Beyond the classic thermoneutral zone: Including thermal comfort

Area of Science:

• Human physiology
• Biophysics
• Environmental health

Background:

• The thermoneutral zone (TNZ) is defined by ambient temperatures allowing core temperature regulation via dry heat loss.
• Maintaining core temperature requires balancing metabolic heat production with heat loss to the environment.

Purpose of the Study:

• To investigate combinations of core and skin temperatures satisfying TNZ biophysical requirements in humans.
• To analyze the impact of insulation changes and thermal comfort on the TNZ.
• To re-evaluate the definition of the thermoneutral zone based on biophysical principles.

Main Methods:

• Development of a biophysical model to calculate human body heat transport.
• The model accounts for metabolic heat production, tissue insulation, and blood flow distribution.
• Heat transport is equated to heat loss to the environment under varying thermal conditions.

Main Results:

• The steady-state ambient temperature range of the TNZ does not inherently guarantee thermal balance at basal metabolic rate.
• Specific combinations of core, skin, and ambient temperatures may necessitate increased heat production or loss.
• The ambient temperature range for thermal comfort is narrower than the TNZ.

Conclusions:

• The current definition of the thermoneutral zone may require reformulation.
• Thermal behavior might be initiated prior to reaching TNZ boundaries due to thermal comfort considerations.
• Biophysical modeling provides a more nuanced understanding of human thermal regulation.