Kitchens: Steam from cooking and washing up is the main source of moisture in the kitchen. The most effective method of removing the steam is to install an extractor fan and a range hood ducted to the outside air. Replacement air should be allowed to enter the kitchen, preferably at a low level from the opposite side of the room, either through a window, a door or a ventilator.

Natural ventilation is not as good as that provided by the fan and hood. Opening the windows and allowing the wind to blow in may only clear the kitchen steam by moving it to other rooms. For this reason kitchen doors should be self closing.

Any build-up of mould on the walls or ceiling should be treated with a bleach/water solution or commercial mould remover. Mould may form on the mortar between tiles, especially in shower recesses. To remove, wipe over with a bleach/water mixture or use a mould remover. Check at regular intervals to make sure there is no recurrence of mould growth.

Circulation Areas: Halls, stairs and passages should be well ventilated. If the doors are kept closed the moist air may condense in these areas on the ceilings or walls.

Picture Windows and Glass Doors: Condensation can readily occur on large areas of glass. The walls below can become almost permanently damp and pools of water may even form on the floor. Opening the windows slightly to allow ventilation will cure most problems. In particularly bad cases the best remedy is to have a condensation channel installed with weep holes to the outside of windows.

Ceilings: Condensation can form directly on the underside of a ceiling. It is caused by the entry of cold air via metal roofing or through tiling. In the absence of ceiling insulation, moisture can lie on the ceiling of an unheated room. A ceiling can become so cold that water vapour may form from air in the room beneath. Thermal insulation laid over ceilings will reduce problem beneath pitched roofs. It will also reduce the tendency for organic growth to form on ceilings decorated with paints that are not inherently fungus resistant.

Pantries (Larders): These rooms should be ventilated at both high and low levels. A 15mm gap should be left between shelves and the wall to allow free circulation of air.

Bedrooms: Bedrooms in many homes are the coldest rooms in the house. Water vapour from other, warmer rooms may be carried into bedrooms and condense on the walls or, more often, on the windows.

The solution is to keep bedroom doors closed and remove water vapour through exhaust fans in the kitchen and bathrooms.

Wardrobes and cupboards built on external walls may be a condensation hazard. The contents - clothes, shoes and other items - may be damaged by mildew and mould growth. The best solution is to ventilate these storage areas by using louvered doors or drilling holes in the door(s) at both high and low levels. Clothes should be taken out and aired at regular intervals, especially if a period of humid weather is experienced.

Bathrooms: Bathrooms are frequently subjected to temporary condensation during and after showers and baths. This is usually only a minor problem, but the moist air can cause mould formation if ventilation is poor. Windows should be opened for ventilation during and after showering or bathing. Gloss paint on the walls and ceilings will assist the evaporation of moisture.

If condensation is a major problem, an extraction fan should be installed in the external wall. It should be turned on during or after a shower or bath to blow the moist air out of the room.