The Building Code Council Energy Code TAG on April 4 postponed three competing code proposals about humidification in commercial buildings after lengthy debate among members, mechanical engineers and industry guests.

The TAG postponed the proposals to allow a small work group to draft clearer language and technical guidance. The postponement motion was approved in the meeting with no formal roll-call tally recorded in the transcript.

Panel members and outside presenters spent more than an hour debating whether the 2024 International Energy Conservation Code (IECC) language that restricts steam humidification should be changed to allow higher indoor setpoints and to preserve steam as an option for larger processes. TAG member Larry Andrews argued the health case for higher target humidity in dry climates and urged the TAG to allow higher setpoints and steam humidifiers. "We should be targeting in all these public buildings 50% humidity as best as we can," Andrews said, adding that many studies show fewer infectious microorganisms at higher indoor humidity.

Engineers and other TAG members pushed back on blanket permissions for steam. Dwayne Johnlin and others emphasized that the national model codes moved toward adiabatic (evaporative/atomizing) systems to improve energy performance. Johnlin noted that ASHRAE and IECC language had been thoroughly vetted and that adiabatic approaches can achieve humidification with better efficiency; however, several speakers, including Eric Bedell and Dave Niren, pointed out maintenance, Legionella and lifecycle issues with adiabatic systems in certain applications, especially health care and laboratory settings.

Participants discussed several technical tradeoffs and operational controls TAG members said a revised text should address, including:
- When steam humidification should be allowed (production/process spaces versus general public spaces).
- Distinctions between electric-resistance steam, gas/boiler steam and adiabatic systems and where each is technically appropriate.
- Infection-control and Legionella risk for adiabatic nozzles or pads versus the sanitizing effect of steam.
- Requirements or incentives (credits) that would favor adiabatic systems for efficiency while allowing steam systems when necessary for health, process or reliability.
- Whether energy-recovery ventilators (ERV/HRV) should be required when humidification above the baseline is used; several TAG members favored an HRV/ERV requirement in cold climates.

TAG members agreed on next steps: a work group led by volunteers, including several mechanical engineers and TAG members, will draft recommended language before the TAG's next substantive meeting. The group should address definitions, controls, allowable humidification methods, maintenance requirements for adiabatic systems, and whether a credit table (C406-style) or prescriptive exception is the best mechanism to balance energy and health outcomes. The TAG intends to reconvene the humidification discussion during the next meeting cycle so the draft language can be considered and the group's recommended edits circulated in advance.

Why this matters: the TAG is balancing public-health arguments for higher indoor humidity in dry climates with energy-efficiency and infection-control concerns. The decision to form a focused work group reflects technical complexity and the desire to avoid a one-size-fits-all policy.

Speakers (selected)
- Larry Andrews — TAG member, Building Code Council (government)
- Eric Bedell — TAG member, Building Code Council (government)
- Dwayne Johnlin — TAG member, Building Code Council (government)
- Dave Niren — Engineering manager, Hermanson Company (business)
- Nathan Miller — TAG member, Building Code Council (government)
- Greg Johnson — TAG member, Building Code Council (government)
- Patrick Hayes — architect/developer (business)

Authorities
- IECC 2024 (referenced repeatedly in discussion)

Actions
- Postponed: Motion to postpone three humidification proposals and form a work group (no formal roll-call totals recorded in transcript). Outcome: passed (motion carried). Notes: TAG asked work group to produce draft language for next meeting.

Clarifying details
- Proposals affected: referenced by proposal numbers during meeting; TAG consolidated discussion for proposals addressing similar humidification topics.
- Key technical debate: steam (electric or gas) vs adiabatic humidification, Legionella risk, controls, and required ERV/HRV ventilation when humidifying.

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