Correcting the 120-watt assumption: Demographic-aware metabolic rates for energy savings and thermal comfort equity in buildings

Building energy codes universally assume an occupant metabolic heat gain of 120 W/person, embedded in standards such as ASHRAE 90.1 and EN 16798-1. Field and laboratory studies of basal and resting metabolic rates consistently show lower sedentary values (≈ 70–110 W/person), particularly for women and older adults. This study quantifies the energy and comfort impacts of this 120 W/person assumption using 96 annual EnergyPlus simulations across four DOE prototypes and four climates. Demographic-aware metabolic profiles derived from >22,000 occupant records indicate a median load of 93 W/person. Relative to the 120 W default, using this realistic median reduced annual HVAC site energy by 4–10 % without increasing discomfort; adding PMV-based adaptive control raised savings to 12 % and halved gender-based comfort gaps. These simulation results–conservative lower-bound estimates pending empirical validation–highlight both theoretical contributions (demographic-sensitive metabolic modeling, PMV inversion) and practical benefits (energy savings, improved comfort equity, standards-ready defaults). Updating codes and simulation defaults to reflect realistic occupant heat gains could yield substantial efficiency and inclusivity gains in buildings.