Condensation is one of those seasonal events which takes place every year with out fail around the time the clocks go back. Windows start to steam up, mould growth starts to grow and you know condensation has returned.
Condensation will occur in the colder months somewhere in nearly every property, either housing, commercial or industrial, unless appropriate remedial precautions have been taken. It is the largest single complaint received by landlords in both the public and private sectors, and generally a self-inflicted problem by the owner-occupier.
Condensation is caused when warm, moist air meets a cold surface and the water vapour "condenses" .
The capacity of air to hold water is related to temperature; warm air holding more water than cold air. Air is saturated when it cannot hold any more water vapour at the existing temperature and therefore has a relative humidity (RH) of 100%. If the temperature of the air falls until saturation point occurs, the air is at a critical temperature or dew point where any further fall in temperature will result in water vapour being forced to condense out as liquid water.
The condensed water usually shows as droplets on windows and other non- absorbent surfaces. This is surface condensation; it is fairly obvious and always occurs on the surfaces which are at or below the dew point of the air immediately adjacent.
The water vapour inside a building also contributes to a greater overall air pressure. This results in the outward movement of warm, moist air through the structure of the building. This could eventually cool below its dew point within the fabric of building resulting in interstitial condensation.
Interstitial condensation is more complex than the surface form and presents a greater hazard. It can go undetected for long periods until serious damage has developed such as timber decay.
There are four main and interrelated factors which affect the occurrence of condensation in a building:-
- Moisture generated within the building
- The ventilation system provided and use made of it
- The heating provided and use made of it
- The thermal capacity and insulation.
The first two factors are normally the primary causes because moisture generated by domestic activities can be significant and the fact that most buildings are effectively sealed to prevent heat loss means there is no background ventilation to allow the moist air to naturally filter out of the building. Features such as double glazing and draught excluders cause problems associated with poor air circulation, as this can lead to stale air as well as condensation.
Condensation is quite often found in kitchens and bathrooms, but warm moist air can also spread to cooler parts of the building such as bedrooms to condense on any cold surface. Here the first signs to the occupier will be mould growth.
The appearance of mould creates concern about damage to furnishings, decorations, unpleasant smells and possible affects on health.
Advice to Landlords
Under the Housing Health and Safety Rating system, mould is listed as a class one health hazard, as such, it is treated very seriously by environmental health officers. Landlords are responsible for ensuring that their properties are free from risks to the tenants’ health and have a duty to provide adequate heating and ventilation; what is more, under EU regulations concerning fuel poverty, opening windows during the space heating season to ventilate is no longer a viable defence.
High relative humidity levels are quite common place in properties these days as our drive for energy efficiency has seen houses built more tightly and effectively “sealed” up with insulation and double glazing. As we cook, bathe and breathe, up to 4 pints of moisture per person per day is trapped in the property.
Positive Input Ventilation units (PIV)
A habitable room should be ventilated so that all the air is replaced at least once every hour. Air replacement in high risk rooms such as bathrooms and kitchens should be much greater than habitable rooms. Building Regulations now recommend that this is achieved by having permanent ventilation of at least 8000mm2 ( equivalent to a 4 x4" hole in an outside wall) and rapid mechanical extraction in high risk rooms.
How PIV works
The solution is Positive Input Ventilation (PIV). The Positive Ventilation Units are sophisticated whole home ventilation and condensation control units. By drawing in fresh, filtered and clean air, the units gently ventilate the home from a central position on a landing in a house or the central hallway in a flat or bungalow.
Moisture laden air is diluted, displaced and replaced to control humidity levels around 55%. This significantly reduces or eliminates surface condensation, the main cause for mould growth and hence mould problems. With lower humidity levels, dust mite populations are also substantially reduced to provide a significant improvement in the health of asthma sufferers and general indoor air quality.
Durham Preservation will carry out a professional assessment of the property and recommend a bespoke ventilation system to cure individual property needs.
Condensation Treatment and Inspection Surveys available for our offices in Durham Newcastle York Carlisle and Cumbria.