Hello, and thank you for your help in advance!
Scenario
I'm ground/1st floor in a c. 8 floor block. The block has ventilation shafts with fans at the top (roof). So, each vent in the flats is simply a vent / no fan.
I'm mid-refurb of the whole place. Unaware of any issues, I installed an in-line fan to service an existing bathroom and newly created en suite. This was then attached to existing ducting. External ventilation is not possible.
Issue
The freeholder (council) noticed this during an inspection and objected. Says I must remove them, as my fans will blow air in to neighbouring properties. Other than the hassle and wasted cost, my main concern is that, given the added en suite (and both rooms have powerful showers) there just isn't any chance of the incumbent 1970s system giving me an effective flow rate.
I objected and they sent a "ventilation expert". By his own admission he was no expert (ex IT contractor). He suggested I just pay for "no return vents" for my neighbours if they did indeed experience backdraft. I'd be happy with this, if it worked. My fear is, even if the council accept his report when it is sent, it won't a) because from google it seems these just stop air flow full stop, meaning neighbours don't get ventilation when I do and b) air will follow the path of least resistance and this may mean the vents never open at all, backdraft or not.
Solutions?
• Do you have any thoughts at all as to how to solve my dilemma?
• If I just finish fan installation, turn them on, and go into neighbouring flats to "feel" if their air is still going in rather than out is that a sufficient test of long-term issues or might differing conditions cause a backdraft down the line?
• Is there some kind of vent I can pay for for the neighbours (without invasive installation) that will resolve the possible problem and keep their ventilation functional?
• Am I right to worry the ventilation without an active fan is likely to be insufficient?
Thank you!!