Should Double Glazing Ever Get Condensation


Whether they were there when you moved in, or you’ve had new dou­ble glaz­ing units installed your­self, it’s impor­tant to know what’s nor­mal and what isn’t when it comes to con­den­sa­tion. You may assume that if your win­dows aren’t clear all the time, then there’s some­thing wrong with them. This can some­times be the case, but only when talk­ing about con­den­sa­tion between the two panes.

To ensure you don’t con­tin­ue with failed dou­ble glaz­ing units (DGUs) or wor­ry unnec­es­sar­i­ly about a prob­lem’ which is com­plete­ly harm­less, check out our guide below. You may not need replace­ment dou­ble glaz­ing units after all!


In the cold­er months, you may notice that your DGUs have some dew or con­den­sa­tion on the out­side of the win­dow pane. This can be frus­trat­ing, espe­cial­ly if you want to see out, which, after all, is the point. This is a rather new prob­lem when it comes to dou­ble or triple glazed win­dow units, as it’s to do with how effi­cient they are.

The gov­ern­ment, in recent years, has set out guide­lines on how effi­cient new­ly installed win­dows have to be. This is all for the greater good; the more effi­cient your win­dows, the warmer your home will be. This will low­er your bills and help the envi­ron­ment as it uses less ener­gy. While this is all bril­liant, it does mean that much less heat is lost through your win­dows and there­fore they’re cool­er on the outside.

It’s this cool­er tem­per­a­ture that cre­ates the con­den­sa­tion. As the sur­face of the glass is cold, the air around it reacts with this tem­per­a­ture and con­dens­es, cre­at­ing mois­ture on the out­side. As the air warms up, the con­den­sa­tion will nat­u­ral­ly clear. This is an annoy­ing prob­lem, but one which is there for the right rea­sons. If you have con­den­sa­tion on the out­side of your dou­ble or triple glazed win­dows, then it’s like­ly to be because they’re doing the job they’re meant to do.

This doesn’t mean that, if you don’t have con­den­sa­tion on the out­side, your win­dows are not work­ing prop­er­ly. There are many dif­fer­ent fac­tors at play – so the fact your home faces a cer­tain direc­tion or is shad­ed by a big tree can make a dif­fer­ence. Rest assured that this type of con­den­sa­tion is noth­ing to wor­ry about. If it’s par­tic­u­lar­ly bad, there are some sprays on the mar­ket that you can use to water­proof’ your win­dows. Your local hard­ware store should have more information.

condensation on upvc windows


Hav­ing con­den­sa­tion on the inside of your win­dows can be a real­ly annoy­ing prob­lem. Not only can it pool on the win­dow sills inside your home, but it can also mean mould is more like­ly to grow on your walls and in oth­er areas. Once mould and damp have tak­en hold in your home, it’s very hard to get rid of and can, in extreme cas­es, cause health problems.

So is it the fault of the win­dows? Some homes tend to get con­den­sa­tion on the inside when new DGUs are fit­ted, and this is assumed to be the fault of the win­dow. How­ev­er, this is anoth­er prob­lem which may have been exac­er­bat­ed by the fact that the win­dow is sim­ply very efficient.

Lots of water vapour is pro­duced inside your home every day and there’s not a lot you can do to pre­vent that. Breath­ing, dry­ing clothes, cook­ing, show­er­ing – these activ­i­ties all release water mol­e­cules into the air. When this warm, damp air hits a cold sur­face (such as a win­dow), it turns into liq­uid water, which forms the con­den­sa­tion. The only way you can stop this from hap­pen­ing is ventilation.

This issue is a bit of a catch-22 sit­u­a­tion. In order to ven­ti­late your home, you need to allow air to move in and out. This defeats the object of effi­cient DGUs which are there to keep the heat in, but it’s the sheer effi­cien­cy of the win­dows which may be caus­ing the mois­ture build-up in the first place. Old­er or poor­ly-fit­ted win­dows will let air in and out all the time, which means they may not suf­fer from con­den­sa­tion so bad­ly. How­ev­er, they will also make your home cold­er and more expen­sive to heat.

The best solu­tion is to open your win­dows when you cook and when you take a bath or show­er, dry your win­dow sills if you see mois­ture on them and open your win­dows to ven­ti­late your home for a lit­tle while each day. Try to con­tain steam to one room only and leave a win­dow open until this has cleared – this should stop mois­ture from trav­el­ling to oth­er areas of your home. There’s unlike­ly to be any­thing wrong with your win­dows if this is hap­pen­ing, so don’t order those replace­ment DGUs just yet!


If the con­den­sa­tion on your win­dows is not on the inside or the out­side, but between the two (or three) panes where you can’t get to it, then you may have a prob­lem. The fact that mois­ture is build­ing up inside the win­dow means that the seals have stopped doing their job properly.

The seals keep fluc­tu­at­ing tem­per­a­tures from affect­ing the win­dow by cre­at­ing a com­plete­ly air­tight envi­ron­ment between the panes. When the seals degrade or are dam­aged through age or wear & tear, the con­stant envi­ron­ment between the glass is com­pro­mised. This means that fluc­tu­a­tions in tem­per­a­ture (as night turns into day, for exam­ple) can cause mois­ture to col­lect in the space.

condensation on old windows inside

The only way to have this rec­ti­fied is to have your dou­ble glaz­ing units replaced. In most cas­es your win­dow frames (if good qual­i­ty) can stay where they are – it’s just the glass that will need replac­ing. Many dou­ble (or triple) glaz­ing fit­ters will put a long guar­an­tee on DGUs (Evan­der have a 5‑year guar­an­tee on dou­ble glazed units), so check to see if they’re still under war­ran­ty before order­ing replace­ments. When con­den­sa­tion builds up between your win­dow panes, it means that your home is no longer as effi­cient as it was, and you may notice your bills ris­ing, par­tic­u­lar­ly in the winter. 

The soon­er you can order replace­ment dou­ble glaz­ing units the bet­ter. If you’re wor­ried about your win­dows and want to speak to us, then feel free to give us a call on 0345 145 0130, email us on enquiries@​evander.​com or use the con­tact form below.

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