Continuous Extraction Ventilation

[FletchingStraight]

We're doing up an older property & want to improve the humidity levels to reduce the amount of mould. We've replaced all the old single pane windows which has helped massively but as it's limestone it holds a level of moisture & then we get mould on the stone mullions inside the house.

Anyone have any knowledge about a continuous extraction ventilation system? There's no way we could do a heat recovery system as we'd never get a decent level of airtightness to make it worthwhile. Thought this could be our solution...open to other ideas that may be out there too

Not directly, but a friend had a forced ventilation system put in a Victorian house. Previously he'd struggled with damp for years, trying one thing and then another. After he had the system put in, the house dried out and that was the end of the problem- he says he wishes he'd had it done years before.
Our house is 1920s, clearing out underfloor vents and putting windows in with trickle vents sorted the ventilation for us- though we do open some small windows in the older, lime plastered, rooms for a short while every day as well.

That's really interesting to hear about your friend, precisely what I wanted to know.
Although not some you would be able to answer but I would like to know more about any maintenance, cleaning of ducts/filters, servicing, noise etc.

We open windows daily & when it's dry & not too cold they are open for the majority of the day. Otherwise it's for an hour or two. The issue is the stone mullions. They're cold & will always be a condensation point in the house, not something we can remove either! So we have to manage humidity.

We have a constant running bathroom fan (at a low speed which boosts when the light is on or humidy is high)
We were told that the theory is all houses leak so you draw air out of damp areas like bathrooms and kitchen and dryer, fresh air seeps in through trickle vents, under doors etc.
We don't have any damp issues but then I don't think we did before!