We have a mould problem in our houses in Aotearoa.

Once you see mould, you need to deal with it quickly to make sure it doesn’t continue to grow and spread. Some species, like the infamous black mould – Stachybotrys chartarum – are toxic.

Other more common species can trigger allergic reactions or set off asthma symptoms. This is because mould produces thousands of tiny spores that float in the air. It’s imperative to remove the growth of mould for the immediate health of your home, not to mention to stop the structural damage over time to your building materials.

Generally speaking, it’s relatively easy to stop mould from growing in the first place, but that’s only one part of the solution. You also need to deal with any emerging mould that’s growing on surfaces in your home.

Stop mould from growing in the first place

Whether you own a house or rent, you should make these changes to prevent mould from forming:

Remove water sources

  • Dry washing outside rather than inside on a clothes horse.
  • Don’t use portable gas heaters indoors, they pump moisture into the air. (1 litre of moisture for every hour it is running)
  • Deal with water leaks, clean up spills, and mop up condensation as it forms. Wipe any moisture or drips off your windows and walls.
  • Install a vapour barrier under the house to stop moisture coming up from underneath.
  • When cooking, use your rangehood or open the windows.

Ventilate your rooms

  • Use an extractor fan when cooking or showering (and leave on for approx. 10 mins after using).
  • Open all the windows for 10 minutes a day to help remove the damp air that’s built up inside and then close up again.
  • If you have a mechanical home ventilation system (like an HRV or DVS), make sure it’s on and well maintained.
  • Keep beds and furniture away from walls, leaving a gap so air can circulate freely.
  • Keep wardrobe doors slightly open.
  • Avoid putting mattresses directly on the floor.

Heat the place

  • Warmer air holds more moisture so it’s harder for condensation to form.
  • Open curtains during the day to let warmth in and close them just before dark to keep the warmth in.

Dealing with the mould you can see

The most likely places you’ll find mould in the home is around window frames and bathroom ceilings, and the backs of curtains. Don’t forget to check behind furniture (think chest of drawers) and in cupboards too as it’s hard to ventilate these spaces.

Small patches can be dealt with using soapy water and then drying the area well.

Large patches or growth found behind walls should be tested to see if it’s Stachybotrys chartarum. If you suspect it might be black mould, it’s best to call in the experts to deal with it and keep yourself safe.

Why does mould grow in our homes anyway?

Mould needs moisture to grow, and our damp houses are the perfect breeding ground. It mainly comes down to our climate – NZ is a muggy place with high humidity, so there’s a lot of moisture in the air. In winter, when the air cools, it condenses and loses its ability to hold as much water, leading to condensation forming on surfaces like your cold windows.

When we have a sustained period of cold, rainy weather, humidity in your home can stay high for sustained periods. That’s all the invitation mould needs to form and grow.

Thanks to Consumer for this article.