How do you know it’s winter? When the windows start dripping. While it might seem like just another staple of New Zealand homes, you don’t have to put up with a pool of water at the bottom of your windows every morning.

How condensation forms and why it matters

Condensation is the result of water warming up, evaporating, then turning back into a liquid once it touches a cold surface. You know when you breathe onto a mirror and you can use your finger to write messages in the remaining mist? That’s condensation. The same thing happens with the moist air in your home and your cold windows.

What’s the big deal about moisture anyway?

Moisture doesn’t just make your home feel cold and damp, it causes mould too. Mould has all sorts of nasty effects on your health and it thrives in wet environments.

The condensation on the inside of your windows is a good indicator that there is too much moisture in your home. You can get accurate readings from a ‘hygrometer’; a cheap little device that you can get from many hardware stores that tells you exactly how humid the room is.

Ideally, you’d use one in each room of your house over the course of a few days to get an idea of which room is in most need of attention. If the reading is over 65% relative humidity and below 18 degrees Celsius, it might be time to take the following steps, depending on the room.


Boiling water and cooking kai releases up to 3 litres of water every day—it’s one of the worst offenders in the fight against wet windows. Doing the dishes isn’t much better, contributing up to 1 litre per day. To reduce the impact, remember to:

  • Keep the extractor fan on. Your range hood should be larger than the cooking surface it’s venting, and should be venting directly outside—not to the roof space. Otherwise, it might end up damaging the insulation and internal roof structures. If you’re renting and the extractor fan doesn’t tick those boxes, it’s worth discussing with your landlord. They don’t want moisture or mould in your home either.
  • Keep pots covered. If you’re boiling potatoes, pasta or just making a cup of coffee or tea, keep the lid on while the water heats up and while the contents cooks. Not only does this keep the steam inside, it also means the water boils faster—less energy used, a lower utility bill, and a faster dinner!


Don’t worry, cleaning your teeth isn’t spreading moisture into the air, no matter how vigorously you scrub. But the bath and the shower certainly are, with each person releasing 1.5 litres of water per day with their washes.

  • Keep the extractor fan on. Just like in the kitchen, extractor fans should be venting outside, not into the roof. In the case of the shower, you should also try to keep the fan running for at least 5 minutes after a shower or bath is finished, preferably with the door open.
  • Use a shower dome. A shower dome is a glass dome over the top of the shower that catches the upward drifting steam and condenses it back into the shower before it has a chance to escape elsewhere. If you don’t have one and you’re renting, speak to your landlord about having one installed – they have been shown the help reduce humidity.


Here’s a real moisture maker! Doing the laundry releases 5 litres of water for every load if the dryer isn’t vented. But don’t worry, it’s easy to avoid:

  • Avoid drying indoors. Sunny winter days might be rare, but they do exist. Take advantage of them by drying laundry outside. If you can at least start the dry outside and finish it inside in the dryer, not only are you keeping the moisture out, but you’re cutting your costs too. You can read more about that side of things in our dedicated cost-cutting guide.
  • Spin rather than dry. You can use the washing machine to spin out the water rather than rely on the dryer to use heat to do it. This sends the water down the drain rather than into the air, so don’t be afraid of throwing the clothes into another spin cycle at the end of a usual wash. Just be careful of delicate fabrics.

Living areas

Unlike other places in the home, living areas don’t tend to have any direct water sources for moisture to come from. However, they still have a part to play in the fight against mould.

  • Reconsider your interior design. Bear with us here. The design of your living room could be contributing to the amount of water on your windows. If you leave a gap of at least 10cm between furniture and outside walls, it improves the ventilation of the whole room. That makes it warmer and means that heavy moisture-laden air doesn’t get trapped behind the sofa.
  • Keep the place warm. Warm air holds more moisture than cold air. In winter when it’s cold, more water can get into the air and eventually onto your windows. You can beat that by keeping the inside of the home as warm as possible. Keep the fire stoked, insulate as much as possible, and don’t use unflued gas heaters. They release a litre of moisture into your home for every hour they’re used. You can read more with our guide to the cheapest ways to heat a New Zealand home and our dedicated guide to cheap ways to keep the cold out and the warm in.
  • Dehumidify or… Dehumidifiers are relatively cheap tools to eliminate moisture that you just can’t get rid of with any other techniques. If you buy a ‘dessicant’ version, it also heats the room, making it a double whammy for mould. If you’re spending a lot of time in the living room, consider investing in one and making sure you keep doors and windows closed as you use it. They generally only work for the room that they’re in, so move it around the house if you have more than one trouble spot.
  • …Air out the house. It seems backwards, but cracking open the windows for 10 to 15 minutes a day can be enough to chase moisture out of your home. Of course, it also lets out all of the heat, so it’s a trade-off. It’s best to air out the house at around midday, when outside temperatures are highest.


Did you know that we generate moisture in the air simply from breathing? After 8 hours of sleep, that’s a lot of moisture.

  • Place furniture carefully. Just like the living room, keeping your furniture about a hands width away from the walls (including the bed) will improve ventilation and stop moisture from getting trapped. Put mattresses on a bed base if you can, or put them on their side during the day if you can’t. Also try cracking open the wardrobes and drawers. This will help air out your clothes and stop them from absorbing any moisture already in the air.
  • Use a dehumidifier (at night). Using a dehumidifier in the bedroom at night time can reduce dampness. Make sure to wipe away that condensation with a sponge in the morning if it does show up. Then squeeze it out into the drain or outside.

If condensation persists…

If you do all of this and you still get condensation on your windows, there might be bigger issues at play. You may need to get a weathertightness report from a building assessor—something that renters can discuss with their landlords.

But a lot of the time, these tips and tricks are enough to wave goodbye to weeping windows, leaving behind a warmer, more comfortable, less mouldy home. If you are left with mould on your curtains, we can remove it and leave them sanitised and good as new. Call us on 0800 5790501 to book in.

Thanks to Avanti Community Hub for this article.