Cascade ventilation—Air exchange efficiency in living rooms without separate supply air

• We investigate the extended cascade ventilation principle for a certain floor plan.
• The short circuit risk is determined via CFD simulations and measurements.
• Worst case boundary conditions are investigated in terms of air exchange efficiency.
• Low air exchange efficiencies were determined if the living room has no supply air.

The cascade ventilation principle offers great potential for reducing investment and operating costs and is therefore highly attractive for implementing simple and robust (low-tech) ventilation systems for sustainable buildings. The basic idea is to design the living room as a pure overflow zone. Supply air nozzles are only installed in bedrooms. This way the supply air is used most effectively and supply air rates can be reduced while still maintaining good indoor air quality for a great number of floor plan topologies. Questions remained, if the fresh air coming from the supply air rooms mixes well enough with the living room air for certain living room geometries (e.g. opposite supply-air-room and extract-air-room doors). The results of the CFD simulations as well as the measurements do confirm a short circuit flow between the overflow openings for many of the investigated worst case boundary conditions.