Advice & Guidance
Condensation
Condensation is essentially the release of water that occurs when air is cooled to its ‘dew point' temperature and can carry less moisture as vapour.
Water vapour
may condense indoors when warm,
damp air comes into contact with colder building components such as
windows or
uninsulated roofs.
Historically, generous ventilation helped the moisture present in buildings to escape via openable windows, air grilles, vents and loose-fitting doors. However the balance of the internal environment can easily be upset leading to excess condensation and perhaps mould and timber decay.
This is often the result of additional moisture being driven into the atmosphere from sources such as flueless bottled gas heaters or from hot water urns and kettles.
Condensation also can arise when ventilation is reduced by over-zealous draught-proofing or the blocking of air bricks. Additionally, it may occur where the ‘breathability' of solid masonry walls is compromised by external cement render or an internal vapour barrier such as impermeable paint.
The best way to tackle condensation is to reduce the amount of water being released into the atmosphere and to improve ventilation. In particular, you should ensure that ceiling and floor voids and redundant chimneys are well ventilated.
Increasing the level of heating can also help to maintain surfaces above dew point, especially if the heating is run constantly at a low level rather than intermittently.
It is also
worthwhile lagging cold pipes to prevent surface condensation. Contrary
to popular belief dehumidifiers are
probably not the answer for most places of worship as they are of limited
benefit
when spaces are cold and humid (although they can reduce condensation
effectively when spaces are warm and damp).
Action point: Make sure that you open windows and doors to allow air movement through your building.
This is especially worthwhile on warm dry summer days but is still beneficial in the winter, as the lower external vapour pressure will tend to draw out moisture.
You many need to consider fitting bird guards to protect opening hoppers and installing a bird screen to prevent birds entering the building whilst the main door is open.
Action point: If window hoppers have seized or stopped working consider having them repaired and brought back into use again. Alternatively, if there are no opening windows in your place of worship seek advice about how to improve ventilation from your professional adviser.
Action point: Consider
whether you can make changes to your heating regime to help keep
surface
temperatures above dew point.
Further information
SPAB (1992) SPAB Technical Pamphlet 8: The Control of Damp in Old Buildings, SPAB
SPAB (1987) SPAB Information Sheet 4: The Need for Old Buildings to Breathe, SPAB
Trotman P, Sanders, C and Harrison, H (2004) Understanding Dampness: Effects, Causes, Diagnosis and Remedies, BRE
Burkinshaw, R and Parrett, M (2003) Diagnosing Damp, RICS
© SPAB 2010
