Building Services Engineering 5th Edition Handbook

10 Condensation in buildings
Learning objectives
Study of this chapter will enable the reader to:
1. identify the moisture content of humid air by its vapour pressure;
2. understand dew-point temperature;
3. identify the sources of moisture within a building;
4. understand the flow and storage characteristics of moisture flows found in habitable
building;
5. explain the causes of condensation;
6. discuss the damage which can be caused by condensation;
7. calculate vapour diffusion resistance;
8. calculate vapour flow;
9. calculate air vapour pressure;
10. calculate air dew-point temperature;
11. understand atmospheric pressure terms;
12. use the e x calculator function;
13. use the log e calculator function;
14. be able to convert from e x to log e forms;
15. calculate and draw thermal temperature gradients through structures;
16. calculate and draw dew-point temperature gradients through structures;
17. identify condensation zones within structures;
18. discuss surface and interstitial condensation;
19. understand where to install thermal insulation and vapour barriers in relation to
condensation risk and thermal and structural integrity requirements.
Key terms and concepts
atmospheric pressure 240; change of phase 240; condensation 240; dew-point 240; dewpoint
temperature gradient 251; diffusion 242; dry- and wet-bulb air temperatures 240;
exponential and logarithmic functions 244; moisture flow 242; moisture production 240;