Fixing blown sealed unit in situ - no, really..

[RandomGrinch]

There's nothing wrong with a 'pioneering' spirit, but there are two issues that you don't seem to be addressing.
For the unit to blow, the seal must be compromised in some way to allow moisture in, and if condensation is visible inside the unit, the desiccant within the spacer bars will be saturated.
You may be able to pass dry air through the unit, or fill it with an inert gas, but you are unlikely to dry out any of the desiccant.
And without attention to the seal, moisture ingress is still likely.
Without sorting these issues, any 'fix' is likely to be very temporary.

 

[Iwilldoit]

There's nothing wrong with a 'pioneering' spirit, but there are two issues that you don't seem to be addressing.
For the unit to blow, the seal must be compromised in some way to allow moisture in, and if condensation is visible inside the unit, the desiccant within the spacer bars will be saturated.
You may be able to pass dry air through the unit, or fill it with an inert gas, but you are unlikely to dry out any of the desiccant.
And without attention to the seal, moisture ingress is still likely.
Without sorting these issues, any 'fix' is likely to be very temporary.

Yep like I said - it may work but expect to add it to the rest of your yearly house maintenance jobs.
Something that I would not mind doing if the alternative was an expensive replacement that may well fail again.
On the desiccant question, is it a case that they are impossible to dry out or do you just think it wont work. What about on a hot day with a pump attached all day - surly that will dry it out.
I agree unless you can see an obvious place where the seal has gone you will have to try somehow to seal the lot.
And the argon - I was under the impression that the unit was manufactured and sealed in an argon atmosphere and not "pumped in"

 

[cdbe]

Plenty of people drill them to defog them - you can even get kits with vent valves. Obviously a bodge and you won't drill toughened glass but you can remove the unit and drill through the spacer and see what happens. The main thing is whether the water will leave stains when it evaporates, you'll lose some thermal efficiency but I doubt it would bankrupt you compared with the replacement cost.
I remember my dad had a go with our mahogany framed lounge window in the 80's - it made a huge difference, the only mistake was that as he drilled through the frame and glass in one go a sprinkling of fine sawdust fell into the units, but you only noticed if you looked closely!

 

[mrrusty]

I drilled a hole in a DGU once to try this bodge, and a spider took up residence inside the DGU......

 

[Iwilldoit]

I drilled a hole in a DGU once to try this bodge, and a spider took up residence inside the DGU......

 

[ronniecabers]

Sorry folks been busy then away camping then a stag do lol.
As others have said ... the unit has broken down, the dessicant is no longer active. That's your first issue
Do not drill toughened unless you want a million piece jigsaw or drill the laminate ( without proper cooling) unless you want a cracked unit. Yes you could drill one spacer bar , you'll end up with swarf in the unit and if really unlucky dessicant too! Very very unlikely this unit is a vacuum , they tend to be much thinner heritage units, this will be filled with air , probably argon at some point too. There are companies out there that will drill and run a gas through it to clean it out but...firstly if any white staining it won't get rid of it , secondly it's no longer a sealed unit, so would have absolutely no thermal properties. IF softcoat planitherm was used it will eventually degrade so you can no longer see through the unit.
6mm tough glass is not used so you can walk on it as someone mentioned , no where near thick enough... try 30mm tgh lami upwards! Reason for 6mm tough is more than likely due to risk of objects being dropped by birds etc...8.8 lami probably because it's above your head and last thing anyone wants it's glass on your head.
The drilling/defoggging method is very much considered a bodge. A rooflight like that with no thermal properties will condensate and let quite a bit of heat out compared to a sealed unit as the inside of the unit is now open to cold air

 

[Iwilldoit]

Reason for 6mm tough is more than likely due to risk of objects being dropped by birds etc...8.8 lami probably because it's above your head and last thing anyone wants it's glass on your head.

Why do velux not bother with that level of spec, is it because they are installed at an angle and not so vulnerable.
On the bird dropping thing, I was once woken up by a loud bang on the roof then later on the floor I found a very big leg of lamb bone on the driveway, so must of been a crow or something trying to fly off with it.

 

[ronniecabers]

Not sure whats in veluxs specs now but im sure its a minimum of 4mm toughened... I'm sure they use 4mm tough,/6.4 lami now, never used to , used to always just be Std 4mm window glass which is ludicrous. The sizes of most velux certainly wouldn't need 6mm or 8.8 lami . I do suspect 8.8 lami is a little over the top, but they are covering themselves in case of nany issues of breakage. I think 6.4 or 6.8 would be sufficient but that's just me

 

[creamola]

A BIG thanks to you all for your input - some really useful (and sanity reinforcing) comments here.

To be clear, if I could have found someone to do the replacement sealed unit I would. (I was going to specialists - not the usual white PVC window installers).

You are right, it is Planitherm and it has gone milky - and I also hadn't considered that desiccant in the spacers would need drying out as well.

As a direct result of all your input, I have again spoken to Surespancovers. Their takeover (of the assets in administration) of Sunsquare is now complete - and the lady there was very helpful. She said, that although she could supply a replacement sealed unit, they have discovered recently, that the original Sunsquare skylights were manufactured in multiple different ways, and it isn't possible to tell what exact sealed replacement unit is required until the frame etc is taken apart, and in a lot of cases, the sealed unit is so heavily glued in, that the surrounding frame is destroyed in the process of removal.

The next phase, is therefore for me to send all salient details and photos to Surespancovers and they will quote me for a replacement sealed unit AND replacement entire unit - as in most cases, this is turning out to be cheaper. The good news, however small, is that Surespancovers do have contractors who are experts at installing/replacing this particular product and they can connect me to them. So, this is fixable - but a lot more expensive than a can of Argon LOL!

 

[Iwilldoit]

Have a look at pyramid roof lanterns, could you replace with one of them instead

 

[creamola]

Have a look at pyramid roof lanterns, could you replace with one of them instead

Great minds think alike!

I did consider this - but rejected it for two reasons:

1. The existing skylight is in a roof with an adjacent wall (side of the house) so looking up through a pyramid lantern, I would see a big wall, whereas, the current rooflight, because it is almost flat, just gives a view of sky (only).

2. I think the reason that the architect specified the Sunsquare product (which was installed as part of a refurbishment) is because it is installed on Sunsquare's heavily insulated upstand, which we would kind of lose with a Pyramid UNLESS the Pyramid sat on the existing upstand.