Energy code panel delays humidification rule changes after debate over steam, adiabatic systems

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…