I have a house from early 1900s and had a DPC course injected and renewed plaster throughout house (back to brick). Still got damp patches in certain places throughout house and on bedroom window it would be full of condensation on a morning. Everything external was sound. I was told that mould only grows on fresh water so it wasn't rising damp that was causing it, but the fact that every day we give out huge amounts of water through breathing, washing, showers, drying clothes inside, cooking etc. All the hot air an water in the air is then attracted straight to all the coldest parts of the house ie the windows, certain patches of walls etc.
I installed a positive input fan in the loft with a grill in ceiling at the top of the stairs. This blows air constantly into the house from loft space (I have
tile vents in roof too) and since then it has cleared all the damp patches and mould on walls and I no longer have a strange musty type smell in house after being at work all day. The bedroom window at the worst time during winter barely got an inch of condensation.
I understand that this may not cure all problems and if there is some other underlining problem may not fix it but in my case it did fix it. You maybe worth researching positive input fans on Internet.
As for noise levels from fan there are different speed settings and we have ours turned down to about 1/3 power. The only way of knowing it is on is to put hand up to vent an feel for blowing air.
Hope this bit of info helps.
I'm not a genius just full of random facts that are of no use
