Influence of Window Details on the Energy Performance of an nZEB


  • Kristo Kalbe Tallinn University of Technology
  • Targo Kalamees Tallinn University of Technology



energy performance of buildings, nZEB, timber construction, windows, window installation optimisation.


One of the largest sources of heat loss in buildings are the windows. However, windows are alsoimportant to increase solar heat gain and provide daylight. It is necessary to understand how windowdetails influence the energy performance of very energy efficient houses. This is valuable informationfor the design decision making process and may lead to further research or product development. Thispaper examines the influence of window frame thermal transmittance, window frame width and windowinstallation depth on the energy demand of the building. A single-family prefabricated timber nZEBlocated in Estonia was used as a reference building for this study. The results show that decreasing thethermal transmittance and width of the window frame have a remarkable effect on the energy demandof the nZEB (a variation of 42% and 25% respectively). The effect of optimising window installation depthis insignificant (ca 3% variation of heat demand on most of the window placement range and up to 10%of increase in heat demand when comparing the optimal placement to the least effective one). However,it can further improve the energy performance.