Humidity is where mould, odour and pests begin. What works without a dehumidifier, and when you actually need one.
Opening windows during rain lets humid outdoor air in. Open them briefly when the rain has stopped and outdoor humidity is below indoor — usually there is such a window during the day. A cheap hygrometer lets you decide by number rather than by feel.
Moisture builds first where air pools: wardrobes, under beds, under the sink. Simply moving air with a fan or circulator cuts mould dramatically at the same humidity. Keep furniture a few centimetres off the wall and leave wardrobe doors ajar now and then.
Dry mode on an air conditioner pulls moisture without cooling much, which suits the rainy season. If whole-home humidity stays above 65% for days, a dehumidifier is more efficient. Run it in a closed room, and empty the tank daily or it becomes the smell.
Drying laundry indoors raises humidity sharply. An extra spin cycle and a fan blowing directly on the rack nearly halve drying time. In the bathroom, squeegee the water after a shower and run the extractor 20–30 minutes longer — the surest mould prevention there is.
Managing humidity is much easier with numbers. A hygrometer need not be expensive, but place it near the middle of the room at eye level rather than on the floor or by a window so the reading represents the room. As a rough guide, indoor humidity staying above 60 percent for long periods encourages mold and dust mites, while below 40 percent skin and throat dry out. Readings differ within the same home, for example in the room next to the bathroom, a north-facing room or inside a wardrobe, so for the first few days move the hygrometer around to find the dampest spot and decide where the dehumidifier or absorbers should go.
For small closed spaces such as wardrobes and shoe cabinets, store-bought moisture absorbers are convenient. Calcium chloride types draw in moisture and collect it as liquid; once full they stop working, so check and replace them regularly. The collected liquid can irritate skin, so handle it carefully and keep the containers out of reach of children and pets. Newspaper works for drawing moisture out of shoes or boxes but must be replaced as soon as it gets damp. Charcoal and coffee grounds help with odours but do not noticeably lower the humidity of a whole room, so set your expectations accordingly.
A dehumidifier works only in a room with the doors and windows closed; left open, it keeps pulling in damp outside air and the reading barely moves. Keep it away from walls with space for air on all sides, and when drying laundry place it below or beside the clothes and add a fan for faster drying. Setting a target of around 50 to 60 percent stops it running more than necessary. A dusty filter lowers efficiency, and a tank left unemptied causes smells and bacteria, so wash and dry both regularly. Dehumidifiers give off heat, so expect the room to get a little warmer in summer.
Fighting damp has its own pitfalls. Leaving wet umbrellas and rain-soaked shoes in the entrance raises humidity right there, so shake them off and dry them before bringing them in. Keeping the wardrobe shut all the time because an absorber is inside actually traps stale air; open it on clear days to let air through. Clothes that already smell musty will not be fixed by dehumidifying alone, so wash them first. For some people, a long spell of damp conditions makes allergies or breathing problems worse. If coughing or a blocked nose persists, check your home environment and consult a medical professional.