I have just drilled a tiny hole in a misty double glazed unit. It leaks like a seive! I'm now using a pump from a fish tank to pump air through some Calcium Chloride drying agent and into the window. The mist is clearing and its only been running for about four hours. Total cost, about ten pounds. I can keep you posted!
Drill hole
- Thread starter ArtisanJake
- Start date
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I can give you the result now Failure. once a seal has gone the unit has shot it. because you now have two entry points in the perimeter seal of the unit the one you have drilled. ok you can seal that but air is still saturating the dessicant in the spacer bar from an unknown source so moister will continue to get into the sealed unit.
we totally refuse to split down sealed units for several reasons. one very time consuming. two very dangerous, while splitting the seal with a sharp knife we have had several near misses on wrists. so have banned the procedure altogether in our workshop. and finally while you are doing a cheap favour for some one unless every bit of the original seal is removed before sending the glass back through a very expensive glass washing machine, you only need a small amount of seal on the brushes and the next two hundred sealed units have smears on from the dirty brushes inside covered in sealant. so whilst it may seem the glass merchant is being unreasonable in refusing to reseal units there are several reasons as to why he is not.
At the moment, my window is clear. It's had about six hours of drying out. I agree it's not a permanent solution since the panel still leaks like a seive. I wonder, however, how long it will stay clear for and if a small pump could be made to kick in every now and again to keep it clear. It's a very small quiet pump and would cost about £3 per year to run if it kicked in every night for 3 hours. I would be amazed if anything like that amount of operation would be required. Its extremely reliable as it has only two very robust moving parts. The dessicant can be regenerated in a normal oven as well. I know it's not a conventional approach to this problem but it is very cheap to do. We're not all made of money are we?
A
awbcm
How much would it cost to replace the exiting unit with a totally new one ?
Publish the size of your exiting unit and some will be able to tell you the replacement price. And then you can make a true price comparison.
But I must admit it sounds like sledge hammer to crack a nut to me, but each to there own.
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Its a mad solution, but funny! 
in the days before sealed units, we could keep a home-made double-glazed window free of mist by having a breathing hole (near the bottom) venting to the OUTSIDE.
Outside air is (generally) cooler and holds less moisture than inside air.
I still have a couple in the frame next to my font door which are working OK
You need somthing porous but insect-proof in the hole.
No pump required.
Outside air is (generally) cooler and holds less moisture than inside air.
I still have a couple in the frame next to my font door which are working OK
You need somthing porous but insect-proof in the hole.
No pump required.
I'm curious as to how this little tiny hole would allow outside air in to the unit? I can't see how any air will circulate, and warm moist air will always be at the top
Also if cooler external air hits the internal pane, then isn't this defeating the concept?
Excuse my youth, but I don't remember the days before sealed units
Also if cooler external air hits the internal pane, then isn't this defeating the concept?
Excuse my youth, but I don't remember the days before sealed units
it doesn't circulate, it just equalises the internal pressure, as the air in the cavity gets cooler and warmer (contracts and expands).
so the internal air is for all practical purposes motionless
this small amount of movement is enough for the saturated air inside (which is causing the misting) to be pushed out. and cool dry air to be pulled in. this may take several days on an old unit, but once done it stays clear.
If you have an old house with wooden window frames you can add another pane by fixing a slim batten to the frame and butting the glass against it and retaining it with quarter-round or similar (that's how I did the side-lights in my porch, easy because it's in the same profile as the door-frame). In this case the breathing hole slants down and out, and you stuff a scrap of fibreglass in the hole to keep out dust and insects. The batten covers this hole and only needs a pinhole to breathe. Due to the extra weight I have only done it in fixed panes.
A mistake some less clever people used to make was to think "the inside of the house is warm and dry so I'll ventilate the space to the inside"
That always fails because the temperature of the air in the cavity is always midway between inside and outside temperature, so the "indoors" air condenses on the cold outer pane.
so the internal air is for all practical purposes motionless
this small amount of movement is enough for the saturated air inside (which is causing the misting) to be pushed out. and cool dry air to be pulled in. this may take several days on an old unit, but once done it stays clear.
If you have an old house with wooden window frames you can add another pane by fixing a slim batten to the frame and butting the glass against it and retaining it with quarter-round or similar (that's how I did the side-lights in my porch, easy because it's in the same profile as the door-frame). In this case the breathing hole slants down and out, and you stuff a scrap of fibreglass in the hole to keep out dust and insects. The batten covers this hole and only needs a pinhole to breathe. Due to the extra weight I have only done it in fixed panes.
A mistake some less clever people used to make was to think "the inside of the house is warm and dry so I'll ventilate the space to the inside"
That always fails because the temperature of the air in the cavity is always midway between inside and outside temperature, so the "indoors" air condenses on the cold outer pane.
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