Condensation

Moisture is present in the air around us, to a greater or lesser degree; this is called air humidity. The warmer the air, the more moisture the air can hold. When this warm air meets a cold surface, or a front of colder air; the temperature of the warm air drops and the moisture is released to form water droplets. Windows and car windshields provide a very good example of this mechanism. Heat generated from central heating, baths and showers, cooking, and even just breathing in an unventilated room, can all cause condensation. Condensation can be extremely difficult to eradicate completely, but it can be greatly reduced. The two main methods of reducing condensation in the home are; reduce the amount of moisture in the air, or remove the condensation by means of extraction.

In addition to roof leaks, condensation in the roof space can lead to major problems if ignored. This can result in the (timber) structural members of the roof becoming damp, which can, with time cause rot and infestation. The roof space, given the right conditions is one of the most favourable areas in the home for condensation to exist and flourish.

 

It is important that adequate ventilation is provided in the roof space. In days gone by, it was common practice to butt loft insulation materials tightly into the corners of the loft space, where the underside of the roof meets the ceiling. This is now recognised as bad practice; loft insulating materials should not extend to the end of the ceiling joists and block the gaps that would otherwise allow air to enter the roof space and circulate.

Loft insulation will halt, or certainly reduce the amount of heat that escapes through the roof, but it will not necessarily stop or eliminate the moisture that is carried up with the heated warm air; rather, the moisture will settle on the roof insulating material, spread to the joist timbers, and lay dormant, and decay. Without adequate ventilation, and therefore a means of escape, this moisture can lead to dampness and possibly, more serious problems.

 

In some homes, the plaster board ceiling sheets are constructed with a foil covering on the side of the sheet that faces the roof space. This enable the moisture to pass through and escape, but blocks the passage of the heat

Condensation is generated from everyday activities within the home such as cooking, bathing, and washing. Extraction is the most effective method of eliminating excessive condensation.

Extractor fans over cookers, even when vented outside, give only limited means of condensation escape. They are effective for only the condensation generated within a very small area. Simple fabric filters do nothing for ventilation purposes. They are designed to merely extract the “grease and other solids” generated during the cooking process, and just re-circulate the moisture laden air.

 

Also, simple air, or draught powered ventilators and air bricks are only as effective as the direction of the prevailing wind! Under prevailing conditions, they can actually bring moisture swollen air into the home.

 

Powered extractor fans are a very effective means of extracting condensation, particularly when they are installed in a number of rooms in the home, especially those rooms where steam is frequently generated i.e. kitchens, bathrooms and shower rooms. For this reason it is common to install a number of powered extractors within the home.

Condensation is produced by a variety of common house hold appliances. A tumble dryer, for example, should always be vented outside if it is not the condenser type of machine. Where possible, install an efficient extraction system in the bathroom and kitchen. Boilers, fridges and even washing machines will generate heat, not perhaps to a degree that it is required to be vented outside necessarily; but heat that never less raises the room temperature.

Extreme condensation problems may be solved with the installation of an air exchanger. An air exchanger is a piece of equipment that extracts the moist air from a home, or building, and feeds in fresh warm air, without a resulting drop in room temperature.