Balancing energy and daylighting performances for envelope design: A new index and proposition of a case study in Hong Kong

Jing Chao Xie, Peng Xue, Cheuk Ming Mak, Jia Ping Liu

Research output: Journal article publicationJournal articleAcademic researchpeer-review

17 Citations (Scopus)


Daylight is an influential factor with the characteristics of both photometry and radiometry. Irradiance brings solar heat gains that transfer to building cooling load, while illuminance provides a luminous environment and affects artificial lighting system at the same time. To balance the energy and daylighting performances, it is reasonable to minimize the environmental load under moderate comfort conditions. This study first quantified luminous comfort with a dynamic daylighting metric, average daylight autonomy (Ave. DA300), from a questionnaire survey and simulation work. The benchmark of this metric should range from 29.6% to 57.8% for high-rise residential buildings. With this guideline, the Hong Kong public housing units is found that part of units lack of daylight due to the high building floor and density, while some units have potential to save energy by compromising daylighting performance. Therefore, a new index, energy daylight rate (EDR), is proposed to help decide the best scenario of envelope design for both daylighting and shading purposes. The results show that opening a secondary window is an efficient way to bring more light in and lengthening overhang is an efficient way to block excessive sunlight. This method and the new index are proved to have the ability to help defining proper building envelope design at the early stage.
Original languageEnglish
Pages (from-to)13-22
Number of pages10
JournalApplied Energy
Publication statusPublished - 1 Jan 2017


  • Daylight autonomy
  • Energy daylight rate
  • Energy saving
  • Envelope design
  • Luminous environment

ASJC Scopus subject areas

  • Civil and Structural Engineering
  • Building and Construction
  • General Energy
  • Mechanical Engineering
  • Management, Monitoring, Policy and Law


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