Until the 1930s, apartment blocks around the world were ventilated exclusively using natural ventilation. However, as buildings became higher, one of the dilemmas caused by natural ventilation became clear – the need to reserve large spaces for the ventilation ducts, with an individual vertical duct being required for each room!
In 1931, the Swedish housing engineer Sven Romedahl published an article in which he drew attention to the fact that as buildings were becoming increasingly higher, rooms were becoming smaller and smaller because of all the ventilation ducts. To provide a solution, he launched the so-called overflow principle for apartment blocks by which fresh air was introduced into ‘fine’ rooms and then fed into ‘poor’ rooms before being removed. In practice, this often meant that air would enter via bedrooms and living rooms and be extracted via bathrooms, toilets and kitchens. In his opinion, one and the same vertical ventilation duct could then be used for a number of apartments as long as they were located above each other. However, in order to achieve this, the buildings would have to be ventilated mechanically.
To reduce the discomfort caused by draughts in the vicinity of air intakes, Romedahl proposed a number of solutions in which the intakes were located close to radiators. Cold down-draughts next to windows could then be avoided and the supply air also slightly pre-heated.
The first apartment block to be ventilated using Romedahl’s principles was built in 1931 in Stockholm and was fitted with mechanical ventilation based on electrically-driven extract air fans. Just over 20 years later, mechanical ventilation made its real breakthrough in apartment blocks, especially in those three or more storeys high.