The future of hybrid ventilation in office buildings – energy simulations and lifecycle cost

This study presents a comparison of three ventilation systems; automated Natural Ventilation (NV), balanced Mechanical Ventilation (MV) with heat recovery and Hybrid Ventilation (HV) with heat recovery for a new build office building.
The energy demand for heating and electricity as well as the indoor climate of the building were simulated using IESVE. Three key European cities were selected (Copenhagen, Munich and London) in order to investigate the applicability of the principles to different climatic conditions in Europe.
Ventilation control strategies were set to achieve identical indoor climate for all three ventilation system. Thermal comfort and indoor air quality targets were set according to Category II of the European Standard EN 15251 (EN 15251, 2007).
The results show that the total primary energy demand (sum of heating and fan electricity demand multiplied by the primary energy factors) for NV was 9-11 kWh/m2/year, MV 20-25 kWh/m2/year and HV 7-8.5 kWh/m2/year. HV enables energy savings of 20-25% compared with NV and 60-70% compared with MV.
The total investment of the different systems including capital cost (products and installation), operation (electricity and heating), and maintenance was investigated for a 20 year period. Overall NV was found 4 to 5 times cheaper compared to MV and HV was found 2.5 times cheaper than the MV system.
The results demonstrate that HV should be considered for offices in addition to NV and MV. Overall the HV solution reduced the energy demand for heating and electricity and saved up to 60% of the CO2 emissions compared to the NV and MV.