>Second, for me the most important feature is that the house should be a healthy space. Few houses have continuous filtered air ventilation systems, and it make

>Second, for me the most important feature is that the house should be a healthy space. Few houses have continuous filtered air ventilation systems, and it makes a huge difference to avoid mould, CO and VOCs. It doesn't have to be something centralized and superfancy. You can have them per room. +1 for that, it is one of the most overlooked parts in modern building, in practice you cannot have a house Class C or higher (B ot A, let alone A+) without a valid air ventilation/renew system. Particularly if you (and wife/partner/family) work full-time. Once upon a time (and in tradditional houses that were thermal inefficient but much more permeable to vapour and had this or that form of natural ventilation) the wife (that stayed at home) would open all windows in the morning, undo the beds and put the linen to the air, once a week or so also pput matresses on windows sills, etc. Nowadays the house (which is airtight in order to be energy efficient) is kept with all foors and windows closed at all times and this creates an amount of humidity (and conversely dew/mould) that is NOT healthy.