Condensation on double glazed windows is not common but it can happen.
The Australian Glass and Window Association (AGWA) key message on condensation states:
- “Double glazed windows create warmer interior glass surfaces, reducing frost and condensation.”
- “Glass with a Low-E coating on the internal surface can promote condensation more readily than uncoated glass.”
You might be surprised to read that second point — but don’t be alarmed.
The Low-E coating on the internal surface of your double glazed windows helps to keep warm air inside your home, thus raising the temperature on the internal surface relative to the exterior surface of glass. And if the exterior surface of glass is cooler than the outside air temperature you might notice exterior window condensation.
In this blog, we explore the causes of condensation on double glazed windows and discuss effective ways to address this issue.
Condensation on Double Glazed Windows
There are three places you are most likely to notice condensation on your double glazing:
1. Interior condensation
Interior condensation can be observed as steamy windows, or water droplets on the glass surface inside your home, and can be wiped away. It occurs when there are high levels of interior humidity in your home.
Limit interior window condensation by opening your windows slightly to improve ventilation and reduce interior humidity.
Read more in our blog, Getting the Drop on Interior Window Condensation.
2. Exterior condensation
Exterior condensation can be observed as fogginess, or water droplets on the glass surface facing the outside of your home and can be wiped away. It occurs when the temperature of the exterior surface of the glass is cooled below the temperature of the outside air.
To limit exterior window condensation, create a clear area between your garden plants and your windows to promote better air circulation around your outside windows .
3. Condensation inside the air gap
If you notice condensation between the glass panes where you cannot reach it to wipe it away, there could be an issue with the airtight seal on your Insulated Glazing Unit (IGU).
To understand how condensation can form between the air gap in Double Glazing we need to look at how an Insulated Glazing Unit (IGU) is constructed.
IGUs work by creating a sealed air or gas vacuum between two panels of glass. The space between the panes of glass can have a significant effect on heat transfer both into and out of your home, so it’s important that this is airtight.
There is also a spacer bar often filled with desiccant that separates the two pieces of glass and serves to absorb moisture, preventing condensation from creeping in.
If you notice condensation between the two panes of glass, it could mean that the seal which protects the inside of the IGU has been damaged, allowing moist air from outside to enter.
Do I need to replace my double glazing due to condensation?
Condensation on the interior and exterior surfaces of your double glazing is normal, but if you notice moisture buildup between the panes of glass inside the air gap you may need to consider replacing your double glazed windows. Depending on the extent of the broken seal, an Insulated Glazing Unit can still function but it won’t be as effective as an IGU with an intact seal.
Condensation inside the air gap can also affect visibility through the window as it fogs up and cannot be wiped away like interior or exterior window condensation.
If your double glazing is still under warranty, you should contact the manufacturer to check what recourse is available to you.