Winter condensation vs summer humidity

Summer humidity

On sticky summer days, indoor relative humidity can sit above 70% for days on end, especially in poorly ventilated rooms and inside air conditioning units and ducts. Even when you can't see it, that moisture can work its way into walls, carpets and ceiling cavities, leading to musty smells and damage to materials over time.

When humidity stays high, dehumidification makes a real difference. A portable or built-in dehumidifier helps keep your home below 60%, and ideally between 30% and 50%.

Winter condensation

In winter the problem flips. When warm indoor air meets a cold surface, such as an uninsulated wall, a window or a ceiling under a cold roof, it cools and releases moisture as droplets. That's condensation, and it is often the first clue mould could follow.

You'll often see it behind furniture pushed against external walls, around window frames on cold mornings and in rooms that aren't heated. Cold can also travel through solid materials such as concrete and brick, creating cold spots on inside surfaces. This is known as thermal bridging.

• Leave a gap between furniture and external walls.
• Keep air moving with fans or vents.
• Improve insulation where you can.
• In cooler weather, desiccant dehumidifiers work better than refrigerant types below about 20°C.

Year round

Whatever the season, the moisture comes first. Cleaning won't stop mould returning while the leak, dampness or humidity remains.

• Use exhaust fans that vent outdoors, not into the roof space.
• After a shower, squeegee tiles and glass and leave the fan running until surfaces are dry.
• Check for condensation and leaks after cold snaps and heavy rain.

Managing moisture takes a little effort, but it is far easier than dealing with mould once it's established.