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Double Glazing Condensation

Category: Blog, Tips and Tutorials

The benefits of double glazed windows are well documented: they help keep your house warmer in winter and cooler in summer; they can save you money on your energy bill; and by choosing the right combination of glass options, they can also help with noise reduction.

A skyline full of beautiful orange and blue hues as the sun rises over the city, as viewed through a window covered in droplets of condensation

But what about double glazing condensation?

To quote the Australian Glass and Window Association (AGWA):

  • “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 is likely doing its job by keeping 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.

Let’s take a closer look at the different types of double glazing condensation.

A typical house may produce in excess of 20L of water vapour per day!

Condensation inside, outside, or in-between double glazing

There are three places you are most likely to notice condensation on your double glazed windows and doors:

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.

We talk about how to prevent interior window condensation in our blog, Getting the Drop on Interior Window Condensation.

Quick Tip: Open windows slightly to improve ventilation and reduce interior humidity.

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.

Quick Tip: Promote better air circulation around your outside windows by creating a clear area between your garden plants and your 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).

Editor’s Note: IGU stands for Insulated Glazing Unit and DGU stands for Double Glazing Unit. They both refer to the same thing, double glazing, and are often used interchangeably.

Condensation between the glass panes of double glazed windows

To understand how condensation can form between the air gap in Double Glazing we need to take a look at how a Double Glazing Unit (DGU) is constructed.

Double Glazed Units (DGU) 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 means that the seal which protects the inside of the DGU has likely been damaged, allowing moist air from outside to enter.

Do I need to replace my double glazing?

Depending on the extent of the broken seal, a Double Glazing Unit can still function but it won’t be as effective as a DGU 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.

For peace of mind, Jason Windows offer a 10 Year Structural Warranty on all Jason products.


About the Author

Dempsey O'Callaghan - Service Manager

Dempsey O’Callaghan is the Service Manager at Jason Windows. Our Servicing and Spare Parts Team include 13 specialised Service Technicians fully trained on over 150 unique service tasks which may arise in the course of their day. It takes several years to master all of the facets of our Service Technician roles and many of our Service Technicians are also qualified glaziers. Our Servicing Support Team work behind the scenes to ensure that an average of 100 jobs are booked in and scheduled each day.


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