ot drilling glass

Water. Plenty of it, it's not for lubricating, it's for removing heat so you don't kill your cutting tools.

If the seal is broken (moisture between the panes), the windows need to be replaced. They can't be fixed.

If it's a diamond drill, use water. The idea is to cool the drill, not lubricate it. Water isn't going to hurt the drill.

The vent hole may help at times, but there is a reason why they sealed the windows to begin with. The moist air will still condense at times and the increased moisture reduces the insulation properties.

I guess it's better than buying new windows, eh?

Drilling a vent hole seems to work fine. It lets the moisture out.

There are services that will drill little holes and refill with inert gas, but if the seal is leaky that probably won't last.

I don't know about drilling but when I was doing stained glass work, the grinder I used had diamond heads and was high speed and used water as lubricant/coolant. The biggest threat to the glass is heat. If it has a low temperature coefficent (as most window glass has), heat could cause the glass to crack. So I would say high speed Dremel, water coolant and a steady hand. Cheers

The water also keeps the temperature of the glass near the hole down. You do not want the glass to get hot in a small area. The thermal expansion could crack the glass. Don't know how much of a problem this is, but why chance it.

Dan

Have not tried it, but if you drill two holes you can flush the cavity with Argon or CO2. Both of those gases have high weights and will increase the thermal resistance. Seal the holes with Silicon Caulk.

Dan

Why not take the double glass envelope out (if possible - on a hot dry day) and drill through the seal? You could then gently pressurize the glass (basketball filler tube through the seal perhaps?) and then, using soapy water around the seals, find the leak(s) and seal them up under a slight vacuum to suck in a silicon sealant. Slight positive pressure and then seal up the remaining hole.

Or drill two holes (top and bottom - process pointed out in other responses) and vacuum out the moisture on a hot day, then seal the holes with drops of glue.

I am curious about the results as we have a couple of windows whose seals have failed and was planning on replacing them...

John

Unless you fill the window with dry air of some sort you will still get condensation on cool days. If you've ever lived in a house with single pane glass you remember even on the days when it seems dry as a bone inside but freezing outside frost will form on the glass. Condensation will continue to form inside a window on cool days unless you get the dewpoint of the air inside the glass below the necessary temp. It's not like letting your towels dry out.

Slow with water made a nice little hole, and the cheap core drill wasn't worn down too badly. Well, it might be OK for another hole or two.

It usually takes some days, sometimes a week, for the condensation to work its way out.

The Renewal by Anderson salescreep wanted $22K to replace the windows. He said that included a 20% discount but, by state law, we had to sign within 24 hours to get the discount. I washed and drilled the windows in about 2 hours.

drill two holes, one the bottom one at the top

if you put the bottom one outside and top one inside, it might suck in cold dry air at the bottom and when it heats up blow out the top

-Lasse

I considered that, but if the seals are leaky the gas might get out again, like the original gas did. I don't know if that would take weeks or years. Freeze spray/duster might be a good high-molecular-weight gas. Or propane, if you don't mind a mild explosion hazard.

Drilling one hole seems to work. I've done inside and outside and both were OK.

Maybe when it rains, the seals get wet and the glass cools down, so that sucks water inside.

Also, and VERY important, keeping the GLASS cool. If the grinding bit heats the glass, it starts a crack. I'd recommend trying it on a piece of scrap window glass first to develop the technique before starting in on a thermopane window. If you don't have any, you could probably get a piece of scrap from any hardware store that cuts window glass to order.

Once you have the technique down, then you can do the windows. A 1/8" diamond bit with a Dremel should work in a couple of minutes. For a core drill, it will probably be a lot larger, so might have to turn it a lot slower.

Jon

Window glass is VERY prone to cracking, it is NOT Pyrex! It doesn't take much localized heating at all to start a crack, especially where you have a big discontinuity like a hole!

Jon

I've drilled windows at home and up here in the mountains, and it seems to work fine. I prefer outside drill on an unproven theoretical basis, as long as the hole won't get rained on, but both in and out seem to work.

Some windows have a powderey (titanium dioxide?) anti-UV coating inside. If that gets wet, it can streak and that can't be fixed. So drill sooner than later.

Try it. You don't have much to lose.

Did you drill the inside pane? Seems there is usually more moisture inside the house than outside (we use a humidifer in the winter), so that might actually make the problem worse. I've got a couple leaky thermopanes here. I've thought about pulling the panes out of the frame, re-doing the seals and then filling with Argon. But, geez, sounds like a LOT of work. Maybe the drill is the right fix for the problem.

Jon

That's why I got the diamond core drills. The pointy carbide things can crack the glass, especially if you drill near a corner. Dremeling gently takes forever.

I just made a very pretty hole close into a corner, with the core drill. Slow revs with water.

If it's an insulating glass unit, there will be dessicant material inside the spacer. Normal IGUs use butyl rubber sealant between the spacer and glass to keep air and moisture our and argon in.

A few holes may get rid of the moisture for some time, but if there's a low emissivity coating inside, that may turn grey after some time.

IGUs can't be fixed properly so that they would keep their thermal properties. But I think John lives in rather warm conditions, so that is probably not an issue.

The problem is the leaky spots have been leaking for some time, and the glass is dirty at that spot. I think the only real fix is to remove all the sealant, clean the edges of the glass with solvent and then re-seal them. Even better, the scheme I cooked up was to mask the windows and then sandblast the outer 1/4" to give the sealant more of a grip before reassembling the double pane and applying the sealer. Then, once the stuff has cured, poke hypodermic needles in and fill with Argon, then glue up the needle holes. Maybe even put the needles in before the sealant cures. But, that's a lot of work.

I think any slap-dash attempts to seal the leaks will not create a long-term seal. Also, once the things have leaked for a while, there is all sorts of crud that develops on the inner surfaces of the panes, I'd want to get that clean, and that means taking the whole double-pane apart.

Jon