Why Do My Windows and Doors Have Condensation?

Dif­fer­ent types of con­den­sa­tion have dif­fer­ent effects on your prop­er­ty, but they all may have an adverse effect on your prop­er­ty over time. In this blog, we’ll look at the caus­es of con­den­sa­tion and dis­cuss what you can do about each of them.

Hav­ing con­den­sa­tion present doesn’t nec­es­sar­i­ly mean that you’ll need to replace your dou­ble glazed win­dows or doors — in fact, there may be a much cheap­er and sim­pler solu­tion. Read on to find out what type of con­den­sa­tion you have and what you should be doing about it.

The dif­fer­ent types of condensation

There are three dif­fer­ent types’ of con­den­sa­tion, although they are only dif­fer­ent because of where they are sit­u­at­ed. Con­den­sa­tion is caused when water vapour col­lects on cold­er sur­faces. This cre­ates a misty appear­ance, which can turn into a cov­er­ing of larg­er water droplets in more severe cas­es. As these water droplets become heav­ier, they run down the win­dow, and some house­holds may have noticed small pud­dles on their win­dow sills at cer­tain times of the year as a result. The three types of con­den­sa­tion we will be talk­ing about are:

  • Inner con­den­sa­tion, which col­lects on the inside of your windows
  • Out­er con­den­sa­tion, which col­lects on the out­side of your windows
  • Gap con­den­sa­tion, which col­lects between the two panes of glass on dou­ble-glazed win­dows and doors

Of course, if your win­dows or doors are sin­gle-glazed, you’ll only have either out­side or inside con­den­sa­tion. If you have triple-glazed win­dows, you may expe­ri­ence gap con­den­sa­tion in one or both of the spaces between the glazed pan­els, but this is unlike­ly if the unit has not been obvi­ous­ly damaged.

Inside con­den­sa­tion is the most com­mon, and out­side con­den­sa­tion is a rel­a­tive­ly new prob­lem, albeit a harm­less one. Unfor­tu­nate­ly, fur­ther prob­lems can arise if you are expe­ri­enc­ing inside or gap con­den­sa­tion, which we explain in more detail below.

misted up double glazing

Why con­den­sa­tion forms on win­dows and doors

Know­ing why the con­den­sa­tion forms on your glaz­ing can help you to solve the prob­lem quick­ly with­out too much expense. Each type of con­den­sa­tion is caused by some­thing different:

Inner con­den­sa­tion is caused by an over­abun­dance of water vapour in the air inside your home. When the out­side of the win­dow gets cold, the warm, damp air hit­ting the win­dow on the inside will turn into con­den­sa­tion. You are like­ly to notice this hap­pen­ing more when you are cook­ing or show­er­ing, as well as dur­ing the autumn and win­ter when the inside of your house is warmer than outside.

This type of con­den­sa­tion is very com­mon on sin­gle-glazed pan­els and can eas­i­ly form on more effi­cient dou­ble-glazed win­dows and doors too. You may be sur­prised at the amount of water vapour that your house­hold gen­er­ates in a 24 hour peri­od. Show­er­ing, dry­ing clothes and cook­ing are all obvi­ous sources of inner con­den­sa­tion, but did you know you cre­ate water vapour by sim­ply breath­ing and going about your day? Approx­i­mate­ly 15.7 litres of water vapour is pro­duced a day by the aver­age four-per­son house­hold, accord­ing to damp spe­cial­ist Peter Mac­Don­ald. With­out prop­er ven­ti­la­tion, this can cause con­den­sa­tion and damp problems.

Out­er con­den­sa­tion is caused by the same reac­tion, just the oth­er way around. It affects prop­er­ties which have very effi­cient win­dows and doors and is caused by warmer air hit­ting the out­side of your win­dow. This is most like­ly to hap­pen in the morn­ing, as the sun is com­ing up and could hap­pen in any sea­son, depend­ing on the con­di­tions. This does not mean that the inside of the home is cold in com­par­i­son — it sim­ply means that the glaz­ing is so effi­cient that the out­er pane is much cold­er than the inner one, hence the con­dens­ing reac­tion with the air outside.

Gap con­den­sa­tion hap­pens as a result of the dou­ble-glazed unit fail­ing. All dou­ble-glazed win­dows and doors have a small gap between the two panes. This space is filled with a harm­less gas, which cre­ates an insu­lat­ing lay­er of air, thus help­ing to keep the warm air in and the cold air out. If the seal has bro­ken around the edges of the unit, the insu­lat­ing gas will escape and con­den­sa­tion will occur between the panes. This can, in some very extreme cas­es, to cause the inner space to fill with water.

condensation forming on the inside

Relat­ed issues

Both inside and gap con­den­sa­tion cause prob­lems and should be addressed as soon as you can to pre­vent fur­ther issues.

Gap con­den­sa­tion with­in your dou­ble-glazed units seri­ous­ly reduces the ener­gy effi­cien­cy and will have a notice­able effect on the tem­per­a­ture in your house­hold, not to men­tion your ener­gy bills. If you have more than one failed unit, you could find that your heat­ing bills are high­er and that you expe­ri­ence more issues with damp and con­den­sa­tion on the inside of the win­dow, due to the decrease in ener­gy efficiency.

Inside con­den­sa­tion can cause damp or mould in the worst affect­ed rooms. This usu­al­ly man­i­fests as green or white patch­es with dis­coloura­tion of paint­work and/​or peel­ing wall­pa­per, usu­al­ly in the upper cor­ners of the affect­ed room. You may also be able to smell the damp as it can emit a rather musty odour.

