T'is The Season For Noticing Failed Window Seals

Failed window seals: A common cause of foggy glass which shows up more often when there is an inside/outside temperature differential.

Failed window seals: A common cause of foggy glass: One of the most common window and door issues that comes up during a home inspection is fogged glass, more commonly known as a broken seal. Interestingly enough, identifying failed seals on insulated glass is something that is specifically excluded by home inspection standards of practice. Just in case you don't know what I'm talking about, check out the photo below. Two of these four window panes have badly fogged glass.

When an insulated glass seal fails, there are three things you might see when looking through the glass: nothing different at all, condensation or dirty/hazy glass. When a seal initially fails, nothing dramatic happens, and there is no visible evidence of a failed seal. A desiccant around the perimeter of the glass unit will help to prevent moisture in the air from filling the space between the two pieces of glass. This will keep the glass looking just fine, at least for a while. This is why home inspection standards of practice exclude the identification of failed seals. There is oftentimes just no way to know.

Given enough time, moist air begins to fill the space between the two formerly-sealed pieces of glass. When temperatures remain fairly constant, you won't notice this moisture in the glass. Only after there has been a fairly rapid change in temperature, either indoors or outdoors, will you see any evidence of a failed seal. This starts out as condensation between the two panes of glass. The photo below shows a nice example of a window on a home that just this fall started showing evidence of a failed seal. This window looks perfectly fine most of the time, but as the weather turns cooler a nice little band of condensate between the pieces of glass is noticeable.

This condensate is sometimes only there for a few hours in the morning, and doesn't show up again for sometime, but I'm sure it will keep coming back more and more frequently, and the amount of condensate, or fog, will only grow. After this has happened enough times, a mineral deposit gets left on the glass, making it look dirty all the time, even when there is no condensate present. The photo below shows an example of another window with some faint, annoying deposits. A few arrows have been added to the image to highlight this area.

When insect screens are present or when the glass is dirty, fogged glass like this may not be visible. That's another reason home inspection standards of practice don't require identification of failed seals. When inspecting a home with numerous panes of fogged glass, you can often tell clients that while one can identify many locations of fogged glass, you are probably not catching every one, especially if the windows aren't perfectly clean.

Once a window or door has had a failed seal for several years, the glass gets dirty enough to the point where it's completely obvious all the time, and it becomes quite bothersome to look through the fogged glass. I had a few panes of fogged glass at my house when I moved in, but that number has grown from a "few" to a "whole bunch" in the past several years. When you can't take it any more, it is prudent to have the windows repaired or replaced.

Extending Window Life Expectancy With Cleaning

Cleaning the frames occasionally with warm water and an appropriate detergent can extend the life of UPVC windows. Unplasticized polyvinyl chloride (UPVC), a rigid, chemically resistant form of PVC used for piping, window frames, and other structures.

Could the UK’s Worsening Weather Be Shortening the Real Life Expectancy of Double Glazing? When we buy double glazing there is general assumption that it is likely to last us at least a couple of decades but could the apparently worsening UK weather be shortening the real expected life of our double glazing? Since their introduction to the UK from Germany in the 1970s PVC-U Windows have been marketed on their longevity and durability, and the relatively small amount of maintenance needed. The estimated ‘typical service life’ of these windows was revised up from 25 years to 35 years according to a BRE study commissioned by the British Plastic Federation (BPF) for windows that are ‘under normal urban and non-aggressive conditions’.
 

A movement of the Jet Stream southwards, 2012 being the wettest winter since records began, and growing concern about the likelihood of more freak weather in the future are beginning to prompt worries among some home owners about the life true expectancy of even the more durable and hitherto perceived safer investments in their home such as the double glazing.
 

Part of the possible answer could be found in the German Institute for Construction with Plastics report which indicated that faults are more likely to appear in the non PVC components of a double glazed window such as the operating mechanism or the seals. If these components were subjected to and were susceptible to the ill effects of more extreme and aggressive conditions, could this affect double glazing life expectancy?
 

Experienced double glazing installation, spares and repairs specialist Dave Pearson of Swindon Based DA Windows commented: “As I understand it, apart from high rainfall and some terrible flooding in some parts of the country the weather for the this winter period from December to February has actually been nearly average and not unusually cold – but I think you’ll find that since 1998 we’ve had 6 of the wettest winters on record. Lots of rainwater always spells worry for home owners. I’d agree that PVC-U frames of windows are likely to be one of if not the most durable components and that it’s the other parts that may need attention, maintenance and perhaps replacing in some windows during their working life”.
 

Dave went on to say “We often have to replace ‘misty’ double glazed units. This happens where the seal of the glass unit is broken, the desiccant in the space bar becomes saturated and the moisture then starts to collect in the gap between the panes. Expansion and contraction over time in response to the effect of the elements is likely to be a cause of this in some cases. Natural wear and tear of the other window elements such as friction stays, handles etc. can also result in the need for replacement parts and repairs.”
 

Dave also had some pointers for people keen to make their PVC-U windows last as long as possible.
 

“Cleaning the frames occasionally with warm water and an appropriate detergent can keep the frames looking great and can remove any deposits. If you’re able to check the gaskets, hinges and hardware when you can you may be able to quickly address and potential problems. You may need to lubricate some parts of the hardware from time to time too."
 

"On the whole though it’s my experience that PVC-U windows are extremely durable and are likely to last a very long time, and they don’t all need replacement parts or extra work. I’m not convinced that the kinds of weather we’ve been having is likely to affect your window life expectancy”.

Did you know? The word window originates from the Old Norse 'vindauga', from 'vindr – wind' and 'auga – eye', i.e. "wind eye". In Norwegian Nynorsk and Icelandic the Old Norse form has survived to this day (in Icelandic only as a less used synonym to gluggi), in Swedish the word vindöga remains as a term for a hole through the roof of a hut, and in the Danish language 'vindue' and Norwegian Bokmål 'vindu', the direct link to 'eye' is lost, just like for 'window'. The Danish (but not the Bokmål) word is pronounced fairly similarly to window.

Window is first recorded in the early 13th century, and originally referred to an unglazed hole in a roof. Window replaced the Old English 'eagþyrl', which literally means 'eye-hole,' and 'eagduru' 'eye-door'. Many Germanic languages however adopted the Latin word 'fenestra' to describe a window with glass, such as standard Swedish 'fönster', or German 'Fenster'. The use of window in English is probably due to the Scandinavian influence on the English language by means of loanwords during the Viking Age. In English the word fenester was used as a parallel until the mid-18th century and fenestration is still used to describe the arrangement of windows within a façade. Also, words such as "defenestration" are in use, meaning to throw something out of a window.

From Webster's 1828 Dictionary: Window, n. [G. The vulgar pronunciation is windor, as if from the Welsh gwyntdor, wind-door.][3]