Dimensionless design approach, applicability and energy performance of stack-based hybrid ventilation for multi-story buildings

The active building ventilation systems, which remove excess heat, humidity and contaminants from indoor environment, could be large energy consumers. To provide desired ventilation flow rates for all of the floors of a multi-story building and to reduce the resulting energy consumption, a stack-based hybrid ventilation scheme is proposed. This hybrid scheme is advantageous if the building has too many floors or the required ventilation flow rate is beyond the one that pure buoyancy-driven ventilation schemes can assist. A dimensionless design approach is developed using simplified mathematical analysis. The expressions for the optimal interface between the NVFs (naturally ventilated floors) and MVFs (mechanically ventilated floors) and the vent sizes of different NVFs, which guarantee an appropriate balance between the desired ventilation flow rate, room air temperature, and the heat inputs within the occupants' spaces, are derived. Energy performance analyses are carried out to obtain the dependence manners of the amount of energy consumption to the key design parameters. Differences in the applicability between this hybrid ventilation scheme and the other two low-energy ventilation schemes are presented. The design procedure for this stack-based hybrid ventilation scheme is presented. The dimensionless design approach has been validated with numerical simulations.