There is a horrible trend of sealing homes up tight, and then we start to notice a raft of problems developing - in the fabric of the home, and it's inhabitants. I am lucky to live in a 1930's building in London, with plenty of ventilation built it. It is certainly not the most eco rated property, but, it is healthy. It might cost a couple of pounds more to heat over the year, but, it has proven itself over time, from coal fires, to back boilers, to central heating, air flows throughout, damp does not get a chance to thrive, nor mould nor fungi nor other related issues.