The replacement of windows and doors require compliance with building regulations:
Fire escape: Provision should be made to ensure that means of escape in case of fire is maintained and made no worse as a result of a replacement glazing installation. All first floor windows in dwellings should ideally have opening lights large enough to allow you to escape through them if you were trapped in the room by a fire. This also applies to rooms in bungalows which open into a hall (unless the hall itself has an external door through which you could escape).
Safety glass: Safety glass should be installed in what is termed as 'critical glazing areas' i.e in doors or a window which is within 300mm of a door and below 1500mm from floor height. Any window which is within 800mm of the internal floor.
Trickle ventilation: Any new built house should have trickle ventilation as should windows or doors which are replacing existing which have trickle ventilation.