Old window with two independent panes of glass

Hi,
I live in Sweden on a house boat which has an old window from around 1890. It's made up of many small sections (not sure of the technical term for this), each containing two panes of 2mm glass with a 25mm void between them. The window is fixed (not made to be opened).
I'm currently refurbishing it as the putty and paint is very old. The external panes are sealed with putty, but the internal panes are simply held in place with pins, though a few of them have been bodged and have draught excluder strips behind them! I'm wondering if I should also seal the internal panes in place, to improve the window's insulating properties. I was thinking to use glazing silicone behind the glass to seal it, and put wooden beading over the glass to hide the silicone. My worry with doing this is that I'll seal in the air between the glass, which will then steam up and perhaps get mouldy!
Is it better to seal both panes of glass or leave the internal panes unsealed to allow fresh air in between the panes?
I'm not interested in installing double glazed panes, injecting gas to create a vacuum etc, as it's not financially viable for this project.
Thanks in advance,
Rob

 

Yes, what you're describing is common with the Insulating Glass Units commonly used in windows here in the states - the seal gets compromised somewhere and then the inside panes fog. It is a factory process to evacuate the air between the panes and not a DIY job.

 

Sealing both panes will commonly lead to fogging between the glass during cold weather. I would not recommend you seal the internal panes, bit instead leave them as is and allow them to breathe.

 

@xsleeper thanks for the reply.
Do you think it would be ok to just fit wooden beading around the glass, and not use any sealant behind the glue? It doesn't look very smart as it is now, with just tacks holding the glass in place.
As the window's so old, nothing is completely straight or flat, so a little air should still be able to flow behind the glass. Do you think this is a bad idea? I'm not sure how much space is needed to allow for enough free air flow to prevent fogging. I guess it depends on the external elements too.

 

I meant to write "sealant behind the GLASS", not "GLUE"

 

Hard to know what's a good choice aesthetically since we can't see it but your plan seems ok. That said, this sounds like a lot of work, would it not be easier to replace the window?

 

Before double pane glass, there used to be a lot of windows that had an interior storm panel that just fit loosely on the inside, with thumb turns... nothing for weatherstripping. One window in particular I am thinking of had vent holes between the 2 pieces of glass. If anyone tried to caulk the outside perimeter of the sash, it would plug those vent holes and the window would fog up in the winter. That's what I'm thinking of.

But now that I think about it, if you can prevent your warm interior air from getting between the glass in the first place, it would likely be an improvement. But if you use sealant (silicone) behind the glass, it will make it impossible to remove without breaking the glass. If you caulk on the interior side of the interior glass with a very fine bead, you could always cut it with a knife to get the glass out. And you would need to have both sides of the glass as clean as you can get them before you seal it up.

A wooden bead in front of the glass might be okay. Nailing those small beads on is tricky unless you have a 23 gauge pin gun.