Start with the acoustic report
A noise condition normally points to an acoustic report that sets a sound insulation figure for the windows, often as Rw + Ctr for each facade, and sometimes minimum values across a range of frequencies. It may also set a figure for the trickle vents, because a standard vent can let in more noise than the glass keeps out.
We read the report and the condition before pricing and build the spec to match: usually acoustic laminated glass, often in an unequal-thickness unit, with acoustic trickle vents where they are needed.
Glass figures and whole-window figures
Glass manufacturers publish figures for the glass on its own. The condition is usually about the whole window, frame included, tested to BS EN ISO 10140. We check the glass build-up fits the frame system and ask the system supplier for test data on the complete window, so your acoustic consultant has what they need to discharge the condition.
Where the figure is tight, we tell you early and explain the options, rather than finding out when the council tests the finished flats.