Dynamic simulations performed in IESVE were used to assess the performance of a new hybrid demand controlled mechanical extract ventilation (DCMEV) system with an integrated air-to-water heat pump against more traditional HVAC systems.

Energy consultants, 3E, in collaboration with Renson Ventilation completed a performance based analysis in IES Virtual Environment (IESVE) of Renson’s E+ system; a hybrid demand controlled mechanical extract ventilation system with integrated air-to-water heat pump.

The E+ system automatically controls the extract air in functional and habitable rooms to ensure indoor air quality, with the total extract rate mixed with outdoor air as heat source of the air-to-water heat pump. The system is supported by a back-up gas boiler to ensure comfortable temperatures for space heating (SH) and domestic hot water (DHW) are maintained at all times.

Dynamic simulations performed in IESVE were used to compare the performance of the hybrid system against a traditional system of demand controlled mechanical extract ventilation (DCMEV) as well as a mechanical ventilation with heat recovery (MVHR) system combined with a gas boiler. IESVE was used in order to be able to determine the heat pump performance for a typical apartment located in Belgium. The simulation results were also compared against a real life test case in order to validate the results.

The simulations considered two different occupancy scenarios for an apartment with dimensions of 90 m² floor area, 260 m³ volume and 76 m² exposed surface area:

  • First scenario: Occupied by two working adults and two children with a heating set point of 20°C.
  • Second scenario: Occupied by two retired persons spending more of their time at home with a heating set point of 21°C.

Fig 7

By using mixed air as opposed to purely outdoor air as the heat pump source, results showed an increase of the Seasonal Coefficient of Performance (SCOP) of 0.4 for SH and 0.3 for DHW.

Fig 5 & 6

The simulation results also demonstrated that the installation of the hybrid system could reduce up to 31% of annual primary energy demand when compared with the traditional DCMEV system with gas boiler variant for both occupancy schemes, and 16-23% when compared with the standard MHVR system. Both the simulated model and test building returned an 18% recovery of ventilation heat losses towards SH and DHW. While this level of heat recovery is slightly lower than traditional efficiencies of MVHR systems, the hybrid system will ensure that heat recovery occurs during the whole year, not just during the heating season. The coupling of ventilation extract air and heat pumps will also ensure that the dwelling is partly heated by means of renewable energy.

“In order to provide thermal and visual comfort in NZEB buildings, most of our energy concepts are reviewed and optimized with IESVE. The software helps us to model complex building geometry and complicated HVAC systems to provide valuable consultancy services.”

Filip Grillet
Senior Consultant, 3E


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