1. CONDENSATION!
Clive Gibbs

2. WHAT IS CONDENSATION?
Condensation occurs where moist air comes into contact with air, or a surface, which is at a lower temperature. Air contains water vapour in varying quantities, its capacity to do so is related to its temperature - warm air holds more moisture than cold air. When moist air comes into contact with either colder air or a colder surface, the air is unable to retain the same amount of moisture and the water is released to form condensation in the air or on the surface.
Condensation is generally noticeable where it forms on non-absorbent surfaces (i.e. windows or tiles) but it can form on any surface and it may not be noticed until mould growth or rotting of material occurs

3. WHAT IS CONDENSATION? RELATIVE HUMIDITY AIR TEMPERATURE MOISTURE
As the temperature increases the ability of the air to hold more moisture in the form of water vapour increases – therefore the RH decreases

4. CONDENSATION: Normally occurs in the colder months
Starts on the coldest internal surfaces
Most often occurs in rooms of high moisture production
Also in unheated rooms, or rooms with paraffin or butane heaters or unvented tumble dryers
Concentrates in areas where air movement is restricted
Two types:
Surface
Interstitial

5. SURFACE CONDENSATION:
Air contains water
Higher temperature more moisture
Saturation point

6. SURFACE CONDENSATION:
Can occur

7. SURFACE CONDENSATION:
Cold bridging

8. SURFACE CONDENSATION:
Be careful

9. SURFACE CONDENSATION:

10. MOISTURE
The moisture in the air comes from a number of sources within the house.

11. INTERSITIAL CONDENSATION:
Surface condensation and mould growth produce immediately visible problems on the inside surface of buildings. Interstitial condensation is more insidious; before it becomes visible, it can already have caused severe structural damage.
During normal winter occupancy there are greater differences in temperature and vapour pressure from inside to outside
IC occurs in the fabric of the building and is often not identified until some surface damage has occurred

12. INTERSITIAL CONDENSATION:
How?

13. INTERSITIAL CONDENSATION:

14. INTERSITIAL CONDENSATION:

15. PARTIAL FILL:

16. FULL FILL:

17. INTERNAL INSULATION:

18. TIMBER FRAME:

19. EXTERNAL INSULATION:

20. FLAT ROOF:

21. CONCRETE ROOF:

22. DESIGNING:
Balance of factors

23. VAPOUR CONTROL LAYERS:
Used within the construction to control the vapour passing through the fabric of the building
Placed on warm side of insulation
EG Foil backed plasterboard or cavity insulation

24. VAPOUR CONTROL LAYERS:
Partial Fill

25. VAPOUR CONTROL LAYERS:
Partial Fill
Insulation
DEW POINT

26. REFERENCES: BRE Hollis – Surveying Buildings
Digest 54
Digest 163
Digest 329
Digest 380
Understanding Dampness
Tackling Condensation
Hollis – Surveying Buildings
Hoxley – Construction Companion to Building Surveys
Marshall – Understanding Housing Defects
Parnham – Residential Property Appraisal