Penetrating damp, rising damp symptoms, condensation
The stain evident on some section of the wall, is normally a sign that water drawing pigmentation as it passes through brick or timber.
Exposed brick allows absorption and evaporation of water. Partial render causes water to become trapped, forcing onto the inside wall.
There is no externally ducted kitchen extractor fan and the windows don’t have trickle vents. It is likely that the walls are becoming cold at night, at least below the dew point.
Sub-floor was humid which typically results in condensation forming on the damp proof course, causing rising damp like symptoms. Clear the drain and ideally have it checked for cracks with a CCTV drain survey.
Relative humidity is a measure of how much vapour is in the air compared to air’s capacity to hold vapour. It is a function of vapour pressure (quality of vapour) and temperature. As temperature rises, air can hold more vapour. Conversely as temperature drops, air holds less vapour until it reaches the point of saturation when condensation starts.
Dew point is the temperature where condensation takes place. It is also a proxy the vapour pressure. Comparing the dew point of one area to another makes it possible to see where vapour is being generated or conversely removed (normally through ventilation).
In conclusion from the dataloggers
- During the 2 weeks under observation the relative humidity is often near or above 80%RH in the kitchen and hallway, high enough for condensation and mould to form.
- The temperature is being held very constant, which is excellent, and will reduce the risk, however it is not yet winter. For each -1°C the relative humidity will be about 5%RH higher. The effect increases as the temperature difference between inside and outside increases such as on a cold winter’s night.
- The dew point is consistently at or below external dew point, suggesting adequate ventilation in its current unoccupied state. However, I don’t believe ventilation is sufficient when occupied.
- I believe that following my recommendations and monitoring improvements, should drive down relative humidity and reduce the risk of condensation and mould forming.
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