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CONDENSATION
Condensation occurs in a property from the behaviour of the air and moisture relationships. The risk of condensation depends on the moisture content of the air and the temperature that it will encounter. Condensation occurs when air encounters temperatures below its dew point, and dew point depends only on the moisture content of the air.
Relative humidity is the amount of water vapour in the air at any given temperature expressed as a percentage of the maximum amount of water that can be held at the same temperature. Therefore, Relative humidity is a proportion not an amount. Dew point is the temperature at which condensation occurs.
The Relative humidity of air with a particular moisture content will vary with temperature. So as the air is cooled the Relative humidity will increase with the surplus moisture released as condensation, (Dew Point).
Mould growth such as Aspergillus niger, Penicillium, Cladosporium, are associated with surface condensation. Mould spores readily exist within the atmosphere, and to germinate they need oxygen, nutrient, moisture, and a suitable temperature. Moulds and mildews can also be found on furniture, curtains, clothes, leather goods, etc. that are in unheated spaces with minimal ventilation. Such as unused bedrooms, cupboards, wardrobes, furniture placed tight against external walls.
As moulds are hydrophilic fungi they require high levels of moisture, such as free water created by condensation.
Ground water from rising or lateral damp penetration will be contaminated with hygroscopic salts, Commonly Chlorides and Nitrate salts, which will displace the water molecule in the moisture causing dehydration of the mould preventing its growth. This can sometimes assist in the diagnosing the cause of dampness when there is a high moisture presence but lack of mould discolouration.
The internal surface of cold inadequate or uninsulated walls are therefore susceptible to the attraction of warm moisture laden air within the property to condense on. The Relative humidity at the cold external wall surface will be high enough to support the growth of mould.
EMC Surface Finishes can improve the Thermal properties of the external wall fabric by installation of a suitable retrofit insulated plaster system.
External insulated Render systems significantly reduce the energy loss by encapsulating the building in a thermally resistant envelope, maintaining a comfortable internal temperature with no internal disruption during installation. There are a range of anti-crack, through coloured, waterproof finishes.
Internal insulated plaster systems such as insulated plasterboard mechanically affixed to the internal surfaces of the external walls and skim finished. However, this can reduce the internal space due to the required thickness, with additional works involved in altering joinery finishes, radiator pipes, electrical sockets, etc. to accommodate the increase in thickness to the wall surface.
As an alternative we recommend the installation of Iso-Therm thin wall insulation, as it is vapour permeable, but waterproof therefore resisting any lateral damp transference and highly resistant to any formation of surface mould. Reduces heat loss, improving the U value of the wall, therefore greater reduction in energy consumption. Being +/- 4mm thick minimally invasive in its installation.
In conclusion condensation control can mainly be addressed by the occupier of the property by adjusting their living habits. Three fundamental ongoing activities are to initially improve the thermal and vapour properties of the construction fabric of the building and maintain a moderate but constant background heat coupled with good ventilation.
PROPERTY CARE
Where damp problems do exist, it is recommended that EMC Surface Finishes initially carry out a survey first to ascertain and diagnose the cause of the dampness and design an appropriate repair specification.
Or at least we recommend that a specialist surveyor who is registered with the Property Care Association (PCA) is employed to provide a survey. The Property Care Association is a trade association representing property preservation specialists and have a wealth of helpful information on their website. www.property-care.org
vapour permeable, but waterproof
EMC Surface Finishes are committed to assist and deliver you with all your plastering requirements, from original to modern realisations, with a sympathetic approach to help you achieve your design requirements.