---
title: "Factors affecting thermal performance"
subject: "Building Technology"
chapter: 1
key: "semester_6/building_technology:thermal-perf-factors"
source: https://www.bctengineer.com/q/semester_6/building_technology/thermal-perf-factors
site: BCT Engineering
---

# Factors affecting thermal performance

Building Technology · Chapter 1: Functional Requirements of Buildings

- Asked in: 2080 Chaitra, 4 marks
- Video: [Factors affecting thermal performance of buildings](https://www.youtube.com/watch?v=GtXWjALwTkM) — Rajathi Ram
- Answer checked by Claude Opus 5.5 (high effort) on 2026-10-14
- Page: https://www.bctengineer.com/q/semester_6/building_technology/thermal-perf-factors
- Whole chapter: https://www.bctengineer.com/md/semester_6/building_technology/chapter-1

## Question

Explain four basic factors affecting thermal performance of a building.

## Short answer

Four basic factors affecting thermal performance: climate and site (temperature, humidity, solar radiation, wind); orientation and building form (geometry, solar gain, exposed surface area); building envelope materials and construction (conductivity, thermal mass, reflectivity, U-value); openings and ventilation (window size, position, shading, air leakage).

## Answer

The thermal performance of a building is its capacity to keep the interior comfortable by controlling heat flow. Four basic factors are:

1. **Climate and site**: Air temperature, humidity, solar radiation, wind and rainfall decide the heating or cooling load. Site features such as slope, trees and neighbouring buildings change local exposure.
2. **Orientation and building form (geometry)**: The direction of the building and its shape decide the solar gain and the exposed surface area. A compact form with long axis east-west reduces heat exchange.
3. **Building envelope materials and construction**: Conductivity, thickness, thermal mass, colour and reflectivity of walls, roof, floor, and glass. Resistance is $R = t/k$ and transmittance $U = 1/R_{total}$. Low U-value gives better performance. Heavy materials give time lag.
4. **Openings and ventilation**: The size, position and shading of windows control solar gain, daylight and air movement. Air leakage and natural ventilation affect both heat and humidity.

Other factors are internal heat gains (occupants, lights, appliances) and the use pattern.

## Check yourself

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

1. A compact form with long axis east-west
   A. Reduces heat exchange
   B. Increases exposed surface
   C. Blocks all light
   D. Raises U-value
   Answer: A. Compact form reduces exposed area and solar gain. (Key point: Orientation and form)

2. Better thermal performance is shown by
   A. High U-value
   B. Low U-value
   C. Low R
   D. High conductivity and thin wall
   Answer: B. U = 1/R total. (Key point: U-value)

3. Window size, position and shading control
   A. Only structure strength
   B. Only cost
   C. Solar gain, daylight and air movement
   D. Only sound
   Answer: C. Openings affect heat, light and ventilation. (Key point: Openings)

4. Heavy materials give
   A. Faster heat transfer
   B. No effect
   C. Higher U-value
   D. Time lag
   Answer: D. They delay heat flow. (Key point: Time lag)

## Related in Building Technology

- [Thermal performance and building geometry](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Athermal-perf-geometry) — 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 performance, transmittance of composite wall](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Athermal-composite-wall-062ba) — Building Technology, chapter 1
- [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×
- [Factors affecting foundation design, improving bearing capacity](https://www.bctengineer.com/question.md?key=semester_6%2Fbuilding_technology%3Afactors-design-improve-bc) — Building Technology, chapter 2
- [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×

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