Study of Residential Thermal Transfer Values (RTTV) and Vertical Daylight Factor (VDF) for Hong Kong

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Original languageEnglish
Article number012032
Journal / PublicationIOP Conference Series: Materials Science and Engineering
Online published19 Aug 2019
Publication statusPublished - 2019


Title9th International SOLARIS Conference, SOLARIS 2018
Period30 - 31 August 2018



In Hong Kong, over one-quarter of the total electricity use was consumed by residential buildings. Recently, the Hong Kong Government issued a practice note namely Design and Construction Requirements for Energy Efficiency of Residential Buildings. This practice note set out the Residential Thermal Transfer Values (RTTV) of building envelopes. To enhance energy efficiency of residential buildings, the RTTV of wall (RTTVwall) and roof (RTTVroof) should not exceed 14 and 4 W/m2, respectively. Being one of the most densely populated cities in the world, most of building developments in Hong Kong are high-rise blocks located in densely built zones. The shading effects due to surrounding buildings could substantially restrict the diffuse light coming from the sky. In 2003, a practice note on lighting and ventilation requirements was issued. Referring to the performance-based approach, the note adopted the vertical daylight factor (VDF) to specify the daylighting performance of the building. The VDF should not be less than 8% for habitable rooms and 4% for domestic kitchens. This paper presents the energy performance of recently designed building fulfills the RTTV requirements. It found that VDF is a good indicator to shows the lighting elecricty consumption in buildings. For most of the bedroom, about 40% of air conditioning and 3 % lighting energy can be saved.

Research Area(s)

  • building façade designs, RTTV, VDF

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