Rockwool in intermediate floor joists and next to solid brick wall will this stop air flow and promote mould

[buildlondon363]

Hi,
I am renovating a Victorian house with solid brick walls and the floor between 2 habitable flats one being a basement. I want to insulate to reduce noise and make warmer for basement flat. I have 100mm rockwool and not sure if u should apply to the bay right at the edge as I don’t want it to trap moisture or stop airflow. Maybe I’m overthinking. Read a lot about a vapour barrier too but not sure if this is necessary. Surely if basement flat and upstairs is ventilated then there shouldn’t get a lot of moisture in the intermediate floor anyway? Concerned about putting insulation in the gap at bay. Pictures below.
Many thanks in advance.
They were rented before and no flooring so looks like drinks have been spilled in past down gaps. The here was wood worm slightly too but I think that was from condensation also. Going to add vents to make both flats to allow more airflow.

 

[Cubist]

I would think that the net gain, in terms of enhanced heat retention and noise reduction, from that very small area would be negligible overall. I wouldn't bother, particularly as some of those stains may be due to rainwater penetration resulting from someone leaving those sashes open. You're already treating the timbers for the wood-munchers so I'll so no more.

 

[paulc]

I am renovating a Victorian house with solid brick walls and the floor between 2 habitable flats one being a basement. I want to insulate to reduce noise and make warmer for basement flat. I have 100mm rockwool and not sure if u should apply to the bay right at the edge as I don’t want it to trap moisture or stop airflow.

I've stuffed 100mm of fibreglass loft insulation in the void between the ceiling of my lounge and the floor of the bedroom above. It has made little discernible difference to noise transmission. Next door neighbour lined the walls & roof of his garage with a sound blocking insulation when he converted into a recording studio and practice room. Didn't reduce the noise that I could hear from outside by much.

Reducing noise transmission is a complex subject and relies on mass, inserting isomeric barriers between joists & flooring, and attention to finishing details. High density insulation batts under the floorboards will reduce some of the noise. Rubber strips laid across the top of every joist before fixing the boards down will cut impact noise. To do a proper job would require the services of an expert in the field.

 

[buildlondon363]

Thank you both for your replies, much appreciated