# Window condensation



## bofarr01 (13 Oct 2005)

All,
In the last week or so (coinciding with colder weather?) we have noticed a lot of condensation on the insides of windows on our standard 3-bed semi. For some reason, it's far worse than we've ever seen it.

What exactly causes condensation and what can be done to minimise it?

thanks,
B


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## ClubMan (13 Oct 2005)

bofarr01 said:
			
		

> What exactly causes condensation


Warm moist/humid air meeting a cold barrier such as a cold window causing the airborne moisture to condense was water droplets.



> and what can be done to minimise it?


Double glazing. Dehumidification. Ventilation etc. See here.

Note that if you get significant condensation with double glazed windows then they are not doing their job properly (e.g. the seal on the double glazed units may be broken undermining the thermal barrier between the panes).


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## Carpenter (13 Oct 2005)

> Note that if you get significant condensation with double glazed windows then they are not doing their job properly (e.g. the seal on the double glazed units may be broken undermining the thermal barrier between the panes).


However note that double glazed units should last 10 years at least. Increase your heating and ventilation, don't dry clothes indoors (at least not excessively) and make sure any permavents are open to allow fresh air to enter habitable rooms. Keep bathroom doors closed when showering/ running a bath.


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## ClubMan (13 Oct 2005)

Carpenter said:
			
		

> Increase your heating and ventilation


Doesn't this conflict with the standard advice for energy efficiency - e.g. as far as possible minimise your use of heating and eliminate draughts?


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## Carpenter (13 Oct 2005)

Yes and no.  Because we live in homes that are for all intents and purposes air tight we have to introduce some level of background ventilation otherwise condensation is inevitable.  The warmer air gets the more water vapour it can hold and this vapour will condense on the coldest surfaces within the house- behind a wardrobe, north facing walls, windows etc.  It is a good idea to eliminate heat loss through air leakage via badly fitting doors/ windows etc but this must be offset against condensation risk.  By using permavents we can regulate (via hit/miss grilles) the level of background ventilation required.  This is also a mandatory requirement under Irish Building Regulations, in fact the Conservation of Heat Regulations and Ventilation Regulations are clearly interlinked.  The Conservation of Heat TGD recognises that increased levels of insulation and elimination of draughts must be matched by improved levels of ventilation, check out www.environ.ie.


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## ClubMan (13 Oct 2005)

Fair enough - thanks for the info/explanation. By permavents do you mean the vent covers that are usually installed at the top of the wall in the corner of rooms? Is it correct that these simply cover a hole in the wall as they do in our house - i.e. there's not supposed to be anything installed between the internal and external vent or anything like that?


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## Carpenter (13 Oct 2005)

Permavents are Permanent Ventilation openings, as described by you.  The only thing you should find behind the grille is the plastic pipe which sleeves the opening in the external wall.


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## ClubMan (13 Oct 2005)

I'm not sure that we have the pipe but rather a simple hole in the wall. I must check. Does it matter if the pipe is missing? Does it serve any purpose other than to create a cleaner ventilation opening?


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## z102 (13 Oct 2005)

