Utilization of Window System as Exhaust Air Heat Recovery Device and Its Energy Performance Evaluation: A Comparative Study

The exhaust air glass unit (EAGU) can be treated as an integration of multilayer glazing unit and heat recovery device to utilize the exhaust air from conditioned space with a fresh air ventilation system to improve the thermal performance of window system. However, compared with the conventionally used mechanical ventilation with a heat recovery (MVHR) system, whether the use of EAGU is energy-efficient or not has not been estimated. In this paper, a numerical model, validated by experimental measurement, was used to calculate the hourly cooling and heating loads and annual energy demand of EAGU. This study compared the annual energy performance of EAGU and MVHR under various conditions, and further discusses the applicability of EAGU for different climates. The results indicate that the energy saving potential of EAGU ranges from 26.8% to 38.2% for different climate conditions. In the cooling season, the energy saving potential of EAGU performed much better than that of the commonly used MVHR. However, the EAGU was inferior to the MVHR in the heating season. Moreover, the EAGU is more suitable for application in warm climates, rather than cold climates. This study can provide some application guidelines about the selection of exhaust air heat recovery devices for maximizing the energy saving potential