Exploring the potential for natural ventilation of very tall buildings

Tall buildings have traditionally been sealed andmechanical ventilated. In recent years advanceshave been made allowing the natural ventilationof tall buildings for a part of the year. Themotivation has been both energy savings andoccupant comfort. The projects realized thus farwork on the mixed mode principle. Naturalventilation is employed for a proportion of theannual period. However under certain wind andexternal temperature conditions mechanicalsystems take over. Whilst this means ofoperation allows energy savings in operationand improves occupant comfort, recent researchhas shown that there are in most cases no realsavings in total primary energy consumptionand that the economic viability of theseconcepts is poor; the reason being largely due tothe fact that such concepts provide two systemsessentially performing the same task; a situationwhich rarely maltes economic or ecologicalsense. If a system of natural ventilation could berefined so as to perform in an acceptable way allyear round and mechanical ventilation systemsthus dispensed with, a paradigm shift in theecological and economic viability of naturallyventilated tall buildings would occur. This paperillustrates a concept which allows all year roundcontrolled natural ventilation of very tallbuildings and outlines the implications for thearchitectural design of such buildings.