eesti teaduste
akadeemia kirjastus
Estonian Journal of Engineering
Nearly zero energy office building without conventional heating; pp. 309–328
PDF | doi: 10.3176/eng.2013.4.06

Martin Thalfeldt, Jarek Kurnitski, Alo Mikola

A case study of the first nearly zero energy office building (nZEB) in Rakvere, Estonia was conducted to determine whether an office building can be built without a conventional space heating system while ensuring adequate thermal comfort in the offices. Energy and indoor climate simulations of alternative solutions were carried out and the feasibility of the solutions, ensuring heated rooms throughout the year, was assessed based on investment cost and payback calculations. The results showed that despite of the low heat losses, a nZEB still needs a space heating system with room based temperature control. Heating needs primarily occurred during weekends and at night; however, without space heating the air temperatures in the rooms dropped down to 16.7 °C during occupancy and were below 21 °C during about 700 occupied hours. Supply air heating with variable air volume system, controlled according to the coldest room and on demand night operation, was able to keep + 21 °C temperature in all rooms, but resulted in significant energy penalty caused by overheating of offices with lower heat losses and increased fan electricity use. The economic analysis showed that a building with simple constant air volume ventilation system and radiator heating was most feasible. The investment cost increase of the variable air flow ventilation system was too high compared to the savings in energy cost that was already low.


  1. About passive house – what is a passive house? 01_whatisapassivehouse/01_whatisapassivehouse.htm

  2. Feist, W., Schnieders, J., Dorer, V. and Haas, A. Re-inventing air heating: Convenient and comfortable within the frame of Passive House concept. Energy Build., 2005, 37, 1186–1203.

  3. Krajcik, M., Simone, A. and Olesen, B. W. Air distribution and ventilation effectiveness in an occupied room heated by warm air. Energy Build., 2012, 55, 94–101.

  4. Fernandez-Gonzales, A. Analysis of the thermal performance and comfort conditions produced by five different passive solar heating strategies in the United States midwest. Solar Energy, 2007, 81, 581–593.

  5. Krüger, E. and Givoni, B. Thermal monitoring and indoor temperature predictions in a passive solar building in an arid environment. Build. Environ., 2008, 43, 1792–1804.

  6. Georges, L., Berner, M., Berge, M. and Mathiesin, H. M. Analysis of the air heating in Norwegian passive houses using detailed simulations. In Proceedings 13th International Conference of IBPSA. Chambery, France, 2013.

  7. Isaksson, C. and Karlsson, F. Indoor climate in low-energy houses – an interdisciplinary investigation. Build. Environ., 2006, 41, 1678–1690.

  8. Rohdin, P., Molin, A. and Moshfegh, B. Experiences from nine passive houses in Sweden – indoor thermal environment and energy use. Build. Environ., 2013,

  9. McLeod, R. S., Hopfe, C. and Kwan, A. An investigation into future performance and over­heating risks in Passivhaus dwellings. Build. Environ., 2013, 70, 189–209.

10. Estonian Government Ordinance No. 68. Energiatõhususe miinimumnõuded (Minimum require­ments for energy performance of buildings) 30.08.2012. Riigi Teataja, I, 05.09.2012, 4.

11. Beck, W., Dolmans, D., Dutoo, G., Hall, A. and Seppänen, O. Solar Shading. REHVA Guide­book 12. Forssa, Finland, 2010.

12. IDA-ICE, IDA Indoor Climate and Energy 4.5.

13. Kalamees, T. and Kurnitski, J. Estonian test reference year for energy calculations. Proc. Estonian Acad. Sci., Eng., 2006, 12, 40–58.

14. BS EN 15251:2007. Indoor environmental input parameters for design and assessment of energy performance of buildings- addressing indoor air quality, thermal environment, lighting and acoustics.


Back to Issue

Back issues