As soon as the temperature drops overnight, damp in the house makes itself known: steamed-up windows when you get up, a musty smell in the hallway, a dark patch behind the wardrobe. It is nothing unusual and it is almost never irreversible. In most homes the problem is condensation, and it is fixed with a handful of concrete habits. Here they are, in order of importance.
Why damp comes back to the house every autumn
Warm air holds far more water vapour than cold air. While the weather is mild, that vapour circulates without us noticing. In autumn it meets surfaces that are already cold — the glass, the corner of an external wall, the windowsill — and turns back into liquid water. That is condensation.
The amounts involved are surprising: showers, cooking, drying laundry indoors, your own breathing. A family of four releases several litres of water a day inside the house. If nothing carries it away, it settles on the coldest surface it can find.
Three signs worth watching
- Condensation on the windows when you get up, especially in the bedrooms. It is the first warning and the easiest one to overlook.
- A musty smell that comes back a few hours after you have ventilated.
- Black patches in the corners, behind furniture pushed against external walls or on the bathroom ceiling.
A hygrometer costing a few euros settles any doubt: the ideal relative humidity sits between 40% and 60%. Above 65%, mould finds room to take hold.
Ventilate for ten minutes, twice a day
This is the most effective habit and, at the same time, the worst executed. Throwing the windows wide open for ten minutes in the morning and another ten in the afternoon renews all the air without cooling the walls: the house is back up to temperature within minutes. If you can, open up at two opposite points to create a through draught and you will be done even faster.
The opposite — a window left ajar all morning — chills the masonry, sends the bill up and barely renews the air. And turn the radiators down while you ventilate. If you have mechanical ventilation, never cover the vents, clean them a couple of times a year and keep the window air inlets clear.
Room by room
Bathroom. Shower with the door shut so the steam does not spread through the rest of the house, then ventilate or run the extractor fan for twenty minutes afterwards. Running a rubber squeegee over the shower screen and the tiles removes a good glassful of water in ten seconds.
Kitchen. Lids on the pans and the extractor hood on from the moment you start cooking, not once everything is already full of steam.
Bedroom. Pull the headboard a few centimetres away from the external wall and leave the duvet folded back instead of pulled flat when you get up: the mattress needs to release the moisture from the night.
Laundry. Drying clothes indoors is the most underestimated source of damp. If there is no way around it, do it in a closed room with the window ajar, never spread around the living room.
Heat steadily, not in bursts
Between 19 and 20 °C in the living areas and around 17 °C in the bedrooms is enough. Alternating a freezing house during the day and an overheated one at night is the perfect recipe for condensation: the walls stay cold and concentrate all the moisture that an evening at home produces. A steady temperature, even a moderate one, dries better than peaks of heat.
When it is no longer condensation
If the patch always reappears in the same spot despite ventilating, if there is a tidemark along the bottom of a wall or if you see whitish salt deposits on the plaster, we are no longer talking about vapour: that points to rising damp, to water getting in or to a leak. Ventilating is not enough there and it needs a diagnosis; the sooner you get one, the cheaper the repair.
A dry house is a house you enjoy
Once the damp is under control, autumn at home is a different thing altogether: no strange smell, the laundry smells clean and you actually want to stay in. From there it is a matter of finishing the room off with textiles and warm details; in our selection for the home you will find ideas for that pleasant part, the one that comes after the ventilating.