Adaptive Comfort Models: What Indian Climate Data Actually ShowsPREVIEW

Indian researchers built comfort models
using 9-month heat data. Buildings still
use the 3-month American standard. The
science diverged 20 years ago. The
buildings have not caught up.

Adaptive comfort models are derived from
long-term field studies in real buildings
where occupants live through continuous
heat for months at a time. Unlike
laboratory studies, field research
captures physiological acclimation: the
body's ability to recalibrate comfort
temperature setpoints when exposed to
sustained thermal conditions.

IIT Bombay and IIT Kharagpur conducted the
foundational adaptive comfort field study
for India. Over 3 years, researchers
measured thermal comfort votes from office
occupants in Mumbai and Pune through full
annual cycles: March heat, monsoon cooling
relief, and the return to heat in
post-monsoon seasons. The resulting
adaptive comfort model, published in
Building and Environment (2015), specified
comfort temperatures 1.5 to 2.5 degrees
Celsius higher than ASHRAE Standard 55 for
the same indoor conditions.

The mechanism is physiological
acclimation. After 2 to 3 weeks of
sustained heat exposure, a person's
thermoregulatory setpoint shifts upward.
The metabolic rate baseline increases.
Sudomotor activity (sweat gland
sensitivity) adjusts. By 9 weeks of
continuous heat, the adaptation is
substantial. An Indian office worker in
August, acclimated to 3 months of
March-to-May heat, has a fundamentally
different thermal comfort expectation than
a July office worker in Boston, acclimated
to a 1-month heat ramp.

Buildings designed using ASHRAE 55 lock in
non-adaptive setpoints: 21.5°C year-round
comfort. This conflicts with occupant
biology. Worse, it consumes extra energy
to maintain a comfort standard that
occupants will eventually find
uncomfortably cold. A retrofit that shifts
from mechanical HVAC-only to Biothermal
Microconditioning lets the system adapt as
occupants acclimate. Person-level
evapotranspiration from areca palm
clusters, combined with adaptive thermal
mass in Terrapods, creates a system that
cools in response to occupant thermal
comfort, not just air temperature
setpoint.