Permanent venting through tiny holes in the frame is the worst that one can do against enrgy wasting . Reason : The permanent cooling down of the window frames makes them colder as they are any how and that causes additional condensation .Standard PVC frames as commonly installed here in Ireland are the weakest part of the insulation at any modern home .The legal demand for U-values for the pane as well as for the wall is higher than the (still unregulated !) U-value of a standard plastic frame . 
Condensation is caused when the surface temperature is 6 degrees Celsius lower than the air temperature . That is a physical law . 
Proper - energy saving - aeration is done for a short time , if necessary repeatedly. But thouroughly: all windows fully open as well as the doors to all rooms in need of ventilation. Reason : warm air transports more moisture than cold air .Once exchanged it has to warm up again to take the moisture from the interior (getting it out from furniture and carpets etc. ) .This warming up of the fresh air can't happen if it is blown out straight away . Cold air entering the room , blowing through and leaving it does not dry the moisture containing things but cools down the room . A physical law .
The best/most efficient  time to have a thouroughly ventilation of the house is at night before bedtime . The fresh air would be drier/colder and the house wouldn't need extra heat from the heating system to warm up the temperature very quick to comfort level , it's bedtime any how . And turn off the radiators when having the windows open . 
There are heat recovering systems available that are ventilating the rooms and recovering some of the energy contained in the stale air . But don't forget to build in a condensation trap if installing those . 
Bofarr01 did not say if it is the glass pane or the frame showing condensation. Or both . A frame can be insulated by filling those trickle-vent holes and by adding an other layer of PVC to the outside. As I have done after having the problem with condensation on badly insulating PVC window frames . I solved this problem for good . If advice is needed how to do the extra insulation of the frame ( plenty of work, but cheap ) feel free to ask .
If the double gazing pane has aluminia spacers nothing can be done about the condensation along the spacers exept to exchange the panes for better quality ones . 
If the double gazing pane has a leak than condensation can be seen between the panes . As well as oxidation of the aluminia spacer at the bottom of the pane where the condensed water goes . This oxidation is a white , frost like apearing dust on the spacer.


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## Carpenter (14 Oct 2005)

Clubman- don't worry, the plastic pipe is used for reasons of convenience/ buildability in new construction but may not have been used in older houses.

Heinbloed- nowhere was any reference made to window tricklevents, all references were to permavents located in walls.  As for you suggestion that a house be best ventilated at night- I don't aggree.  The ventilation requirements of any dwelling are dependant on the patterns of usage of the dwelling.  A house that is occupied during the day, where cooking is done etc will obviously have different requirements than a house that is occupied early morning and evening only.


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## ClubMan (14 Oct 2005)

Carpenter said:
			
		

> Clubman- don't worry, the plastic pipe is used for reasons of convenience/ buildability in new construction but may not have been used in older houses.


Thanks - the house is only 10 years old. I must check all the same when I get a chance.


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## MissRibena (14 Oct 2005)

We have a good bit of condensation on the windows in the morning in my house too.  I know that ventilation is the answer but am a bit unsure how to go about it.  To be honest, I can't see me drilling the holes for permavents in the walls.  I do keep doors closed having showers and baths and open windows at the same time to ventilate as much as possible but the main problem is at night and early morning when the house is still warm from the central heating.  

Is there anything in particular I should be doing?

Thanks
Rebecca


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## ClubMan (14 Oct 2005)

MissRibena said:
			
		

> We have a good bit of condensation on the windows in the morning in my house too. I know that ventilation is the answer but am a bit unsure how to go about it. To be honest, I can't see me drilling the holes for permavents in the walls.


Surely all rooms already have such vents? Hasn't this been a building requirement for years? For example, my mother's house is probably 50 years old and has them.


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## MissRibena (14 Oct 2005)

Nah Clubman it was build in around 1930.  There are vents under the floors in one room but the others were replaced with cement floors as part of an extension/reconstruction.

They are not as "standard" as you think either because in my last house (built in 1999) I had to get the builders back to re-do them as part of the snag and he had been building the house for his son and told me that lots of people request them not to be put in in new houses, presumbably one-off type builds.  

Rebecca


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## Cahir (14 Oct 2005)

ClubMan said:
			
		

> Surely all rooms already have such vents? Hasn't this been a building requirement for years? For example, my mother's house is probably 50 years old and has them.




My parents house was built in the late seventies and there are no vents in any of the rooms.


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## Allen (14 Oct 2005)

To go back to the original question


			
				bofarr01 said:
			
		

> What exactly causes condensation..?
> B


the answer is water vapour in the air.  Some of this comes from hot water, showers, cooking etc., but most of the night time vapour comes from your breath.  So, the simple answer to stopping condensation at night is:- to stop breathing.


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## Carpenter (14 Oct 2005)

Miss Ribena

Older houses such as yours are not as airtight as a modern build therefore permavents are not strictly required (in anycase your house was built pre Building Regulations).  Air will trickle in via badly fitting windows doors and thro' fireplace openings (when not lit).
Cahir's house was also built pre regulation (1997) although some house builders of that vintage did incorporate vents in the walls.


