- 2066 Bhadra (old course) · 16 marks
Achieving thermal comfort, active and passive methods
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.
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.
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
- Select a site and orientation suited to the climate.
- Use a good building form and layout (compact, shaded courtyard).
- Provide a good envelope: insulated walls and roofs, suitable colours, double glazing.
- Provide shading and ventilation.
- 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.
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.
✓ Answer checked by Claude Opus 5.5 (high effort)
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