HELP, my new windows have condensation…….OUTSIDE!


A user wrote to us requesting help because he has a problem with some new windows but everyone is telling him, “they’re fine”…….Nobody in the industry seems to be willing to assist him, he feels cheated, really disappointed with his new windows and he doesn’t know where or to whom ne should turn to for help.

Now that’s not good for him, for the company he used to install the windows nor the industry in general, but who would you turn to if your new windows had external condensation and everyone said they were fine?

Every autumn this subject raises its head and is likely to become more prevalent with the increased use of triple glazing or energy efficient glazing. You need to understand how it is formed and the issues surrounding it, so that you minimise the risks or avoid the surprise should it occur!

The GGF Glass and Glazing Federation have a free consumer leaflet to download here

The problem.
You get up in the morning and on the external face of the glass is condensation or ice, just like the dew or ice that forms on a car over night. Just as with cars, this external window condensation doesn’t occur the whole year just when its cold. So is the new window faulty, is it a sign of excellence or just physics and unavoidable?

The physics first.
The car analogy is most apt. If the atmospherics are right when it’s left outside, then cold air condenses onto the coldest surfaces, often the windscreen first (because it is thinner than the roof and therefore colder) then the other surfaces.

Maybe the bonnet avoids it because it was still warm (or warmer) and dew unable to condense on it. Even so, a quick scrape of the windscreen or 3 minutes with the heater elements or warm air blower and the ice has vanished.
So is this a fault of the car or just an inconvienient natural occurrence?

Why is it suddenly a problem now with windows?
Well, ice has been known to form on the outside of single glazed windows but that was before we started heating our homes. Since then the glass in windows has been warmed from the heat inside the room escaping, keeping the external glass surface temperature above the dew point (preventing dew or condensation from forming). Even double glazing had some heat loss, keeping the external surface slightly warmer than the cold brickwork, hence dampness on brick walls but not the windows.

However since the introduction of energy efficient windows, gas filled units and triple glazing (to meet the governments targets to lower heat loss from homes), it seems external window condensation has returned.

The most logical theory for this is that the more energy efficient the glass is, the less heat it allows to escape through the sealed unit, so the external face is colder than it would be on a less efficient sealed unit from 10 years ago.

So do the best windows have condensation on them?
Well possibly but not definitely. You see, just as a car could be under a tree, in a breezy location or the engine still warm, so windows will act differently too. Some people close their curtains at night trapping in the warmth still further (so the outside will definitely be prone to dew forming), others leave their curtains open or they are so thin there’s no protection or heat retention (so the warmth gets to the windows).

Some people switch off their heating early evening, others keep it on all night, so you see its impossible to say for certain if you will have a problem, when it is likely to occur or how badly you’ll be affected, so much depends upon how you heat and use your home.

So how to get rid of it?
In short the industry has a problem. This is a newish problem. The fact is, the lower the u-value of windows, the cooler the external surface will be, the more likely this problem will be, yet the government is adamant that they require the industry to lower the heat loss and u-values still further! There may be one solution. Self cleaning glass or more accurately “glass with a coating to disperse water” may help remove the moisture as it forms. Pilkingtons have Pilks Activ and Saint Gobain have some info here

Before explaining the differences, you may be surprised to learn that the surface of glass is far from smooth. Whilst it is smooth to our finger tips, the surface is pitted with microscopic divots. These mini pot holes collect rain water and the dirt, that’s why window glass needs cleaning. There are surface treatments that apply a thin layer filling in these holes but because its see through, vision is unaffected. Now rain droplets have no where to cling onto, so it reduces the build up of Dew forming on the outside.

There are two types of product: hydrophilic and hygroscopic.

Hydrophilic encourages droplets to collate into larger globules, which run down the glass quicker and easier, whilst hygroscopic is like vinegar on water, it sheets, it produces a thin sheet of water instead of droplets. There is a company called Ritec who have a number of products but “Clearshield” stops dirty water sticking to glass,watch this 10 second video!

Neither will prevent the physics happening. Dew will always form on the coldest surfaces, it may however alleviate the appearance because it should help disperse the moisture and prevent the unsightly build up of condensation.

So are the windows fit for purpose?
Well probably yes, if they have sealed units and frames window energy rated as “C Rated” or better, or they have a u value of 1.6 or better, then they meet the building regulations.

However if I cannot see out of my windows surely they fail to provide the service I was looking for, see through and clear daylight? Well that’s where Trading Standards, the Advertising Standards Agency (ASA), perhaps the Energy Savings Trust (EST) and the Ombudsman Associations, The Glazing Ombudsman (TGO) or The Double Glazing & Conservatory Ombudsman Scheme (DGCOS) would step in.

Will Fensa step in to sort this out?
Probably not, it isn’t a fault if the windows are compliant with building regulations.

What about the GGF, DGCOS or an Ombudsman, will they help?
Well certainly not if the company isn’t a member, as these organisations only step in when a customers of a member company complains (that’s why you should use companies who belong to accredited organisations). However if the work has been done in accordance with building regulations, its not like the windows are faulty, they’re  just very energy efficient!

Ombudsman associations may consider if the customer should have been made aware that it “may” occur, before entering into a contract but none have yet come to light.

Hopefully companies will consider offering glass with these coatings or retro fitting Ritec’s “Clearshield” to reduce the occurrence, if not the actual build up of external condensation.

Here’s an extract from the writers letter,

I’m sick and tired of contacting FENSA who appear to have no interest what so ever. The only response I ever get back from them is a long the lines of, “The installation meets with Building Regulations and /or The works do not come within their remit”.

I’ve tried the Glass & Glazing Federation and they’re not interested because the company which did the work isn’t a GGF member, unless I’m prepared to splash out almost £1000 to have an independent survey carried out.

I’ve tried the DCGOS who haven’t even had the courtesy of giving me an acknowledgement let alone a response.

I’ve contacted the Glazing Manufacturer / Supplier, who also have not bothered responding.

My question is, where or who do I turn to as a consumer, I am expected to pay £1000’s for an installation I’m not satisfied with.

So how should the writer proceed?

Our recommendation is to use Trading Standards and an Ombudsman, they are there to ensure companies have done the right things and find solutions if they fell short of the mark. Companies however must belong to the Ombudsman, they wont decide if a company isn’t a member so check before you buy! If you chose to buy from a company who doesn’t subscribe to an ombudsman organisation (TGO or DGCOS), or a trade association like the GGF, then you will have no opportunity to get your case heard by them, in other words you’re on your own!

Otherwise its the trading standards office, or consumer direct they will have to decide if the goods are fit for purpose. They will be because they meet building regs but I have no idea how they will view (pardon no pun intended) the issue of not being able to see out of the window.

As for the double glazing companies out there thinking it wont happen to them, perhaps you should advise consumers up front that occasionally, very occasionally, external condensation can occur because really good units are now being used.

What’s your view, have you had external condensation, how was it resolved, can you offer a solution?

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