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## MissRibena (14 Oct 2005)

Thanks Carpenter
So is there anything I should do about it or is it ok to pass no heed?  There is double glazing in the house.

Rebecca


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## Carpenter (14 Oct 2005)

Ah you see I didn't realise you had double glazed windows- which are airtight, this would be contributing to your condensation problems- the water vapour can't escape and must condense somewhere.  Your best bet is to leave windows open very slightly when cooking, washing etc. Windows should be left slightly ajar in bedrooms at night.  I live in a 1999 built house with double glazing, cavity walls and permavents and occasionally will get condensation on the glass.  We live in a damp country so some condensation is unavoidable.


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## Thrifty (14 Oct 2005)

Hi probably should start a new thread for this but i have a double glazed back door where the seal must be affected as there's condensation/fog between the glass. Put in years ago before i bought the house - anybody know how i can get this fixed - is it possible to do myself or should i ring a double glazing company and will they just fix a seal on a door.


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## ClubMan (14 Oct 2005)

If the seal on a double glazing unit is compromised then I think that the unit needs to be replaced fully. I'm not aware of there being any way to repair these or that it would be cost effective if this is possible. But I could be wrong...


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## Leo (14 Oct 2005)

Take a look at the links on Heat Recovery Ventilation on the Sustainable Development [broken link removed]These will enable good circulation while retaining most of the heat from the expelled air. 

Has anyone here any experience installing/ using these? Looking at getting something similar for my parents' house which suffers badly from condensation. 
Leo


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## MissRibena (14 Oct 2005)

My mam had condensation between the panes on her patio door and the guy took off one pane and replaced the seal. It was a year or two ago and there is no fogging since.  It cost her about €100 but I think it was a guy doing a nixer (not that I'm condoning it or anything before anyone mounts a high horse  )

Rebecca


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## Past30Now (2 Apr 2007)

MissRibena said:


> My mam had condensation between the panes on her patio door and the guy took off one pane and replaced the seal. It was a year or two ago and there is no fogging since.  It cost her about €100 but I think it was a guy doing a nixer (not that I'm condoning it or anything before anyone mounts a high horse  )
> 
> Rebecca



All of the older windows in our house have condensation between the panes.  I don't know how old they are, but would like a relatively cheap solution.  Can the seals be replaced?

Past30


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## Kaso (22 Apr 2007)

We have a similar problem - wife and I bought a second hand house last year and a lot of the double glazed windows have condensation in them (some of them are so bad that we can't see out them at all). We thought that the only way to fix the problem was to actually get them replaced and we frankly can't afford to get them replaced. Does anyone know of anyone that cleans the inside of them, like what MissRibena mentioned earlier in the thread?


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## echo (23 Apr 2007)

Hi Kaso,
I've worked in the glass industry and to be honest you are better off just replacing them. It's a messy job cutting those double glazed units open and if it was my own house I wouldn't be satisfied unless the vacumn was industrially sealed and not just sealed up with tape out your backgarden. In all probability the unit would just break down again in the near future.
Saying that, it is not all that bad. Installing glass is not that difficult once you take care. This is especially true if you have PVC frames as they are very good to work with. The main thing is to cut out the middleman- ie the glass companies. From experience I am still shocked at the amount of profit that these places have made over the last few years. The mark up is unbelievable. I have often done jobs where the glass only costed 30 to 50 euro to produce and then the company charged 200 to 400 for its installion.
These are the steps that I would take to do your house.
1. Aim to replace them as your finance allows, ie 1 every week.
2. Measure them yourself- all on the net. better still to take it out of frame- measure perfectly then and also remeember to measure thickness!
3. shop around for quotes and ask wi.ll they give it to you for builder price.
The amount of money you will save on labour will def surprise you.
In you are a total disaster at DIY then by adding a handyman to the above steps would still save you a lot of money.


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