Condensation on the Outside of Double Glazing

Is there a problem when seeing condensation on the outside of double glazing? At certain times of the year it’s common to see moisture or condensation on even the newest windows. Some homeowners replacing old, single glazed and condensation windows may be surprised to see this on new windows. So what’s going on?

Condensation on the outside of double glazing. Here’s why it’s normal

Today’s modern double glazed windows come with very well insulated frames that are designed to be as energy-efficient as possible.  This energy efficiency has come about through changes in Building Regulations and government commitment over recent years. There’s an ongoing aim reducing the carbon footprint generally as well as heat loss through our homes. However, one unintended consequence of these improvements is the possibility of Condensation on the Outside of Double Glazing.

New windows today, whether in aluminium, pvcu or timber, you can be assured that they will all meet the latest window energy ratings and current standards for thermal efficiency.

condensation on the outside of double glazing

Modern replacement windows keep heat in and cold out.

Rest assured today’s energy-efficient A, B or C rated windows will help to retain heat in the home. At the same time they’ll work keeping the cold out.  One phenomenon that cannot be avoided is the presence of condensation on the outside face of your new windows.

If you do see condensation on the outside pane of your new windows, do not be concerned. The windows are simply doing their job. In simple terms, you will see surface condensation where the temperature on the external pane of glass is lower than the temperature outside. At the same time where the external temperature is higher than the temperature of the glass.

Seeing condenstation doesn’t always mean a problem.

However, if you see condensation between the two panes of glass on the inside of the sealed unit, this indicates that your double glazed unit has failed. It therefore needs replacement.  In most cases the hermetic seal that bonds the unit together and seals it will have failed. It’s therefore letting in air and moisture. It’s time to change the glass.

The presence of condensation on the inside of double glazed windows is not a fault. However in many cases just a consequence of how we live. Moisture from cooking, drying laundry inside, heating and even moisture when breathing. All these are factors causing condensation inside the home.

newly fitted windows in a modern house

What makes windows thermally efficient?

With aluminium windows this insulation is achieved by a sophisticated material called polyamide that creates thermally broken windows. 

In pvcu windows it is the multi chamber design within the frame that creates an insulated frame.  In timber windows, the solid nature of wood also acts as a great insulator.

The insulated frames available in aluminium, pvcu or timber windows are also complemented by very high specification double glazed units.  When double glazing first came about, the two panes of glass were simply standard glass. These came with a hermetic seal around the double glazed unit. Between the glass a normal air space.

Glass technology has now advanced significantly. Your glass now comprises either a Low Emissivity (low E) coating or K Glass. Then its enhanced by argon gas between the two panes of glass. Surrounding the unit a warm edge spacer bar, far superior to previous plastic or aluminium spacers. Instead of air space between the glass, there’s now Argon or Krypton gas.

Further advice about new windows and condensation

At certain times of the year, you will see condensation on the outside of your window.  This is a similar phenomenon to your car having condensation on seemingly dry nights or when only certain parts of your car are wet and others are dry.  Moisture will adhere itself to the first cold surface it finds.  The double glazed windows are actually doing their job of keeping the heat in and the cold out.

In most cases the condensation may only be visible on the centre area of your window. It’s seen less on the edges of the glass and where it meets the frame. This again is a sign that the window is performing as it should be.  The condensation will disappear as the external temperature increases during the day.

Should you be told about condensation before you sign up for new windows?

That will depend on your salesman.  The experience and knowledge of double glazing salespeople varies significantly from company to company. Many of the independent local double glazing firms will probably adopt a more professional approach to this issue.

Others keen to close a sale are unlikely to highlight any kind of “negative” with their product and will choose to say nothing.

Do new windows eliminate condensation?

Firstly, it is important to understand that all windows will condensate in some way.  You must never believe any double glazing salesperson that says “our windows will eliminate condensation”. This is untrue and completely misleading. New windows can never completely eliminate condensation.

What new double glazing will do is improve the current level of condensation on your old windows.  The thermal properties of modern aluminium frames and the high specification of modern double or triple glazing is superior to single glazed windows and non insulated frames.  All the modern aspects of today’s windows play a part in reducing condensation but nothing can eliminate it.

The presence of condensation is down to several factors but the main ones are how we live in our homes and what we do that causes moisture in the air.

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