Heating Systems: User Friendly Heating Systems for Low-energy- and Passive-houses

The main goal of this project was the development of a comprehensive evaluation method for heating systems for buildings insulated according to passivehouse criteria.


Austrian Federal Ministry of Transport, Innovation and Technology



  • Institute for Thermal Engineering, Graz University (project leader)
  • Society for Renewable Energy  

Two passivehouses which were energetically monitored within the EC-project CEPHEUS were simulated in TRNSYS. The results were compared to the measurements and a sensitivity analysis of various parameters for the simulation compared to the measured room temperature course was undertaken.

A set of user behaviour patterns (ventilation, room temperature, presence, internal gains ..) was developed using a questionnaire in 53 apartments of low-energy multi family buildings, the measurements in the EC-project CEPHEUS, and an additional literature research. Using these data two reference multi family buildings, insulated according to passivehouse criteria, were set up for the simulation.

Following this, nine different heating systems for such buildings (4 air heating and 5 water heating systems) with the heat sources decentralized air/air/water heat pump, central ground coupled heat pump, central pellets or gas burner, and decentralized pellets or tiled stove were described and qualitatively analyzed.

Four out of these systems (decentralized air/air/water heat pump, centralized ground coupled brine/water heat pump, centralized gas- and pellets burner, all centralized systems using two-pipe heat distribution systems) were simulated in detail using the simulation tool TRNSYS. They were compared according to end-use and primary energy demand, CO2-equivalent emissions, heat delivery costs (including capital costs), and their sensitivity for changing user behaviour.

Additionally a sociological analysis using questionnaires and additional literature review was undertaken to evaluate the user demand and user acceptance for the various heating and heat delivery systems.