.vercel-storage.com/images/glossary/energy-recovery-ventilation-system/diagram-1344.webp) *How the IMC 2009, IECC 2009 define energy recovery ventilation system, 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 **Energy Recovery Ventilation System**, and the wording is not identical — read the version that governs your question. | Code | Where it is defined | Definition | | --- | --- | --- | | IMC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | Systems that employ air-to-air heat exchangers to recover energy from or reject energy to exhaust air for the purpose of pre-heating' pre-cooling, humidifying or dehumidifying outdoor ventilation air prior to supplying such air to a space, either directly or as part of an HVAC system. | | IECC 2009 | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/definitions.md) | Systems that employ air-to-air heat exchangers to recover energy from exhaust air for the purpose of preheating, precooling, humidifying or dehumidifying outdoor ventilation air prior to supplying the air to a space, either directly or as part of an HVAC system. | ## Where energy recovery ventilation system is used in the code The term appears in 5 chapters of the 2009 I-Codes hosted here. The chapters that lean on it hardest are the ones to read next. | Chapter | Code | Mentions | | --- | --- | --- | | [Commercial Energy Efficiency](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/commercial-energy-efficiency.md) | IECC 2009 | 5 | | [Exhaust Systems](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/exhaust-systems.md) | IMC 2009 | 5 | | [Definitions](https://harth.build/resources/building-codes/us-states/maryland/iecc-2009/definitions.md) | IECC 2009 | 1 | | [Definitions](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/definitions.md) | IMC 2009 | 1 | | [Ventilation](https://harth.build/resources/building-codes/us-states/new-hampshire/imc-2009/ventilation.md) | IMC 2009 | 1 | ## The terms energy recovery ventilation system 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 energy recovery ventilation system covers: - **[Ventilation Air](https://harth.build/resources/glossary/ventilation-air.md)** — IMC 2009: That portion of supply air that comes from the outside (outdoors), plus any recirculated air that has been treated to maintain the desired quality of air within a designated space. - **[Ventilation](https://harth.build/resources/glossary/ventilation.md)** — IBC 2009: The natural or mechanical process of supplying conditioned or unconditioned air to, or removing such air from, any space. - **[System](https://harth.build/resources/glossary/system.md)** — IFC 2009: An assembly of equipment consisting of a tank, container or containers, appurtenances, pumps, compressors and connecting piping. ## Energy Recovery Ventilation System: 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 IMC | Definitions | | | Read the definition in the adopted IECC | Definitions | | | Re-check the requirement that uses it | Commercial Energy Efficiency (IECC 2009) | | | Re-check the requirement that uses it | Exhaust Systems (IMC 2009) | | | Re-check the requirement that uses it | Definitions (IECC 2009) | | | Re-check the requirement that uses it | Definitions (IMC 2009) | | | Confirm the dependent definition | Ventilation Air | | | Confirm the dependent definition | Ventilation | | | Confirm the dependent definition | System | | | 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) - [Ventilation Air: Building Code Definition](https://harth.build/resources/glossary/ventilation-air.md) - [Ventilation: Building Code Definition](https://harth.build/resources/glossary/ventilation.md) - [System: Building Code Definition](https://harth.build/resources/glossary/system.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 energy recovery ventilation system? The International Mechanical Code (IMC) 2009 defines it in Definitions as: “Systems that employ air-to-air heat exchangers to recover energy from or reject energy to exhaust air for the purpose of pre-heating' pre-cooling, humidifying or dehumidifying outdoor ventilation air prior to supplying such air to a space, either directly or as part of an HVAC system.” 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 energy recovery ventilation system the same way? No. 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 energy recovery ventilation system? In this corpus the term is used across 5 chapters, led by Commercial 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 energy recovery ventilation system? In the 2009 I-Codes hosted here it is a defined term rather than a description. The IMC 2009 states, in Definitions: “Systems that employ air-to-air heat exchangers to recover energy from or reject energy to exhaust air for the purpose of pre-heating' pre-cooling, humidifying or dehumidifying outdoor ventilation air prior to supplying such air to a space, either directly or as part of an HVAC system.” It is defined in 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. ### What are the requirements for ventilation in buildings according to the 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 energy recovery ventilation system, which the IMC 2009 defines as “Systems that employ air-to-air heat exchangers to recover energy from or reject energy to exhaust air for the purpose of pre-heating' pre-cooling, humidifying or dehumidifying outdoor ventilation air prior to supplying such air to a space, either directly or as …” — read both before applying either, and confirm the wording in the edition your jurisdiction has adopted. --- - Continue in Harth (open this topic in the Harth agent): https://app.harth.build/agent?context=%2Fresources%2Fglossary%2Fenergy-recovery-ventilation-system%2F - View this page in a browser: https://harth.build/resources/glossary/energy-recovery-ventilation-system/ - All resources for agents: https://harth.build/llms.txt