So what are the health consequences? Poor ventilation makes our homes "sick". Poor ventilation causes condensation and mould which damages the walls and makes the occupants sick. High humidity levels - can trigger allergies - complicate respiratory diseases brought by mites and mildew - allow mould, mildew and mites to thrive in the moist environment So we do need good ventilation - better air quality means a healthier environment. Ways to Improve Ventilation 1. Open d