How to prevent mould at home in winter

In winter, mould appears because the home has a lot of water vapour and too little fresh air. To prevent it, ventilate every day, keep the home at a steady temperature and avoid drying laundry indoors without ventilation.

Ventilate every day

It may seem odd to open the windows when it is cold. But the air inside holds more moisture than the air outside. When you change the air, you remove water vapour from the home.

Open the windows in the morning for ten to fifteen minutes.
If you can, open windows on opposite sides of the home to create a through-draught. The air changes more quickly that way.
Do this even on rainy or foggy days. Cold air from outside usually holds less vapour once it warms up inside the home.
Do not leave windows just slightly open for hours, because that cools the walls without properly renewing the air.
Open wardrobe and cupboard doors from time to time, especially on external walls.

Kitchen and bathroom

This is where most vapour is produced. A hot shower fills the bathroom with moisture within minutes.

Switch on the extractor fan or open the window during the shower and for a few minutes afterwards.
Close the bathroom door so the vapour does not spread to the rest of the home.
When cooking, put lids on pans and use the extractor hood.
Wipe the tiles and the shower screen or shower tray glass with a squeegee or cloth after showering.

Drying laundry

A full load of washing hung indoors releases a lot of water into the air. If possible, hang it outside or on a sheltered balcony.

When you have to dry it indoors:

Choose a small room and close the door.
Open a window or use a dehumidifier in the same space.
Spin the laundry well before hanging it.
Do not hang laundry on radiators without ventilation.

A tumble dryer that vents to the outside also helps. Condenser models need the water tank to be emptied.

Heating

Cold walls encourage condensation. It is better to keep a moderate, steady temperature than to heat only now and then. Big swings in temperature make vapour condense on the walls.

Heat bedrooms a little, even if you do not use them during the day.
Avoid gas or paraffin heaters with no flue. They release a lot of water vapour.
Do not cover radiators with clothes or furniture.

Furniture and storage

If a piece of furniture is pushed against a cold wall, air cannot circulate and mould appears behind it.

Leave a few centimetres between the furniture and the wall.
Avoid overfilling wardrobes on external walls.
Do not leave mattresses leaning against cold walls. Lift them from time to time to air them.
Dust the walls and corners, because mould also feeds on dust.

Signs to watch for

If you see water droplets on the windows, a musty smell or small dark patches in the corners, act straight away. Clean the patch carefully, wearing gloves and a mask, and step up the ventilation. The sooner you act, the easier it is.

Tip: A simple, inexpensive hygrometer shows the humidity of the air in the room. If it is very high most of the time, the home needs more ventilation.

In homes near the sea, in Cascais or Oeiras, and in the cooler parts of Sintra, the air is naturally more humid. Ventilating regularly and drying the home well helps even more. If the mould keeps coming back anyway, there may be a leak or a problem with the wall. Ask a professional to assess it.