Waking up to water running down the inside of your bedroom windows is more than an annoyance. If it happens regularly, it can damage timber reveals, lift paint, encourage mould and make a Melbourne home feel colder than it should. To reduce window condensation, you need to manage the moisture produced inside the house and improve the temperature of the glass surface where that moisture collects.
Condensation is common through Melbourne’s cooler months, particularly in older homes with single glazing, limited ventilation and gas heating. The good news is that most properties can improve it with a practical mix of daily habits, ventilation upgrades and better-performing windows.
Why window condensation forms
Indoor air always holds some moisture. Cooking, showers, drying laundry, breathing and even pot plants all add water vapour to the home. When warm, moist indoor air reaches a cold window pane, it cools quickly. Once it reaches its dew point, the moisture turns into droplets on the glass, frame or surrounding wall.
The window is not creating the moisture. It is simply the coldest visible surface in the room, so it reveals a moisture problem that may otherwise go unnoticed. On very cold mornings, condensation can also occur on aluminium frames if they are not thermally broken, as aluminium transfers heat readily.
A small amount of condensation on the outside of high-performance double glazing can be normal. It can mean the outer pane is staying cold because the unit is holding warmth inside. Condensation on the room-facing side is the issue that needs attention, especially when it appears most days or pools on the sill.
Start by reducing moisture at the source
Before changing windows, look at where water vapour is coming from. This is often the fastest and lowest-cost way to make a difference.
Run exhaust fans while showering and for at least 15 to 20 minutes afterwards. A fan that vents outside is far more effective than one that simply recirculates air. Keep the bathroom door shut while showering, then open windows or the door once the steam has cleared.
In the kitchen, use the rangehood whenever you cook, particularly when boiling pasta, simmering sauces or using multiple burners. A ducted rangehood that discharges outdoors removes substantially more moisture than a recirculating model. Keep saucepan lids on where practical.
Drying clothes indoors is a major contributor to winter condensation. Use an outdoor line whenever weather allows, or run a vented dryer correctly. If indoor drying is unavoidable, keep it in one well-ventilated room with the door closed and a window slightly open. A dehumidifier in that room can also be worthwhile.
Unflued gas heaters release water vapour into the air as they operate. They may warm a room quickly, but they can worsen condensation and indoor air quality. If you use one, improve ventilation and consider whether a reverse-cycle split system is a better long-term heating option.
Ventilate without making the house freezing cold
It can feel counterproductive to open windows on a cold Melbourne morning, but controlled ventilation removes humid air before it settles on cold glazing. You do not need to leave every window wide open all day.
Open windows for a short cross-flow period after showers, cooking and waking up. Even 10 minutes with openings on opposite sides of the home can replace a large volume of moist air. Where security and layout permit, leave selected awning windows slightly open during the day. Awning designs are particularly useful because they can provide airflow while helping shield the opening from light rain.
Bedrooms need attention because people generate moisture overnight. If bedroom windows are heavily wet each morning, try opening the window after getting up, keeping wardrobe doors slightly ajar and avoiding clothes drying nearby. Condensation inside wardrobes can lead to mould before you see it on walls.
For tightly sealed renovated homes, passive ventilation alone may not be enough. An appropriately sized extraction system, ceiling fan or balanced mechanical ventilation solution may be justified, especially in bathrooms without external windows and high-occupancy homes.
Improve the glass temperature with double glazing
Single-glazed windows have one thin pane separating warm indoor air from winter conditions outside. The inner glass surface can become very cold, which makes condensation far more likely. Double glazing creates an insulating gap between two panes, keeping the internal pane warmer and reducing the conditions that cause moisture to settle.
For homeowners replacing ageing windows, this is often the most effective permanent upgrade. Double-glazed aluminium windows can also improve thermal comfort, reduce outside noise and help cut heat loss. The benefit is not just fewer wet panes. A warmer internal surface makes rooms feel more comfortable at the same thermostat setting.
However, glazing is not a standalone cure. A home with very high indoor humidity can still experience condensation on double glazing, particularly around frames or in bathrooms. Treat the moisture source and ventilation as part of the same job.
When comparing replacement windows, check the full system rather than the glass alone. Frame design, seals, drainage paths, installation quality and opening configuration all affect real-world performance. For exposed sites or projects close to busy roads, it is also worth considering watertightness, acoustic requirements, security and BAL requirements alongside thermal performance.
Check seals, drainage and installation details
Water on the room side of the glass is typically condensation. Water appearing between panes in an insulated glass unit can indicate a failed seal. Water coming in during rain points to a different issue again, such as flashing, external seals, drainage or installation.
Inspect windows for damaged seals, blocked weep holes and deteriorated perimeter caulking. Aluminium window systems rely on drainage channels to direct incidental water back outside. Do not seal over weep holes or block tracks with debris, as this can stop the system functioning as designed.
Replacement projects need accurate measurements and suitable reveal, flashing and sill details. Fitting a high-performance window into an unaddressed wall opening can leave cold bridges and gaps that undermine the result. Builders and renovators should also coordinate window installation with insulation, wall wraps, cladding and internal lining works rather than treating glazing as a last-minute item.
Use heating consistently, not just at full blast
A room that swings from very cold to very warm can produce more condensation than one kept at a moderate, stable temperature. Reverse-cycle heating is generally an efficient option because it warms indoor surfaces as well as the air over time. It does not add moisture to the room like an unflued gas heater.
Avoid pushing furniture tightly against external walls and windows. Leaving a small air gap allows warm room air to circulate and helps prevent hidden damp patches. Heavy block-out curtains can improve comfort at night, but open them in the morning to let air reach the glass and dry any light moisture.
If you use a dehumidifier, size it for the room or area you are treating and empty or plumb it correctly. It can be particularly useful in bedrooms, laundries and apartments where opening windows is limited. It is a management tool, though, not a substitute for fixing persistent leaks, inadequate extraction or poorly performing glazing.
When condensation means a bigger building issue
A few droplets after a hot shower are usually manageable. Persistent water across several windows, mould on walls, a musty smell or damp carpets call for a closer look. The cause may be insufficient subfloor ventilation, a roof or plumbing leak, rising damp, poor insulation, overcrowding or a heating system that is adding too much moisture.
For new builds and substantial renovations, plan for moisture control early. Select window and door systems with the right glazing for the orientation and local conditions, include effective kitchen and bathroom extraction, and make sure insulation and air-sealing work are properly detailed. Fast window availability is valuable on a construction programme, but correct specification matters just as much.
For Melbourne replacements, WINDOWS DOORS INSTOCK & REPLACEMENT can assist with practical aluminium window options, including double-glazed configurations and custom sizes suited to renovation and building work.
The aim is not to make a home completely airtight or eliminate every drop of moisture. It is to keep humidity under control, maintain warmer internal surfaces and deal with water before it becomes mould or damage. Start with ventilation and moisture sources, then use better glazing where the existing windows are holding the home back.