The building regulations now state that areas known as 'critical locations' should be glazed in safety glass.
The image above shows the areas that should be safety glass in light blue.
The general rule is that if it's in a door it should be safety glass.
Safety glass can be laminated or Toughened. Toughened being the cheaper and more popular of the two.
Laminated glass, however, must be used in public buildings. Toughened is not allowed.
For more details on the current building regulations please contact your local authority.
New Build or New Extension or New Windows/Doors Etc.
It must be noted that latest Building Regulations(2012) do not take into account U-Values only.
On untested windows a minimum of 4-16-4 Lowe sealed unit, Argon filled with warm edge spacer bar is required.
You could assume that minimum triple glazed unit would be 4-10-4-10-4(32mm) Lowe sealed unit, Argon filled with warm edge spacer bar is required but there is nothing that is been written down and can-not be taken as correct. Your Building Inspector will advise.
On doors if glass area is less than 50% then the above does have to be adhere to but if more that it does.
Windows/Doors many manufacturers have had there products tested to insulation value and give the requirements of glass required.
Also the designers of a property or extension may trade of insulation from walls to windows or roof to floor etc etc. So they would give details of what is required. Replacing glass only in a window/door do only need to come up to the standard what is already there.
The above information as been unraveled from various publication that do contradict itself. This is our interpretation but Bromyard Glass Ltd accepts no responsibility that they are correct.