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Current Bulletin
“Stave off decay by daily care”
William Morris 1877
Welcome to May e-bulletin. Every month we will be sending you a few top maintenance tips to help you care for your historic building. This month we thought we'd talk about 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, grilles 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 places of worship as they only really work effectively in small, self-contained spaces and are of limited benefit when spaces are cold and humid.
Things
to do...
- 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 can still be beneficial in the winter, as the lower external vapour pressure will tend to draw out moisture.
- If window hoppers have seized or stopped working consider having them repaired and brought back into use again.
- If there are no opening windows in your place of worship seek advice about how to improve ventilation from your professional adviser.
- Consider whether you can make changes to your heating regime to help keep surface temperatures above dew point.
Further information
SPAB (1992) Technical Pamphlet 8: The Control of Damp in Old Buildings.
SPAB (1987) Information Sheet 4: The Need for Old Buildings to Breathe.
Burkinshaw, R and Parrett, M (2003) Diagnosing Damp, RICS.
Need more help?
If you have any questions about maintenance or repair issues contact our Technical Helpline for advice and guidance. This service is normally available from Monday to Thursday between 9.30am and 12.30pm on 0207 456 0916.
Copies of the SPAB's range of Technical Pamphlets and Information Sheets are available to purchase from our online bookshop.
Apply to be an Angel!
The search is on to find winners for this year's English Heritage Angel Awards, the annual competition backed by Andrew Lloyd Webber to reward the efforts of local people in saving their heritage. So step into the limelight, apply yourself, on behalf of a group or nominate others! This year's Angel Awards will be bigger and better than ever with the search extended to include Grade II buildings and sites that have been at risk. The press release gives further details or you can go straight to the website for information about how to apply.
Sara Crofts ~ Education & Training Team Leader
