200 BC Fire-heated floors and smoky supply air
Perhaps the very first steps towards present-day ventilation can be attributed to the Greeks who were the pioneers of the so-called hypocaust system (from the Greek meaning ‘under’ and ‘burnt’). Wood-burning furnaces were sited below floor level and the resulting hot air and smoke would find its way out via smoke ducts in the floors and walls before being led out through rooftop chimneys. After the fire had burnt out, small floor hatches were opened, releasing warm air into the rooms above.
It is doubtful whether the hypocaust system can be regarded as a true ventilation system. And the warm air released into the rooms after the fires had gone out was smoky and most probably unpleasant to inhale. It was not until much later, however, that the idea of using rising hot air was used successfully for more specific ventilation purposes.
The Middle Ages Medieval churches with high ceilings
In buildings with very high ceilings, and especially in churches, there is an enormous volume of air and it would take a long time before it became polluted, perhaps longer than the time needed for a service. In this case, warm polluted air would rise up towards the roof to be released at a great height through openings in the bell or clock tower.
The Middle Ages Poisonous air in coal mines removed by using fires
In deep mines, the air was often almost stagnant, resulting in an exceedingly polluted and, occasionally, poisonous atmosphere. In order to introduce a clean supply, the air in the mine was heated by lighting fires. The resulting rising air was then removed via ducts and chimneys, and fresh air subsequently drawn in via other remote ducts. The capacity of such systems was limited and they required enormous amounts of fuel.
The High Middle Ages Chimney cowls helped create better draughts
Rotatable cowls on the tops of chimneys became more common. These could turn with the wind, so that the smoke outlet was always on the downwind side. The wind would also create a stronger draught up through the chimney and help discharge the smoke more effectively.
The 1500s Ventilation towers for warm rising air
A number of non-ecclesiastical public meeting rooms were equipped with towers or heightened chimneys to increase the stack effect. These ventilation towers increased the upward draughts and drew out the poor air from the buildings. Two early examples, both in Belgium, were the Old Civil Registry in Bruges completed in 1537 and the Town Hall in Antwerp completed in 1565.