Why does double glazing mist up?

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Misted Double Glazing – Blown Double Glazing – Condensation in Double Glazing

What Is It And Why Does It Happen?

Condensation on the inside of windows/doors occur when warm air vapour meets a cold surface area, as a result leaving a liquid residue on the window surface. This can be wiped away but if this builds up, over time mould can form. Condensation within your home can be controlled but it is when condensation forms between your double glazing glass that there is a problem.

Misted double glazed units are not only an eye-sore but are also a tell tale sign that there could be an underlying issue. It could also be a contributing factor to paying out more to heat your home as a result of your units not being properly insulated. It is good to understand the elements of what double glazing consists of to understand how it results in a misted, or a ‘blown’ or ‘failed’ unit, as it is also known in the industry.

How Is A Double Glazed Unit Made?

Double glazed units consists of two layers of glass separated by a continuous spacer bar which creates a layer of air. This layer of air acts as an insulating barrier. The spacer bar fitted between the two panes is filled with a desiccant to absorb any residential moisture within the cavity. This prevents condensation from forming between the panes. The spacer bar is then bonded to the glass and sealed with a primary and secondary sealant making the unit airtight.

double glazing

Why Does Condensation Appear?

1. Time

A common and unavoidable reason as to why your double glazing mists up is time. Over time the desiccant becomes saturated and can not absorb any more water vapour within the two panes. As a result this causes a build up of condensation to appear. Most double glazing suppliers offer a guarantee against their double glazing failing, on average anywhere between 5 to 10 years.

2. Poor installation

If your double glazing was fitted recently and has already began to mist up already, the seal could have been broken or compromised in some way. This could be the result of poor installation. You should contact your supplier who installed the window as this should be under guarantee for a certain period of time. When looking for a double glazing installer always go with an experienced and reputable company.

3. Chemicals

Over time harsh chemicals can allow water to seep through and break down the window sealant. You should always check the label before using any chemical products on your windows/doors.

Is There A Quick Fix?

There are the odd few glazing companies who offer a quick fix for removing the condensation from the cavity of the unit. This is a temporary measure and only available on a very limited amount of windows. With a broken down double glazed unit usually the only option is to replace it and get a guarantee for the future.

Getting A Replacement

If your double glazing is no longer covered under guarantee you can contact a glazing company to arrange for a replacement to be made. The frame will not have to be changed and it is just the glass unit itself that can be replaced. Price will vary depending on the size of the unit and also the glass specification. There are lots of glass options available today that are more energy efficient so options can be discussed with your glazier to give you maximum results.

Time For A Change

Your double glazing does not just have to be misted up for you to replace it. Double glazing can be replaced if it is damaged on one side or both, or if you simply want to upgrade it with something new and more energy efficient.

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For a free no obligation quote on any double glazing replacements please click here.


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