Ventilation of air-conditioned residential buildings: A case study in Hong Kong

Z. T. Ai, Cheuk Ming Mak, D. J. Cui, P. Xue

Research output: Journal article publicationJournal articleAcademic researchpeer-review

47 Citations (Scopus)


More and more studies reported that there were insufficient ventilation and excessive CO2concentration in air-conditioned residential buildings, but few solutions were provided. This study investigates the overnight evolution of CO2concentration in air-conditioned residential buildings and then focuses mainly on the evaluation of three ventilation strategies, including overnight natural ventilation, short-term mechanical ventilation and short-term natural ventilation. On-site measurements were conducted in a typical residential bedroom in Hong Kong in September. The indoor and outdoor CO2concentration, air temperature and relative humidity as well as the outdoor wind speed during the measurements were analysed. Ventilation rates were calculated based on the time series of CO2concentration. This study confirms that additional ventilation is usually needed in air-conditioned residential buildings. Overnight natural ventilation with even a small opening is associated with excessive energy consumption and deteriorated indoor thermal environment. Short-term natural ventilation strategies are inefficient and uncontrollable. Compared to the best short-term natural ventilation strategy, a reasonably designed short-term mechanical ventilation strategy requires only a 41% of ventilation period to complete one full replacement of indoor air and to reach a lower indoor CO2concentration. Nighttime case studies and a theoretical analysis suggest that a few several-minute mechanical ventilation periods could potentially maintain an acceptable indoor air quality for a normal sleeping period of 8 h.
Original languageEnglish
Pages (from-to)116-127
Number of pages12
JournalEnergy and Buildings
Publication statusPublished - 1 Sept 2016


  • Carbon dioxide (CO ) 2
  • On-site measurements
  • Residential buildings
  • Room air conditioner
  • Ventilation

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • Mechanical Engineering
  • Electrical and Electronic Engineering


Dive into the research topics of 'Ventilation of air-conditioned residential buildings: A case study in Hong Kong'. Together they form a unique fingerprint.

Cite this