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Activity modeling for energy-efficient design of new hospitals


Background: Buildings in Europe counts for 40% of primary energy consumption. Among
different building categories like offices, dwellings and so on, hospitals are one of the two
most energy-intensive. This article reports some of the results from the “Low Energy
Hospitals” project supported by the Norwegian Research Council (NRC) and the participating
companies. The aim is to show how energy use in hospitals could be reduced by 50 %. Many
projects are running in Norway and the rest of the world aimed at improving energy
performance in buildings. This project focusses on hospitals in particular. The main thesis is
that if the diversity of functional areas within a hospital is better understood by the design
team, and if energy becomes an integrated part of the early planning of hospitals, then a
halving of consumption is attainable by delivering and recycling energy according to the
changing activity levels in each area.
Method: The data was collected from three hospitals in the South-East hospital region of
Norway, giving actual data on energy use, occupancy, and clinical activities on an hourly
basis. These data were used to make an activity profile, telling which activity is occurring in
different parts of the hospitals. Patient register data was used together with interviews to find
out when personnel were present. Design data for hospital technical systems in the various
areas was also collected. Norwegian hospitals categorize their area into specific functional
areas, such as bed wards, offices, operating theatres and so forth; this was used by the project
to characterize energy performance.
Result: The activity data clearly show that hospitals are not operated 24 hours 7 days a week;
only a small percentage of floor area is used around the clock, and more than half of hospital
area follows normal office hours. Even during active hours the simultaneous occupancy level
was relatively low. This activity demand was not reflected in the energy data, which showed a
large and continuous base-load for electrical and ventilation energy. A review of the design
data confirmed how hospitals differ from all other building categories: (1) larger internal
loads from hospital-specific equipment using high-value electricity, whose waste heat also
demands cooling energy (2) large ventilation demand coupled with lower rate of heat
recovery due to unnecessarily strict hygiene requirements.
Conclusion: Hospital equipment and ventilation designs did not allow energy supply to
follow the actual demand from activity, and that the reduction potential is about 50%. We
propose activity modeling as an integrated design method to evaluate new designs for
demand-control of hospital equipment and ventilation energy.


Academic article




  • Tarald Rohde
  • Robert Martinez
  • Mads Mysen


  • SINTEF Digital / Health Research
  • Norconsult AS
  • SINTEF Community / Architectural Engineering



Published in

International Journal of Facility Management







View this publication at Cristin