---
title: "Thermal comfort and its factors"
subject: "Building Technology"
chapter: 1
key: "semester_6/building_technology:thermal-comfort-factors"
source: https://www.bctengineer.com/q/semester_6/building_technology/thermal-comfort-factors
site: BCT Engineering
---

# Thermal comfort and its factors

Building Technology · Chapter 1: Functional Requirements of Buildings

- Asked in: 2073 Magh; 2070 Magh (asked 2 times)
- Video: [Thermal Comfort in Buildings Explained - HVACR Design](https://www.youtube.com/watch?v=yEWT_XmqCtQ) — The Engineering Mindset
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/thermal-comfort-factors
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-1

## Question

Define thermal comfort. Describe the factors determining thermal comfort.

## Short answer

Thermal comfort is satisfaction with thermal environment. Factors: air temperature, mean radiant temperature, relative humidity, air velocity, clothing insulation, metabolic rate, personal factors.

## Answer

**Thermal comfort** is the state of mind in which a person is satisfied with the thermal environment around him or her, feeling neither hot nor cold.

#### Factors determining thermal comfort
1. **Air temperature**: the dry-bulb temperature of the air; comfort range roughly 21 to 27 °C.
2. **Mean radiant temperature**: heat radiated by walls, floor, ceiling and the sun. A hot ceiling makes people feel warm even in cool air.
3. **Relative humidity**: 30 to 60 % is acceptable. High humidity stops sweat from evaporating, and low humidity dries the skin and throat.
4. **Air velocity**: Air movement increases heat loss by convection and evaporation. 0.1 to 0.5 m/s is comfortable; more than that causes draught.
5. **Clothing insulation (clo)**: Heavy clothes keep heat in.
6. **Metabolic rate / activity (met)**: Hard work produces more heat, so a lower temperature is preferred.
7. **Personal factors**: age, sex, health, body size, acclimatisation, food, and the time spent in the space.
8. **Other**: floor surface temperature, vertical temperature difference, and the outside climate.

Factors 1 to 4 are environmental factors (controlled by the designer), and factors 5 to 7 are personal factors. The combined effect of temperature, humidity and air motion is expressed by **effective temperature**. The designer controls the environmental factors through orientation, insulation, shading, ventilation and, if needed, air conditioning.

## Check yourself

The answer's key points as multiple-choice questions, with the correct option and why.

1. Why does high humidity cause discomfort?
   A. It raises air velocity
   B. It stops sweat from evaporating
   C. It lowers the mean radiant temperature
   D. It makes clothes thinner
   Answer: B. High humidity stops evaporation of sweat, so the body cannot cool. (Key point: Humidity effect)

2. The comfortable air velocity is
   A. 0.1 to 0.5 m/s
   B. 2 to 5 m/s
   C. Zero only
   D. 10 m/s
   Answer: A. More than that causes draught. (Key point: Air velocity)

3. Which is controlled by the designer?
   A. Age and sex
   B. Acclimatisation
   C. Environmental factors such as temperature, radiant temperature, humidity and air velocity
   D. Health of the user
   Answer: C. The first four listed factors are environmental; personal factors are not controlled by the designer. (Key point: Environmental vs personal)

4. Effective temperature combines
   A. Clothing, age and sex
   B. Only dry-bulb and radiant temperature
   C. Metabolism and activity
   D. Temperature, humidity and air motion
   Answer: D. ET expresses the combined effect of temperature, humidity and air motion. (Key point: Effective temperature)

## Related in Building Technology

- [Human thermal comfort and thermal balance](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Ahuman-thermal-comfort-balance) — Building Technology, chapter 1, asked 4×
- [Thermal comfort and its classification](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Athermal-comfort-classification) — Building Technology, chapter 1
- [Achieving thermal comfort, active and passive methods](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aachieve-thermal-comfort-active-passive) — Building Technology, chapter 1
- [Factors affecting thermal performance](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Athermal-perf-factors) — Building Technology, chapter 1
- [Daylight factor, thermal factors, natural ventilation](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Adaylight-thermal-natural-vent) — Building Technology, chapter 1
- [Thermal insulation of walls, doors, windows, roofs](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Athermal-insulation-exposed-walls) — Building Technology, chapter 1, asked 3×

## Related in other subjects

- [Factors affecting human comfort](https://www.bctengineer.com/question.md?key=semester_3%2Fapplied_thermodynamics%3Ahuman-comfort-factors) — Applied Thermodynamics, chapter 4
- [Thermal versus nuclear power plant](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Athermal-vs-nuclear) — Power Plant Design, chapter 1, asked 2×
- [Hydro versus thermal: techno-economic and environmental](https://www.bctengineer.com/question.md?key=semester_8%2Fpower_plant_design%3Ahydro-vs-thermal-techno-economic) — Power Plant Design, chapter 1
- [Conductor sizing factors and armoured cable](https://www.bctengineer.com/question.md?key=semester_6%2Findustrial_power_distribution_and_illumination%3Aconductor-size-factors-armoured) — Industrial Power Distribution and Illumination, chapter 3