Condensation on a skylight

7 Jan 2009
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Upminster, Essex
United Kingdom
Hi - we have a skylight on our landing and when we moved in 2 years ago, we had the glass repaired - it was single glazed georgian wire, and was replaced with toughened laminated glass of the same thickness (two pieces of glass sandwiching a plastic barrier) - I'm not sure if the old skylight had condensation issues, but it was broken in two and was held together by flashband!

The skylight is fine all year round, until about now when it gets covered in condensation. All of our other windows in the house are modern double glazed units with open trickle vents.

The skylight has an aluminium frame and is mounted on a 16" high wooden kerb - I assumed the problem was (and may still be!) that there is no air getting circulated in front of the glass - so last year I put two vents into the kerb about 5" below the glass to allow the glass to breathe. This hasn't made a significant difference though. My concern is the wetness up there will eventually cause the timbers to rot?

Is there anything I can do to reduce the condensation on this skylight? Would moving to a double/triple skinned plastic unit make a difference (even though they are ugly IMO!). I was thinking about adding a secondary glazing film but I don't know how effective they really are (and also fitting it to a horizontal "window" doesn't really seem that easy!!) -

Eventually, I'd like to replace the skylight with a triple glazed glass unit, but they always seem to be £700+ and I don't have that available at the moment.

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Obviously warm moisture laden air is getting up to touch the glass, which being single glazed is as cold from the temperature outside. The two solutions are - remove the moisture from air before it contacts the glass - or separate the cold/hot contact.
I can tell you know these things from how you have explained your thinking, but is it possible to explore the first option, remove the moisture from the air before it reaches the glass! Are you for instance drying washing indoors and could that be avoided, or are there extractor fans in the kitchen, bathroom and utility room? These may need replacing/cleaning if they are seven or so years old.
To find out if the plastic secondary glazing might work, build a light wooden frame to tightly fit in the squared aperture, cover it in plastic wrap (a roll end from a supermarket warehouse, begged) will be tougher and wider than domestic stuff, push it up and see if it does the job...pinenot :)
Cheers for the reply pinenot :)

We have an extractor in the kitchen, and our tumble dryer is in the garage. I think the only place which could easily contribute to the moisture is the bathroom which is just along the hallway (the door is probably 6' away from the skylight), but we do have an extractor fitted in there (which I always get my wife to put on, ruining her candlelit baths!) (Imagine this with a slight buzzing sound from the extractor fan: - I'm not ruling out that the extractor fan is not up to the job, but it's only two years old and hasn't exactly deteriorated. But I think it's general moisture from the air / breathing / central heating).

Another thing I got was a small dehumidifier unit - absolute piece of cr@p! It's a small plastic box full of silica gel which I have nailed to the kerb which you plug in every few days to turn on an internal heater to dry out the silica. It does suck up some moisture, but hardly noticeable. And one of them fell apart midair last year, and I'm still finding little silica balls in the carpet even now!

Where should the plastic sheeting sit? Above or below the vents?
Below the vents which I would close first either by taping or some other way, also try to seal between frame and vertical ingos. One way to test your extractor fans is hold a piece of A4 paper up to the grills, if you can pull it away whilst very gently holding it with reverse curve to the paper, horizontaly as it were, then you have a problem. If on the other hand it sticks to the grill like it's glued, then your fans OK...pinenot :)
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Yes returns from ceiling to unit, we call these ingoes. Fan may not be best but it's obviously working...pinenot :)

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