ERVs are great tools, but IMC 513 makes one thing clear: you can't recover energy from every airstream. This section is really about where ERVs are allowed, where they are prohibited, and how to document cross-leakage and access.
Plain English:
513.1 general
ERV systems must be installed per IMC 513.
If ERV is required for energy conservation, it must also comply with the International Energy Conservation Code (IECC).
Ducted HRVs must be listed/labeled to UL 1812.
Nonducted HRVs must be listed/labeled to UL 1815.
513.2 prohibited applications
ERV systems cannot be used on:
Hazardous exhaust systems (IMC 509)
Dust/stock/refuse systems conveying explosive or flammable vapors, fumes, or dust
Smoke control systems (IMC 512)
Commercial kitchen exhaust serving Type I hoods
Clothes dryer exhaust systems (IMC 504)
Exception: sensible-only recovery using coil-type heat exchangers is not limited by this prohibition.
513.3 access
Provide access to the heat exchanger and other components for service, maintenance, repair, or replacement.
513.4 recirculated air / cross-leakage
Air in an ERV is not considered recirculated air if the system is constructed to limit cross-leakage between airstreams to less than 10% of total design airflow.
On Plans: Why it matters
Most ERV redlines are predictable: applying total energy recovery to prohibited exhaust streams, showing an ERV with no listing basis, or failing to address cross-leakage and maintenance access on the plans.
Code Path: Where to show it
M-001: "IMC 513 ERV" note with listing basis, prohibited airstream limitations, and <10% cross-leakage criterion where applicable.
Schedules: unit type, listing standard, sensible-only vs total recovery, and cross-leakage basis.
Plans/details: service clearances and access path to exchanger/core and filters.
Check: Do
Verify the exhaust/source airstream is actually eligible for ERV before selecting the unit.
Call out listing standard and cross-leakage basis on the schedule.
Review Risk: Don't
Don't connect ERVs to hazardous exhaust, Type I kitchen exhaust, smoke control, or dryer exhaust.
Field Tip:
Ask one question before you put an ERV on a job: "What exact exhaust airstream am I recovering from?" If the answer touches hazardous, grease, smoke control, dust/explosive contaminants, or dryer exhaust, stop and re-check IMC 513.2 before modeling anything.
Masterbuild QA Lens
IMC 513 review starts with eligibility, not equipment selection: confirm the exhaust airstream feeding the ERV is not hazardous exhaust (509), dust/stock/refuse conveying explosive or flammable material, smoke control (512), Type I kitchen exhaust, or clothes dryer exhaust - the sensible-only coil-type exception is the only carve-out.
Confirm the unit is listed to UL 1812 (ducted) or UL 1815 (nonducted), that service access to the heat exchanger and other components is shown on the plans, and that cross-leakage between airstreams is documented at less than 10% of total design airflow so the air is not counted as recirculated. An ERV connected to a prohibited airstream is a 513.2 violation regardless of how well the unit itself is specified.
Drawing / Submittal Check
For energy recovery ventilation (IMC 513): the drawings must show the ERV/HRV unit location, the supply and exhaust connections, the defrost method (for cold climates), the controls sequence including any economizer lockout, and the outdoor air rate it provides. The ERV performance must be shown in the schedule at the actual entering conditions - sensible and total effectiveness. Confirm the unit is listed and the AHJ accepts the listing.
Common Review Risk
Energy recovery ventilation systems that are specified but not commissioned are a common building performance problem. The ERV may be installed and running, but if the supply and exhaust are connected in reverse, it is wasting energy instead of recovering it. Confirm the commissioning protocol includes a flow measurement to verify supply and exhaust connections. A reversed ERV is impossible to detect without airflow measurement.
When To Escalate
Escalate when the energy recovery ventilation system serves a building with unusual exhaust streams - cooking exhaust, chemical exhaust, or high-humidity exhaust - that could contaminate the supply air if cross-leakage occurs. ERV cross-leakage in a building with hazardous exhaust is a health and safety problem. Confirm the leakage classification of the selected ERV core is appropriate for the exhaust type before specifying the unit.
Kitchen Exhaust Coordination
For kitchen exhaust, tie the hood schedule, appliance lineup, grease duct route, cleanouts, fan discharge, fire suppression interface, and make-up air strategy into one reviewable story.
Special Exhaust Coordination
For specialty exhaust, start with the contaminant and source. Then confirm capture method, duct material, routing, discharge, separation, controls, and whether another consultant or AHJ review is required.