Performance of Balanced Ventilation with Heat Recovery in Residential Buildings in a Cold Climate

This study simulated the performance of various mechanical supply and exhaust ventilation systems, incorporating heat recovery, in a typical Finnish residential apartment building. Dynamic thermal simulations were undertaken, representing a period of a year. These simulations incorporated the building details combined with information about the HVAC-systems, internal thermal loads and outdoor climate. The ventilation systems investigated included a simple centralised constant air volume (CAV) mechanical supply and exhaust ventilation system and a decentralised air handling unit that included an option for variable air volume (VAV) for demand-controlled ventilation. Energy consumption, thermal comfort, indoor air quality, pressure conditions, and air infiltration flows were simulated. It is shown that, in the cold climate studied, energy efficiency in a residential apartment building can be improved remarkably by using a ventilation heat recovery system. Results show that a traditional exhaust ventilation system can use up to 67% more energy than a heat recovery system having 80% efficiency and 41% more energy than a heat recovery system having 60% energy recovery efficiency. Increasing the heat recovery efficiency from 60 to 80% was approximately as effective an energy saving measure as using demand-controlled VAV. A simple centralised CAV ventilation system with 60% heat recovery efficiency proved to be particularly energy efficient because of low electricity consumption. The decentralised ventilation system did not show a clearly improved energy performance, because of the relatively high electricity consumption of the fans and electrical reheating coils used. However, it allowed a reduction in the district heat consumption by means of higher heat recovery efficiency and VAV control.