Window Condensation
If you've noticed water droplets forming on your windows — especially first thing in the morning in winter — you're not alone. Condensation is one of the most common questions we get from Melbourne homeowners, and it's completely understandable why it causes concern.
The good news is that condensation isn't always a sign of a problem. The not-so-good news is that sometimes it is. Let's break it down.
What Actually Causes Condensation?
Condensation forms when warm, moist air meets a cold surface. Your window glass — particularly in winter — can be much colder than the air inside your home, and when that warm air hits the cold glass, the moisture in it turns to water droplets.
Think about a cold drink on a hot day. Same principle.
Inside Condensation vs Outside Condensation
Where the condensation appears matters a lot.
Condensation on the inside of your window
This is the most common type and is usually a ventilation issue rather than a window problem. It tends to happen in rooms with high moisture levels — bathrooms, kitchens, laundries — or in homes that are well-sealed without enough airflow.
It's more of a comfort and mould-risk issue than a structural one, and the fix often comes down to improving ventilation rather than replacing windows.
Condensation on the outside of your window
This one actually sounds alarming but is usually a good sign. It means your double-glazed windows are doing their job — the outer pane is staying cold because the insulation layer inside is working, so moisture from the outdoor air condenses on it.
You'll often see this in spring and autumn when overnight temperatures drop and mornings are warm. It clears on its own as the day warms up.
Condensation between the panes of a double-glazed window
This is the one to watch out for. If you're seeing fog or water droplets trapped between the two panes of glass, it means the seal on your double-glazed unit has failed. Moisture has gotten in where it shouldn't be.
This won't fix itself, and it does affect the thermal performance of the window. It's worth getting it assessed.
Is It a Sign My Windows Need Replacing?
Not necessarily — but it can be. Here's a rough guide:
- Inside condensation in a well-ventilated room — worth getting your windows checked; single glazing or draughty frames may be contributing
- Outside condensation — usually fine, nothing to worry about
- Condensation between the panes — the sealed unit has failed and likely needs replacing
- Condensation plus visible rot, rust or warping on the frame — your windows may be past their best
What Can You Do About It?
Depending on the cause, the solutions vary:
- Improve ventilation — open windows when cooking or showering, use exhaust fans, and consider a whole-home ventilation strategy if the problem is widespread
- Check your window seals and frames — draughts and gaps allow moisture in and affect thermal performance
- Upgrade to double glazing — significantly reduces inside condensation by keeping the glass surface warmer
- Replace failed sealed units — if condensation is between the panes, the unit itself needs to go
When Should You Call Someone?
If the condensation is persistent, widespread, or you're seeing it between the panes, it's worth getting a professional opinion. What looks like a moisture problem can sometimes point to failing frames, inadequate sealing or glazing that's simply past its useful life.
If you're not sure what you're looking at, we're happy to come out, take a look and give you an honest assessment — no pressure, no jargon. Contact out team to find out how.