Condensation mitigation

[rubybleu]

We live in a basement Victorian converted flat and despite ventilating (windows) as much as possible and running a dehumidifier, we can't keep on top of the condensation.

I've been looking into positive input ventilation systems like the Nuaire Flatmaster but it's fairly expensive. Has anyone installed one or any other mechanical ventilation system that has settled down humidity levels in their house/flat?

There was one installed in a flat that we moved into 7 years ago - not sure of the brand, and it has been there for three years by then so I'm sure the technology has moved on in ten years! It was pretty noisy, it had two 'modes' and both were noticeable. And it didn't really help with condensation - the room it was in was actually the worst in the flat.

I don't think I've been very helpful as I'm sure modern systems are more effective!

We are just about to move into a house that is only 9 years old and effectively insulated and ventilated as after 15 years of scraping mould and peeling paint off the walls of period properties I am done!

The problem may be cold surfaces rather than just humidity. If the dehumidifier is taking water out and the humidity is low, maybe you should consider insulation.
A fan will be cheaper to run but a dehumidifier should be effective.

I have a first floor maisonette. Always had problems with condensation and mould. You have my sympathy as it is terrible to live with, especially now the weather is getting colder. Last year I had Envirovent Loft Unit and two cyclone extractor fans fitted and have had no problems since. Flat feels warmer and air fresher. No noise. The extractors detect moisture and turn on when required. You can just forget it is there. It was expensive but worth it, I wish I had done it ages ago. The guy fitted it all in 6 hours, was really tidy. I did need to get permission from my freeholder first but was straight forward.
They will come and give you a free survey, which I found helpful to find out exactly what was causing it and where problem areas are. I didn't feel pressured by them to go further. They do systems for flats with no loft spaces too.

it's a basement flat so very likely moisture is penetrating the floor and walls.

Lots of ventilation will suck out the moist air and replace it with dry, but you will mostly lose some heat as well.

There us a good chance that the amount of water is increased by plumbing faults and leaks, and old cracked and broken drains. So try to investigate such defects as fixing them may make a big improvement.

The modern approach to basements is to accept that water will penetrate the envelope, and to construct inner walls and floors, allowing water to penetrate and to run under the inner floor to a sump so it can be pumped away. Some building work and probably excavation will be required, implying costs.

So I'd urge you to start by investigating the sources of water. It is normal for a Victorian property to have leaking pipes and drains, both inside and out.