If the window is re-designed (not exactly the same number and type of openers), ventilation could be made worse, therefore you must check you meet the following requirements for purge ventilation:
Background Ventilation
The guidance has not changed since 2006: the following applies:
Why Check?
What you need to do
All safety glazing must be visibly marked on the glass. If the ‘visible markings’ on the safety glazing material is not clear or you have any concerns about whether the safety glazing has been installed to the correct standard, you should go back to the original window installer and seek advice. If you are not happy with their response, you should contact FENSA www.fensa.org.uk
Safety Glazing is:
The shaded areas (see Figure 1) are critical locations which require the use of safety glass. These are:
Those areas of internal and external walls that are considered ‘critical locations’ in terms of safety are:
A window within 800mm of the bottom of a bath or shower should be safety glass.
Notes from FENSA
All Replacement Windows Shall Achieve:
All Replacement Doors