Why Does Double Glazing Mist Up?

Double glazing is formed from two panes of glass sealed together, with a gap left between them, to form a double glazed unit. The air trapped inside the window (sometimes gas, depending on the units rating), creates an insulating barrier that keeps heat in. It’s when this seal on the glass fails that condensation gets into the window, resulting in the misting. There are a few reasons the seal can break, although usually due to the age of the window and how it was manufactured (the seals don’t last forever). How it was originally fitted and any chemical cleaning material used on the window can also affect its life span.

Misting on the Outside of the Window?

This is a natural occurrence and not an issue with the glass or double glazing unit. It is not due to your double glazed window failing as described above. This situation occurs, mainly in Spring and Autumn, when the glass temperature falls to a low level at night, with the moisture of a heavy morning dew condenses against the cold surface of the glass. Contemporary window technology has resolved this in most cases, our stocked panes are more thermally efficient than in the past. However, you do not need to change the glass or frame as this is a natural phenomenon.

Does it Affect My Energy Bill?

The Energy Efficiency Agency states that the average household will save £165 a year on energy bills if you have B-Rated windows fitted. A B-Rated Window (or indeed A-Rated) is not dependent on the frame, but the type of glass you have fitted. If the seal on your window has broken, you are losing the insulation the original window provided and more heat will escape, leading to a higher heating bill.

Do I Need To Change The Window Frame?

This is a common misconception. As a misted-up window is due to the seal on the glass, which is a separate component from the frame. If the frame is ok, just replace the glass unit. At this stage you also have the option of upgrading to an A-rated unit, further increasing energy savings.

Does Inserting Warm Air Solve the Problem?

No. If the window mists due to a faulty seal, blowing warm air in to clear the mist is only a temporary solution. Unless the seal is replaced, condensation will still get into the window. Having this type of repair may well appear to ‘fix’ the window for a few months, it will never truly fix the window and you will have to repeat the repair several times over the year to clear the misting of the window.

Can I Repair the Unit Myself?

Any work done would need to involve replacing the seal to solve the problem. Without professional installation, you may contravene building regulations, which could issues when selling your home. Work carried out by a reputable company will also come with a guarantee for peace of mind. 

We Recommend…

We recommend replacing the unit to solve misting and maintain the energy efficiency of your home. Quick fixes will cure the misting short term, but your heating bills will be increased until resolved. A guarantee of workmanship will protect you should the unit have issues in the future.