Hi,
will it work if I create a gap in the glass for ventilation on an enclosure?
Thus, for one of the side panes I use 2 pieces of glass and silicon them so that there is a 4mm gap between them.

I'm struggling to find nice vents and thought this might be an option.
N.

It will work perfectly... 4mm is more than enough... just take in consideration the size of the spidey... the ventilation is mainly there to control the humidity of the enclosure, the more ventilation, the less humidity...

Sent with Uncle Charlie's Pokie machine

What Uncle Charley said, plus:

My first enclosure build is somewhere else here on the forum. 200x250x400 (WxHxD) for pics.
2x1mm slits at the bottom and 2x 1mm slits at the top. I was surprised at how quickly the substrate dried out.

I wouldn't go bigger than 1mm for T's losing legs through the openings. Or mesh it up. T's can chew through aluminium and stainless mesh, but with only 4mm gap to get to the mesh I doubt that'd be an issue.

Something interesting regarding this.
I have one of the cages with the slits on top, Aquahadia I think.

One of the strips came loose, and I thought I would move it a bit to increase the gap for ventilation.
Made it about 4 or 5 mm.

A wile later I was playing games, when my wife came into the room.
She gave this little eek sound and froze.
Turns out my 14 or 15 cm L.parahybana squeezed through the gap and was very quietly sitting on top of its enclosure.

The gaps are 1mm again.

Something to keep in mind. .....

Sent from my GT-N7100 a long time ago and far, far away.....

You also need to take breeding into account, if you let the mother hatch the slings out in the enclosures.
Also your feeders, they will climb out with out an issue.

Thank you all for the good inputs.
I will go for multiple 1mm gaps then, I don't intend breeding for now and these will be for my larger arboreal T's (who desperately need bigger homes).
Now I can order my glass and get this going.