Condensation

Bathrooms and kitchens, whether at ground or first floor level, are most susceptible to the effects of condensation. This is not surprising due to the volume of water used and consumed in these areas. A large proportion of this water is of a temperature which creates steam. The majority of bathrooms and kitchens in traditional properties had little or no ventilation incorporated in their original construction. This is wholly inadequate for the amount of moisture produced in these areas. This moisture then condenses on the cold walls and window panes. This causes the problems most often associated with condensation such as black mould (Aspergillus niger) and spore growth, de-bonding decorations and the saturation of ceiling and wall plaster. The provision of further natural ventilation often can be achieved by the installation of strategically sited high flow louvered air vents. If this is impractical or not an adequate solution then the introduction of some form of mechanical ventilation will be necessary. This could be in the form of a wall mounted humidity control extractor fan.

The UPVC and double glazing industry has grown dramatically in the last 20yrs. Advantages of UPVC double glazing / secondary glazing include low maintenance, and good thermal and acoustic insulation properties. This sealed unit concept has departed from the original softwood window and door design, which allowed a degree of natural ventilation through air leakage found in single glazed construction. Unfortunately, there is still a reluctance on the part of double glazing manufacturers to recognise the necessity of incorporating adequate ventilation in these window and door casements.

Many properties, flats in particular, have a warm air ducted heating system installed. This type of system, while originally thought to be acceptable, creates very high moisture levels through the imbalance and incorrect siting of ducts and heat outlets. This imbalance occurs through a disproportionate heat delivery system, causing various areas of the property to become overheated whilst other areas are under heated. Also, moisture is circulated through the ducting and subsequently throughout the dwelling area. The modern preference for central heating is for gas fired radiated systems. These systems are vastly superior to their warm air predecessors, and if operated correctly, create no inherent condensation problems. Unfortunately there is a universal tendency to use the wall-mounted radiators for the purpose of drying clothes. This misuse creates a heavily moisture laden atmosphere and drives relative humidity levels higher throughout the property.

A common oversight in the introduction of fitted bedroom and kitchen units is the omission of any form of in-situ through or cross ventilation. These units frequently encapsulate the entire surface area of the wall to which they are fitted. Wardrobe units especially contain moisture laden clothing and footwear which create a stale, humid atmosphere which, when transferred to cold spots condenses, creating conditions conducive to the growth of mould and spores. These problems are mostly associated with modern living methods and can be overcome by the introduction of ventilation, both to the front panels of the units, and also to the exterior wall where possible.

Properties built between the late 50’s and mid 80’s of 11” cavity wall construction have been the target of aggressive advertising with regards to the merits of the installation of cavity wall insulation. The method of polystyrene in-fill often creates additional problems through uneven distribution of the in-fill material, and the creation of cold spots across the area of the wall. This problem is also increased if there is any obstructions within the cavity itself e.g. builders rubble or mortar droppings. This defeats the original design principle of the cavity wall, where moisture could evaporate naturally inside the 50mm void between the brickwork skins. This causes both the internal and external skins of brickwork to ‘sweat’ and increases moisture content, which is noticeable through staining visible on internal decorations. Although the installation of cavity wall insulation may seem financially attractive with regards to the savings achieved on heating bills, the adverse effect is to create a vacuous, over insulated property by not allowing the organic construction materials to function in the way they were originally designed. A full appraisal of the design of each individual property should be carried out before consideration is given to the installation of cavity wall insulation

Due to the introduction of the ‘smokeless zone’ and the prohibiting of the burning of fossil fuels, this has introduced the universal installation of central heating in to dwelling houses. If the original chimneys are capped, sealed and non-vented, this will cause ‘sweating’ and staining to occur, leading to the migration of salts and nitrates to the surface of the wall finish.

Condensation can occur at roof level as well as at all other levels of dwelling houses, offices and flats. Roofing details are often designed to include provision for ventilation at eaves or soffit level. Because of there being so many exposed timbers in the roof construction of most properties, condensation in the roof space can cause many problems. When the Relative humidity of a roof space increases to the dew point, the timbers in that roof space begin to ‘sweat’. Over a period of time this will undoubtedly lead to problems with fungal decay and/or timber pest infestation. Plaster work to the ceilings below may also become affected by the high moisture content of the roof timbers. One of the most common causes of condensation in the roof space is over-insulation and the subsequent restriction of in-situ ventilation channels (e.g. soffit and eaves vents). Ventilation methods and channels should under no circumstances be blocked up to restrict the flow of air. If condensation is still present with the existence of in-situ ventilation, then additional roof slate and ridge tile vents can be installed on the slopes and ridges. In addition, high flow louvered air vents can be installed to any brick gables which may be present.

When properties are unoccupied, generally little or no heating is required. This causes internal and external surfaces to remain cold. As a consequence of re-occupancy, normally in the early evening, moisture levels throughout the property are increased and air quality reduced through everyday activities such as cooking, bathing and respiration. This problem can be answered through a balance of both heat and ventilation working in conjunction. When this balance is achieved this will create a cleaner and more healthy living environment.