Hi there - we are extending the rear of our bungalow then knocking through to create an open plan lounge / kitchen. The total floor area will be about 50 square meters. At the rear, kitchen end there will be a set of 3m wide bi fold doors and a small kitchen window to the side. At the front lounge end there will be a floor to ceiling 3 pane window with the inner pane tilting in as an opening. Does anyone know if the bi folds count towards the ventilation rules of 1/20th of the floor are needing to be ventilated please? Or is it purely windows?? Many thanks![/b]