Misting DG window and drilling glass

[Chris Hogg]

We have a DG PVC-framed window that's just started to mist up. Many years ago, I read that if you drill a couple of small holes through the _outer_ pane, it allows the condensation to clear, but this has to be done fairly soon after misting is first seen, otherwise salt-deposits on the inside of the glass mean it becomes permanently opacified .

Has anyone any experience of drilling small holes, say 1 - 2 mm diameter, through sheet glass, and if so, what's the general procedure. I have a Dremel, and AFAICT the glass isn't toughened (it's not a door).

[meow2222]

TC tile drill, those arrow shaped ones. I don't know where you get one with 3.2mm shank, and don't know if it would be ok with that much speed.

NT

[Harry Bloomfield]

Chris Hogg wrote on 9/3/2014 :

There are companies which specialise in doing this now.

[Chris Hogg]

Thanks. I think I know the ones you mean. I have an ordinary variable speed electric drill as well as the Dremel. But are they OK for glass? I'm sure they're OK for tiles, but tiles are much softer than glass, which is very brittle and cracks tend to 'run'. Have you actually used one for drilling glass?

[Chris Hogg]

If I was going to get someone to do it, I might as well simply get the sealed unit replaced by a glazier. Thanks anyway.

[Chris Hogg]

I've just looked up TC tile drills on Amazon, and they talk about drilling glass (mirrors), so I guess they're OK. Thanks again.

[dennis]

If you are going to mess about why not drill through the side spacers at the top or bottom and put some new silica gel into the spacers. The spacers are usually hollow and have silica gel in them to keep the insides dry.

The newer ones filled with dry argon may not have silica gel in the spacers, I couldn't see any holes on the inside of the last lot I looked at.

[Tricky Dicky]

You will need to drill the glass vertically as you will have to put a dam o f plasticine around the hole position to contain water for coolant. Having to take out the glass you might as well mend it with a new one especially w hen you factor in the possibility of cracking the glass anyway.

Richard

[RobertL]

Mirrors are not made of toughened glass. DG units are usually. I suspect it will shatter into thousands of small bits if you are not careful.

Robert

[meow2222]

of plasticine around the hole position to contain water for coolant. Havin g to take out the glass you might as well mend it with a new one especially when you factor in the possibility of cracking the glass anyway.

Not hard to spray glass outdoors.

NT

[JimK]

/Dennis@home

- show quoted text - If you are going to mess about why not drill through the side spacers at the top or bottom and put some new silica gel into the spacers. The spacers are usually hollow and have silica gel in them to keep the insides dry. /q

Mmm and have you done this?! :-)

Jim K

[Tim Watts]

Usually only if fitted "low down" - below 800mm from floor IIRC as per building regs.

Otherwise they are usually plain annealed IME and if old, they are plain annealed irrespective of height!

[dennis]

No I did the sensible thing and fitted new units. 8-)

[harryagain]

Won't help. There is dessicant in the aliminium spacers. (Note the tiny holes in the visible bit between the glass.) Once there is an air leaks in and the dessicant is expended you get the condensation. Holes just let in more air and condensation.

[Lobster]

On 03 Sep 2014, Chris Hogg grunted:

How much does this impact on the efficiency of the DG, compared with a sealed, argon-filled job? I'm thinking if it's trivial enough to make it worth choosing over a replacement unit, why don't suppliers offer this as standard? I've had misted units replaced FOC under the fitter's 10-year warranty, which implies to me they wouldn' seal them if not necessary?

[Brian Gaff]

I somehow feel this is not going to work. Condensation inside a sealed unit surely means there is a breach in the seal, and damp aircan get in. as different temperatures of the air within can hold different amounts of water, it will alway mist as you do not have the silica gel there any more to absorbit.

I have one like this from the 70s, and according to a sharp eyed person, there is a tiny crack in one corner on the outside pane. Brian

[Harry Bloomfield]

Chris Hogg formulated the question :

Sorry, I was in a rush....

What I had in mind was - I saw a video of one such company offering the service. It looks very easy to DIY the process.

[Chris Hogg]

I think the idea is that small holes drilled top and bottom through the outside pane, allow outside air to circulate slowly through the inter-pane space. In this way the air between the panes will always be at or close to the humidity of the outside air, so no condensation should occur. If the holes were made through the inner pane, the humidity would be that of the house interior, and condensation would occur when it got cold, in just the same way as occurs on the inside of a single-paned window.

I've no idea if it actually works, but I'm sufficiently interested to give it a try. If it doesn't, or if I break the pane, I've lost nothing (1) and will just get a glazier to replace the whole unit anyway. Of course, it may nullify the effect of the double glazing in terms of insulation - I'll just have to find that out as well.

(1) apart from the cost of the drill; got a 3mm one this afternoon; it may also come in handy for other things.

[meow2222]

Fancy gas fill improves insulation, so drilled units won't meet the latest BR. They still insulate well, but not quite as well.

If you drill, put the hole at the bottom on the outside. Anything else will add to your troubles. Drilling throught the seal should work iff the airpath then leads to outside - if to inside it'll mist.

Once unmisted I'd plug the hole with sand & epoxy to stop insects getting in. Or right away if you don't mind demisting being very slow.

NT

[Chris Hogg]

Found this:

Looks like what I'm thinking of, although my DIY version won't be using the fancy defogging stuff.