In the previous articles you could read about ventilation rates and evolvement of ventilation system throughout the centuries, and here you can read more about ventilation in domestic buildings with focus on system in Sweden.
Ventilation and heating are interconnected as fires in ovens and fireplaces create negative pressure in a building and upward air stream in the flue – the stack effect. The air in a building can be replaced by infiltration through windows / doors and cracks in walls thus creating another ventilation source, even the draught.
In 1700s and 1800s the windows were improved with inner casements in winter with one movable and open able pane in upper part of a window. At the end of 1900s the buildings were equipped with hydronic radiator system in rooms and especially in bathrooms located in cores of wide buildings using stack effect. The principle was to have two separate ducts for intake and exhaust in bathrooms. The exhaust pipe in ceiling works due to the stack effect and the intake pipe is located near the floor leading to the ground floor on the shady side of a building. The kitchens and living rooms have their own inlets and exhausts in the external walls next to the windows through the flap vent or later disco valve or intakes under window sills.
The stack effect – warm air is lighter than cold air the exhaust air raises thermally up and out of the building. The greater the difference in temperature between indoor and outdoor air, the more effective the stack effect. Therefore the stack effect always works better in winter due to the large temperature difference and in summer the inlets are usually on shade place on the ground floor where the temperature is cooler and the exhaust flue is fixed with metal plate on the roof which heats it up and all this also helps with stack effect. Also the flues have to be installed in raising angles (slopes) or vertical in order to work.
After 1930s the fan ventilation were introduced with overflow method, i.e. air intakes in right way from bedrooms and living rooms to the bathroom and kitchen. And later this system was connected to axial fans and disc valves with low pressure but with the outdoor air still taken in through slotted vents beneath windows. In 1970s the supply and exhaust ventilation system with heat recovery was used even due to the problems with maintenance and high operation costs. So in 1980s there was a return to the exhaust system only with combination of heat pump for recovery and heating up of hot water and in-take radiators where the air was filtered and preheated. In 1990s the exhaust and supply air system are again used.
Source: Ventilation in historic buildings by National Property Board Sweden, www.sfv.se