---
title: "Achieving thermal comfort, active and passive methods"
subject: "Building Technology"
chapter: 1
key: "semester_6/building_technology:achieve-thermal-comfort-active-passive"
source: https://www.bctengineer.com/q/semester_6/building_technology/achieve-thermal-comfort-active-passive
site: BCT Engineering
---

# Achieving thermal comfort, active and passive methods

Building Technology · Chapter 1: Functional Requirements of Buildings

- Asked in: 2066 Bhadra (old course), 16 marks
- Video: [Green Building | Active and Passive Techniques](https://www.youtube.com/watch?v=nJqfY0yI89w) — معرض الأزهر للتطبيقات الهندسية
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/achieve-thermal-comfort-active-passive
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-1

## Question

Discuss about thermal comfort in building. How can we achieve thermal comfort? Explain about active and passive methods for heating and cooling. Support your answer with neat and clean sketches.

## Short answer

Thermal comfort depends on air temperature, humidity, air speed, clothing, and activity. Achieved by site orientation, insulated envelope, shading, ventilation, then active systems. Passive methods: direct gain, Trombe wall, cross ventilation, evaporative cooling. Active methods: heaters, heat pumps, air conditioning. Use passive first to reduce loads, then active for remainder.

## Answer

**Thermal comfort** is the state of mind in which a person is satisfied with the thermal environment. It depends on air temperature, radiant temperature, humidity, air speed, clothing and activity. The comfort range is about 21 to 27 °C with 30 to 60 % relative humidity.

#### How to achieve thermal comfort
1. Select a **site and orientation** suited to the climate.
2. Use a good **building form and layout** (compact, shaded courtyard).
3. Provide a good **envelope**: insulated walls and roofs, suitable colours, double glazing.
4. Provide **shading** and **ventilation**.
5. Use **heating or cooling** devices where passive means are not sufficient.

#### Passive methods
Use natural energy flows without mechanical equipment.
- **Passive heating**: direct gain (south windows with thermal mass), Trombe wall, sunspace, insulation, compact form.
- **Passive cooling**: shading by chhajja, trees and louvres; cross and stack ventilation; courtyards and wind catchers; evaporative cooling with ponds and plants; earth-contact cooling; night ventilation; light-coloured, insulated roofs.

```text
 Passive heating (winter)      Passive cooling (summer)
 sun-> [glass]|dark wall       shade ^  hot air out (high)
        warm air to room       cool air in (low) <- shaded yard
```

#### Active methods
Use energy-consuming equipment.
- **Active heating**: electric heaters, heat pumps, boilers with radiators, solar water or air collectors with pumps, gas or biomass heaters.
- **Active cooling**: fans, evaporative (desert) coolers, split and central air conditioning, chillers.
- **Controls**: thermostats, timers and sensors.

#### Comparison
| Point | Passive | Active |
|---|---|---|
| Energy | None or very little | Electricity or fuel |
| Cost | Low running cost | High running cost |
| Control | Limited | Precise |
| Maintenance | Low | High |

Best practice is to use passive measures first to reduce loads, and add active systems only to cover the remainder.

## Check yourself

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

1. The comfort range given is about:
   A. 15-18 C with 80 % RH
   B. 21-27 C with 30-60 % RH
   C. 30-35 C with 10 % RH
   D. 10-15 C with 50 % RH
   Answer: B. Comfort is about 21 to 27 C with 30 to 60 % relative humidity. (Key point: Comfort range)

2. What defines a passive method?
   A. Uses natural energy flows without mechanical equipment
   B. Uses electric heaters
   C. Needs thermostats and sensors
   D. Uses chillers
   Answer: A. Passive methods rely on design (orientation, shading, mass) not energy-consuming equipment. (Key point: Passive vs active)

3. Which is a passive heating technique?
   A. Split air conditioner
   B. Trombe wall
   C. Boiler with radiators
   D. Heat pump
   Answer: B. A Trombe wall, direct gain and sunspace are passive; the others are active. (Key point: Passive heating)

4. What is the recommended order of approach?
   A. Active systems first, passive to follow
   B. Only active systems
   C. Passive measures first to cut loads, then active for the remainder
   D. Only insulation
   Answer: C. Passive measures reduce loads, and active systems cover what is left. (Key point: Best practice)

## 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 factors](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Athermal-comfort-factors) — Building Technology, chapter 1, asked 2×
- [Thermal comfort and its classification](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Athermal-comfort-classification) — Building Technology, chapter 1
- [Active and passive solar control](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Aactive-passive-solar) — Building Technology, chapter 1
- [Passive solar design and building layout](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Apassive-solar-design) — Building Technology, chapter 1
- [Thermal performance and building geometry](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Athermal-perf-geometry) — Building Technology, chapter 1

## Related in other subjects

- [Heating and cooling time constants](https://www.bctengineer.com/question.md?key=semester_5%2Felectric_machine_design%3Aheating-cooling-time-constants) — Electric Machine Design, chapter 2, asked 3×
- [Transformer heating and cooling time constants (25°C/37.5°C)](https://www.bctengineer.com/question.md?key=semester_5%2Felectric_machine_design%3Atransformer-heating-cooling-constants) — Electric Machine Design, chapter 2, asked 3×
- [Transformer heating and cooling time constants (25°C/40°C)](https://www.bctengineer.com/question.md?key=semester_5%2Felectric_machine_design%3Atransformer-cooling-constant-45c) — Electric Machine Design, chapter 2, asked 3×
- [Active vs passive; non-inverting (s+8)/(s+2)](https://www.bctengineer.com/question.md?key=semester_5%2Ffilter_design%3Aactive-passive-difference-noninverting) — Filter Design, chapter 6, asked 5×