Laminated glass behind victorian glass

[Mrxman]

Hi There

I've been refurbishing our old victorian door and want to add a sheet of laminate glass behind exiting glass for safety and hopefully a little extra insulation.
I have a concern about whether moisture could get in between the two sheets though.

Would anyone be able to advice me about the best approach and whether moisture could be a problem?

Many thanks

 

[JohnD]

easy peasy when you know

i have done a few similar

the trick with secondary glazing is that it must be sealed from the room air (which is warm and humid) but can vent to the outside (which is generally colder and therefore contains less water vapour*) sufficiently to equalise pressure in the cavity.

You only need a small hole. Say, 4mm in the frame. I would dribble wood preserver through it to reduce the risk of rot, and plug it with a wisp of fibreglass to keep out most dust and insects, and position and angle it so rain is unlikely to run in.

Amateurs frequently insist on ventilating into the room, on the ground that it is warm and dry, but they are mistaking *relative humidity with the amount of moisture in the air. Cold outdoor air holds less than warm indoor air.

A bucket of hot, dry air in the Sahara holds more water that a bucket of cold, damp air in Manchester.

I think I might put the laminated pane on the outside to protect your leaded lights from the weather, and so that a burglar will hit it before he reaches your old glass. If you install it with adhesive glazing tape it will be very resistant to attempts to remove it, even if broken

the pocket of still air will provide good insulation. A gap of about 18mm is ideal. Ventilating the gap with a pinhole will not prevent the insulation. The thicker laminate will also noticeably reduce noise.

 

[Mrxman]

easy peasy when you know

i have done a few similar

the trick with secondary glazing is that it must be sealed from the room air (which is warm and humid) but can vent to the outside (which is generally colder and therefore contains less water vapour*) sufficiently to equalise pressure in the cavity.

You only need a small hole. Say, 4mm in the frame. I would dribble wood preserver through it to reduce the risk of rot, and plug it with a wisp of fibreglass to keep out most dust and insects, and position and angle it so rain is unlikely to run in.

Amateurs frequently insist on ventilating into the room, on the ground that it is warm and dry, but they are mistaking *relative humidity with the amount of moisture in the air. Cold outdoor air holds less than warm indoor air.

A bucket of hot, dry air in the Sahara holds more water that a bucket of cold, damp air in Manchester.

I think I might put the laminated pane on the outside to protect your leaded lights from the weather, and so that a burglar will hit it before he reaches your old glass. If you install it with adhesive glazing tape it will be very resistant to attempts to remove it, even if broken

the pocket of still air will provide good insulation. A gap of about 18mm is ideal. Ventilating the gap with a pinhole will not prevent the insulation. The thicker laminate will also noticeably reduce noise.

Thanks John, much appreciated.
So a 4mm hole drilled into the wood glass panel at an angle from outside for ventilation is that correct?

Makes sense to put the laminated glass on outside. Come to think of it, I've seen others do that as well.

Our door is only 4.5 cm thick unfortunately so don't think we'll get much of a gap between the two glass sheets.

 

[JohnD]

So a 4mm hole drilled into the wood glass panel at an angle from outside for ventilation is that correct?

one end of the hole open to the cavity, one end open to the outside air. And sloped so the outside is lower then the inside

you can use a smaller hole, but it is more likely to get blocked. it only needs to equalise the pressure when the air in the gap expands and contracts with temperature changes.

 

[Mrxman]

one end of the hole open to the cavity, one end open to the outside air. And sloped so the outside is lower then the inside

you can use a smaller hole, but it is more likely to get blocked. it only needs to equalise the pressure when the air in the gap expands and contracts with temperature changes.

Awesome thanks