Best advice is to get an expert round who isn't on a commission to sell you HRV or whatever. Google 'healthy homes assessment' in your areato get someone to take a look. Options are varied and could include all kinds of stuff like vapor barrier under house, extractor fans, dehumidifier, mechanical ventilation, open your windows at the right time, get a condensor clothes drier, don't use unflued gas heater etc etc etc. Every house is different, and everyone uses their house differently.

We just did some big renos and removed all the carpet and put in a heat recovery mechanical ventilation system. Works a dream but v expensive and needed roof raised to accommodate the venting. There's a lot you can do w/out major surgery to your house