Of course, you may not have issues with mould yet, but if you com­mon­ly find con­den­sa­tion on the inside of your win­dows and doors, it’s like­ly you’ll expe­ri­ence some mould or mildew at some point. If the con­den­sa­tion is leav­ing pud­dles of water on your win­dow sills or floor­ing, you should address the issue as soon as you can. Mould and damp are not just unsight­ly but can pose seri­ous prob­lems to your health such as res­pi­ra­to­ry issues and aller­gic reac­tions, so get­ting it sort­ed soon­er rather than lat­er is paramount.

Please note that ris­ing damp (where a wall is notice­ably damp at the bot­tom – the damp may rise fur­ther up the wall over time) is not caused by mois­ture inside the home but mois­ture ris­ing up through the build­ing mate­ri­als from the ground. If you are expe­ri­enc­ing this prob­lem you will need to con­sult a professional.

Out­side con­den­sa­tion does not cause prob­lems with your prop­er­ty but may be frus­trat­ing. This is under­stand­able – the point of win­dows is to be able to see out of them and if con­den­sa­tion on the out­side is pre­vent­ing you from doing so, your effi­cient win­dows and doors may feel like a waste of money.

Con­den­sa­tion solutions

Thank­ful­ly, there are things you can do to reduce all three types of con­den­sa­tion, or even solve the prob­lem alto­geth­er. The ease and expense vary depend­ing on the type and sever­i­ty of the con­den­sa­tion in your home.

opening window to reduce condensation

For inside con­den­sa­tion, there is no quick fix. Instead, tack­ling it is an ongo­ing issue and will mean adapt­ing your lifestyle in some key areas. First­ly, ensur­ing your home is well ven­ti­lat­ed is para­mount, as this will allow water vapour to escape and fresh air be drawn into your home. Open a win­dow when you’re cook­ing and when you’re in the bath or show­er — try to do this all year round if you can. When you first spot con­den­sa­tion, open the win­dow (or a win­dow in the same room) a small amount and wipe up any mois­ture which has already formed with a towel.

Installing a dehu­mid­i­fi­er can also make a big dif­fer­ence, and it may sur­prise you just how much water is drawn from the atmos­phere in a bad­ly affect­ed room. Make sure you research the best size and pow­er for your needs before pur­chas­ing a dehu­mid­i­fi­er, as there is a wide range of options available.

indoor dehumidifier

Dry­ing cloth­ing inside the home is one of the worst caus­es of water vapour, so aim to dry your clothes out­side or tum­ble-dry them where pos­si­ble. Where this is not an option, ensure your win­dows are open and try not to put out too many wet clothes at once. It’s not a good idea to dry clothes in a room which does not get a lot of sun­light due to the direc­tion it faces or because it is in shad­ow, as this can exac­er­bate issues with mould, so when indoors is your only option, aim to dry your cloth­ing in sun­nier, well ven­ti­lat­ed rooms.

drying clothes outside

Out­side con­den­sa­tion should clear on its own and should not stay for very long. How­ev­er, the sever­i­ty of it can vary depend­ing on how much sun your home gets. If out­side con­den­sa­tion is becom­ing a prob­lem, your local DIY shop is like­ly to stock a water­proof­ing spray which can be applied to the out­side of the glass to ensure the con­den­sa­tion can­not stick’ to the sur­face as eas­i­ly. Check with who­ev­er installed your win­dows to ensure this does not affect any war­ran­ty you may have.

Gap con­den­sa­tion can only be solved by hav­ing the unit replaced, which may be under war­ran­ty or cov­ered in your home insur­ance pol­i­cy. If not, you don’t have to wor­ry about replac­ing the whole win­dow or door as the glazed unit can be removed and a new one can be fit­ted into the same frame. Dou­ble glazed units should not fail like this but it does hap­pen, either through gen­er­al wear & tear or acci­den­tal damage.

gap condensation on inside of window

Out­side con­den­sa­tion should clear on its own and should not stay for very long. How­ev­er, the sever­i­ty of it can vary depend­ing on how much sun your home gets. If out­side con­den­sa­tion is becom­ing a prob­lem, your local DIY shop is like­ly to stock a water­proof­ing spray which can be applied to the out­side of the glass to ensure the con­den­sa­tion can­not stick’ to the sur­face as eas­i­ly. Check with who­ev­er installed your win­dows to ensure this does not affect any war­ran­ty you may have.

Gap con­den­sa­tion can only be solved by hav­ing the unit replaced, which may be under war­ran­ty or cov­ered in your home insur­ance pol­i­cy. If not, you don’t have to wor­ry about replac­ing the whole win­dow or door as the glazed unit can be removed and a new one can be fit­ted into the same frame. Dou­ble glazed units should not fail like this but it does hap­pen, either through gen­er­al wear & tear or acci­den­tal damage.

Win­dow & door best practice

Look­ing after your win­dows and doors and ensur­ing that they are kept up to date where effi­cien­cy is con­cerned is impor­tant in many ways, and can also help to tack­le con­den­sa­tion on a long-term basis. If you have very old doors and win­dows, they will not be as effi­cient­ly glazed as new­er ver­sions. The man­u­fac­ture of glaz­ing has come so far in recent years that you may be sur­prised at what a dif­fer­ence new dou­ble-glaz­ing and effi­cient frames can make to your com­fort and your ener­gy bills.

Keep­ing your win­dows and frames clean and free of debris is also impor­tant, as a build-up of grime could cause water to gath­er where it shouldn’t due to blocked drainage holes. This, in turn, can accel­er­ate the wear and tear on the unit, caus­ing it to fail.

If you’re inter­est­ed in a quote for new­er and more effi­cient win­dows or doors, or if you believe you have a failed dou­ble- or triple-glazed unit, please do get in touch with us on 0345 145 0130 or by using our con­tact form. You can view our range of win­dows and doors on the site by using the top nav­i­ga­tion bar.

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