Reducing condensation

Surveys range from the single visit of a pre-purchased survey (a 'snapshot survey' undertaken before a property is bought, rather than at a chosen time of the year) to surveys in the contact of a managed housing stock, when the property may well have been closely inspected a number of times previously, and will have a known history in terms of the building's past condition, repairs, improvements and, most importantly, occupancy.

Dampness investigations of managed housing stock are extremely thorough and time consuming, often involving more than 1 visit. They include approaches beyond the scope of the pre-purchase surveys, e.g. where monitoring of moisture conditions may take place using date loggers for remote monitoring. Such a survey could be taking place in the context of a legal dispute, where detailed evidence of condition is required.

Cases of serious condensation mould are a particular problem in the rented housing sector due to 3 key factors:

• 'fuel poverty' of occupiers, i.e. they cannot afford to heat the property adequately;
• the buildings may have shortcomings in design making them difficult to keep comfortably dry; and
• tenants being unaware of how their lifestyle habits could be making the damp problem worse.

Whenever you inspect property with condensation or likely condensation problems, you must be fully aware of the significance of the time frame in which you are surveying the subject property, and note this in your report. If the property is occupied, assess the most appropriate timing of your visit, i.e. at the time of day condensation is likely to be occurring, and during the 'condensation season', September to March.

Most pre-purchase surveys of houses are single visits only. The survey takes place at a particular time of the year, on 1 day of the week and during 1 part of the day. The property may or may not be occupied at the time of the survey, and condensation could be occurring outside the time slot of the survey. You may have no knowledge of the history of occupation of the dwelling, and may have no contact whatsoever with the current resident. This means that you cannot bring together the full evidence of building lifestyle, condition and design on which diagnosis of condensation-related problems needs to be based. Such limitations on diagnosis must be stated in your report.

Data loggers may be used by specialist investigators to monitor internal conditions, but can also be seen to be monitoring lifestyles. Cultural differences in activities like cooking, cleaning, washing and heating may have a significant impact on moisture generation within the home, and may need addressing with patience and tact.

BRE Report 174 Tackling Condensation recognises the difficulties surveyors face and includes useful advice on symptoms, causes and remedies for condensation problems. The report offers practical advice on matters such as the timing of site investigations.

Visual inspection will confirm whether mould development has resulted on internal surfaces, and there will be occasions when you will see condensation actively taking place - particularly if the property is occupied. There may also be historic mould present that developed some time ago and that does not reflect a current condensation problem.

You may use moisture meter accessories to establish whether or not the conditions of air temperature, relative humidity and surface temperature are present to cause condensation at the time of your survey. Modern moisture meters calculate the dew point and use surface thermometers to then confirm whether condensation is taking place on a surface, or how far the temperature is from dew point.

Research into a property’s recent history concerning occupation, number and ages of occupants, occupancy pattern, heating pattern and family economics can be important. Many families suffer from fuel poverty, so some rooms are left unheated or unsatisfactory heating appliances are used, i.e. those that actually generate moisture in the air - gas bottle and paraffin heaters being examples. Evidence of use of unsuitable portable heaters may be there to see. There could also be evidence of unsuitable washing and clothes drying methods.

Key surveying procedures

Key dampness investigation strategies are explained fully within the stages 1-4 investigation strategies (see Damp investigations).

You will often find symptoms of mould development. You may often also use the electronic moisture meter (EMM) to find out whether wall finishes appear to be 'damp'. Plot the pattern of readings to help your diagnosis. Readings obtained need to be carefully assessed as described under the Stage 2 investigation techniques. Put high readings (i.e. above 16 R/R - or 16% for timber) in perspective in view of the possible false readings that can sometimes be obtained using an instrument essentially calibrated for timber and easily influenced by metals, salts and carbonaceous material. If wall plasters are significantly damp, you need to know whether the wall is significantly damp within its thickness, if a firm diagnosis is needed. If the wall is significantly damp at depth there could be other moisture sources to investigate.

Ascertaining moisture conditions deep within a wall, using for example deep insulated probes or testing a drilled sample with a carbide meter for moisture content, it may be possible to confirm that air moisture condensation is in fact the lead moisture source, and an appropriate remedy may be decided upon.

Following the chain of events

Confirming condensation is not a diagnosis: it is the starting point for further investigation to establish cause. This is because condensation is not technically a source. For example, moisture found at B, a spare bedroom, may have been generated at A, the kitchen. When condensation is found to be a problem, you must look further to find out how and why it has occurred, and the impact of the various contributory factors such as climatic effects, building condition and the way the building is lived in.

You may need to follow the moisture trail back from the observed condensation-led mould to a massive moisture generation occurring in another room of the house - e.g. where clothes are seen drying on radiators.

Just stating that there is evidence of a condensation problem would not offer a client sufficient information. You must consider how and why the condensation is occurring, alternative strategies to reduce or eliminate the problem, and as discussed earlier, a prognosis - the implications of not remedying the problem for the building and its users.

Condensation must be viewed as the end result of an often complex network of contributory factors, and your diagnosis must include investigation into those contributory factors to enable recommendations for an appropriate remedy to be formulated.