New French Doors Fog Up

Smiegel

Hi,

Just spent about 2 grand getting french doors put into the kitchen. The problem is that every morning they are fogged even though every other window in the house is clear. Have the doors been put in incorrectly?

P.S The fog is on the outside of the doors.

Cheers

10-10-20

Please just confirm that the fog is external and not between the glass sheets?

oleras

I have this also on a conservatory put up 3 years ago, the condensation is on the outside of the glass.

SoldOut

Do you know what type of glass was used in these units? Was it some type of Low E, maybe K glass? If so its basically caused by the fact that the Low E Glass is doing its job so well and reflecting heat back into the room.

This is an explanation by Pilkingtons :

Condensation on external glass surfaces

External condensation (dew) can occasionally occur on highly insulating glass units in temperate climates. Such occurrences will only happen on cloud-free nights when there is little or no wind and usually when a warm front follows a dry spell.

The combination of several factors, namely external air temperature, localised microclimate and the thermal transmittance of the glazing itself may all contribute to the formation of external condensation. As a consequence of variable temperatures and localised conditions, it is possible to experience a situation whereby both clear and ‘misted’ windows exist at the same time in the same development.

This phenomenon is influenced by the thermal insulation of the glazing. Single glazing offers poor thermal insulation therefore heat escaping from inside a room readily passes through the glass to the outside environment. Consequently, the external surface temperature of single glazing is generally higher than the‘ dew-point’ temperature of the outside air, thus prohibiting the formation of condensation on that surface.

With conventional double glazing the thermal insulation is improved, but sufficient heat still escapes through the glass so as to warm the external surface of the outermost glass, thereby precluding the formation of condensation in most circumstances.

In common with other low emissivity glasses, Pilkington K Glass reflects heat back into the room and as such the quantity of heat passing through the glazing is reduced. Consequently the external pane of low emissivity double glazing is not warmed by escaping heat (which instead is retained within the room) and therefore presents a colder surface to the outside environment.

In such cases, and in situations where the external glass surface temperature is lower than the ‘dew-point’ of the air, (and when weather conditions are comparable to those mentioned previously) condensation can form on the external glass surface.

However, the combination of these contributing factors is largely unpredictable and therefore it is not possible to quantify the number of occasions when external condensation will occur.

Instances of external condensation are relatively rare and in all cases it will be a transient effect. Upon any one of the climatalogical variables changing, the condensation on the glazing will usually dissipate within a short period of time in much the same way as morning dew.

Smiegel

Thanks for that, very enlightening

Ill just tell my wife that when she tries to look out the window in the morning!

Reyman

Good post - Soldout! I also have outside condensation on my triple glazed low E windows and I was wondering why!

Now I'm clear - thanks! (pun)

Papad

Yes, very good post Soldout. I was thinking about this phenomenon in bed last night.
(I know, Woe is my Life).

mapuche

SoldOut wrote: »

Do you know what type of glass was used in these units? Was it some type of Low E, maybe K glass? If so its basically caused by the fact that the Low E Glass is doing its job so well and reflecting heat back into the room.

That definitely sounds plausible and what is described by Pilkington roughly fits my situation. Every other window in the house was fitted about 10 years ago so I guess technology has moved on. Bit irksome though that the other windows are leaking relatively more heat than this one.

tks for the info

builditwell

+100 for soldout. Thiss solves a multitude of problems.!!

B