The cost efficiency of improved roof windows in two well-lit nearly zero-energy houses in Copenhagen

Gunnlaug Cecilie Jensen Skarning, Christian Anker Hviid, Svend Svendsen

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Roof windows are efficient and flexible daylight sources that are essential in certain types of houses if theyare to achieve sufficient daylighting throughout. Previous studies have indicated that, for such buildingsto meet nearly zero-energy targets in an easy and robust way without compromising on daylightingand thermal comfort, the thermal properties of roof window glazing, frames and junctions need to beconsiderably improved. However, the barriers to improving roof windows to levels above the current beststandard practice remain great so long as we do not know the economic benefits of such improvements.The aim of this study was to quantify the scope for investing in improved roof window solutions inbuildings insulated to consume nearly zero-energy. Based on two single-family houses in Copenhagenwith typical roof windows and adequate daylighting, the study identified the prices at which various typesof roof window improvements would have to be made available to achieve the same cost efficiency asimproved insulation. If the improvements can be made available for less than these prices, the installationof improved roof windows would make it cheaper to construct well-lit and comfortable nearly zero-energy homes.
Original languageEnglish
JournalEnergy and Buildings
Pages (from-to)399-417
Publication statusPublished - 2017


  • Roof windows
  • Cost-effectiveness
  • Window design
  • Glazing
  • Frame
  • Solar-control coating
  • Space heating
  • Climate-based daylighting
  • Adaptive thermal comfort

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