How to Stop Condensation on Windows

Do you ever wake up, open your blinds, and notice a foggy film on your windows? That’s condensation, and while it might seem harmless, it can actually signal that your windows aren't performing as well as they should. Let's explore what causes condensation and how the right windows can help keep your home comfortable, efficient, and free from moisture-related problems.

What causes condensation on windows?

Condensation on windows happens when warm, moist air meets a cold surface. 

The air around us always contains some level of water vapour. This is known as ‘relative humidity’, which is measured on a scale from 0 to 100%. At 100% relative humidity, the air is fully saturated and can't hold any more moisture. This is the dew point, and it’s when condensation occurs and water vapour turns into liquid on cooler surfaces. Warm air holds more moisture than cold air. 

Simple example? Think of it like taking a cold drink outside on a hot day. Water droplets form on the outside of the glass because the warm, humid air hits the cold surface and can't hold its moisture anymore so droplets appear. The same thing happens with your windows, especially overnight when outdoor temperatures drop while your home stays warm inside from cooking, showering, or heating.

Why should we pay attention to condensation on windows?

While a bit of foggy glass might seem like a minor inconvenience, regular condensation can lead to more serious issues such as mould and mildew growth, decay of building materials, potential health problems from poor air quality, and damage to window frames, walls, and surrounding areas.

This is particularly common in high-moisture areas like bathrooms, but it can happen throughout your home. Activities like cooking, showering, drying clothes, and even just breathing add moisture to your indoor air. Without window condensation prevention, this moisture buildup can create an unhealthy living environment.

What are the regulations around condensation?

In Australia, the National Construction Code (NCC) provides guidelines for managing condensation, safety, and health based on different climate zones. Australia is divided into 8 climate zones, each with different condensation risks. It’s important you understand each zone, so your home meets the requirements to prevent condensation.

City	Local Climate Zones	Summer season risk	Winter season risk
Cairns	Hot humid summer, warm winter	If air-conditioned, high risk of condensation forming on cold surfaces within the structure	Minimal risk
Brisbane	Warm humid summer, mild winter	If air-conditioned, high risk of condensation forming on cold surfaces within the structure	Some risk
Alice Springs	Hot dry summer, warm winter	Minimal risk	Some risk
Dubbo	Hot dry summer, cool winter	Minimal risk	High risk
Perth / Adelaide / Sydney	Warm temperate	If air-conditioned, high risk	High risk
Melbourne	Mild temperate	Low risk	High risk
Hobart	Cool temperate	Low risk	Certain risk
Alpine Regions	Alpine	Certain risk	Certain risk

In hot humid climates, moisture tries to move from outside to inside. In cool climates, moisture moves from inside to outside. In temperate climates, it flows in both directions. Understanding your local zone and how moisture tends to move will help you determine your condensation risk, and how you build a house in an effective manner to combat it.

How to prevent condensation on windows

The best approach towards minimising condensation on windows is controlling water vapour in your home. Here are seven practical tips to reduce condensation:

1. Keep internal surface temperatures above the dew point by installing proper insulation, insulated glazing units, and quality window frames

2. Use insulated blinds over windows for an extra layer of protection

3. Ensure air can circulate behind furniture placed against external walls

4. Avoid thermal bridges (pathways for heat transfer) by installing thermal breaks between metal frames and cladding

5. Include a ventilated cavity within wall spaces to allow moisture to escape

6. Consider installing mechanical ventilation heat recovery systems

7. Use appropriate building membranes to control air and water vapour movement

   
   

Building membranes are materials used to control how air and water vapour move through a building. Different types of membranes allow different levels of water vapour to pass through, which is known as permeability. This is measured by how much vapour can move through a material under pressure. There are three main types:

• Vapour-impermeable membranes – block water vapour completely.

• Vapour-permeable membranes – let water vapour pass through.

• Smart membranes – adjust how much vapour they let through based on temperature and humidity.

Depending on the climate zone, they can be placed to keep walls, windows, and areas above dew point temperature.

How to reduce condensation on windows

The windows you choose play a crucial role in condensation control. Here's what to look for:

Framed windows made from both timber and aluminium, such as Miglas' flagship AliClad range, provide excellent insulation and help to maintain warmer indoor surface temperatures as well as minimise moisture build-up.

When it comes to glass, options like double or triple glazing, low-emissivity (Low-E) coatings, and argon-filled units are all ideal. These features reduce heat loss and reflect warmth back into the room, keeping interior glass surfaces warmer and less prone to condensation.

These features work together to keep interior surfaces above the dew point temperature, preventing moisture from condensing on your windows and doors.

Invest in long-term comfort 

The right windows will help maintain a comfortable indoor environment year-round, reduce energy costs, prevent moisture problems, and protect your home's structure from damage. When you consider that premium windows can last 50+ years, the investment makes sense for both immediate comfort and long-term home protection. 

By understanding how to stop condensation and choosing the right windows for your climate zone, you can create a healthier, more comfortable living environment that stands the test of time. At Miglas, we know our high-performance double-glazed windows and AliClad frames are making all the difference for our customers. If you’re interested in learning more about which is best for you, contact us to get started.