Double glazing for large window - what thickness of glass ?

ebc

We are getting quotes for a new window with a fixed central pane and openers at the ends. The central pane is very large at 190cm wide by 160cm high. The window is quite low to the floor so will be of toughened glass.

We have had various quotes all for a 20mm air gap between the panes.  However, some say that the glass for the panes of the central panel will need to be 6mm thick due to the size of the panel. Another has said that they will supply 4mm glass. When we looked at sample windows (in a small size) we preferred the one from the 4mm glass supplier.

Does anyone know if a window as large as this would be OK with 4mm toughened glass or should we be choosing a 6mm toughened glass supplier ?   I have walked past houses where windows seem to bow inwards (so you see odd reflections in them) and am worried we might possibly end up with that effect.

Any advice gratefully received – thank you

NSG666

ebc said:

We are getting quotes for a new window with a fixed central pane and openers at the ends. The central pane is very large at 190cm wide by 160cm high. The window is quite low to the floor so will be of toughened glass.

We have had various quotes all for a 20mm air gap between the panes.  However, some say that the glass for the panes of the central panel will need to be 6mm thick due to the size of the panel. Another has said that they will supply 4mm glass. When we looked at sample windows (in a small size) we preferred the one from the 4mm glass supplier.

Does anyone know if a window as large as this would be OK with 4mm toughened glass or should we be choosing a 6mm toughened glass supplier ?   I have walked past houses where windows seem to bow inwards (so you see odd reflections in them) and am worried we might possibly end up with that effect.

Any advice gratefully received – thank you

I've just replaced the glazing units in my patio doors The ones replaced and the replacements use 4mm glass but your's is c. double the size. Having replaced a different couple or 6mm glass units I think I'd go for 6mm glass if I were you as they are much more rigid.

Unless you are having a pattererned glass then I'd have though that any of the companies that you have spoken with would be able to have the units made with either 4mm or 6mm glass.

greenface2

Its over 3.0m sq . It would be illegal to put in 4mm glass . consider splitting the middle one into 2 units . each approx. 930 x 1600 . would only need 4mm toughened . would be easier to fit . wouldn't flex in high winds . would be cheaper than one big 6mm unit , cheaper to change in case of problems . weight would be close to 100kg in 6/16/6 rather than 2 x 4/20/4 @ 30kgs each . 

ebc

greenface2 said:

Its over 3.0m sq . It would be illegal to put in 4mm glass . consider splitting the middle one into 2 units . each approx. 930 x 1600 . would only need 4mm toughened . would be easier to fit . wouldn't flex in high winds . would be cheaper than one big 6mm unit , cheaper to change in case of problems . weight would be close to 100kg in 6/16/6 rather than 2 x 4/20/4 @ 30kgs each . 

Thanks for the suggestion - can you point us to any document or website that advises on glass thickness for different window sizes ? (I can only find Building Regs for safety glass depending on height/position of window etc - doesn't seem to mention glass thickness relating to window size). It would be nice to know if there are any rules on this, or recommendations from any official body. Thanks.

greenface2

I will see what I can find later . But have a nose yourself . The G&G spec for toughened is B/S6206 or en1206 (I think) have a look at pilkingtons or saint gobain website , The size of 2.5m2 from memory is the point where it should go to 6mm , Unsure if that's exact size. Also at a height of more than 9 meters needs 10mm toughened and outer pane to be laminated (new builds differ again) . I do know a 6/16/6 unit toughened is triple the price of a 4/20/4 unit toughened . Yesterday I overpriced a frame upstairs where the glass was 2800 x 1100 . I didn't want to be shifting 100kg of glass upstairs with the risks involved for the customer to have an unobstructive view of their wheelie bins and dog . Split it up . If not for the price but for the fitter . HAha