Optimal daylight factor for energy-efficient toplighting system

Younju Yoon, William P. Bahnfleth, Martin Moeck, Richard G. Mistrick

Research output: Contribution to journalConference articlepeer-review


Skylights can introduce considerable heat gain and loss that may offset the benefits of electric light savings and cause an increase in yearly net energy use. The design of a toplight system needs to take into consideration different toplighting types, including aperture size and orientation, electric lighting control, and, most importantly, the local climate. This study examines the impacts of aperture size (day light factor) for four combinations of toplighting strategies and glazing types on the total yearly energy loads for a prototypical open office space situated in four different climates. This study shows that toplighting systems designed to meet a 2% daylight factor are not optimal. The optimum daylight factor varies depending on toplighting type, local climate, and the thermal and solar heat gain properties of the glazing.

Original languageEnglish (US)
Pages (from-to)622-632
Number of pages11
JournalASHRAE Transactions
Volume112 PART 2
StatePublished - Oct 31 2006
Event2006 Annual Meeting of the American Society of Heating, Refrigerating and Air-Conditioning Engineers, ASHRAE - Quebec City, QC, Canada
Duration: Jun 24 2005Jun 28 2005

All Science Journal Classification (ASJC) codes

  • Building and Construction
  • Mechanical Engineering


Dive into the research topics of 'Optimal daylight factor for energy-efficient toplighting system'. Together they form a unique fingerprint.

Cite this