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.
Natural ventilation is being applied to an increasing number of new buildings to minimise reliance on mechanical ventilation and so reduce emission of greenhouse gases. However, passive stack ventilation (PSV) systems are currently designed without incorporating heat recovery leading to significant wastage of energy. Heat recovery systems have not been used in naturally-ventilated buildings because the pressure loss caused by a conventional heat exchanger is large compared to the stack pressure and could cause the ventilation system to fail.
Since 1985 more than 170 very low energy houses, all of the same type and structure, were built in the Flemish Region, Belgium. Because conduction losses are very low, mean Urn-value 0.30-0.35 W/(m².K), ventilation losses become very important, up to 45% of the heat losses if no heat recovery is utilised. Three of the houses were monitored in detail for energy consumption, energy and ventilation efficiency. All houses are equipped with the same ventilation system: balanced mechanical ventilation with heat recovery.
The research community as well as the design and construction practice is spending a lot of efforts and investments in developing systems which optimise the energy use for achieving certain specified air flow rates. For example, improvements in efficiencies of 10 % in heat recovery systems would be considered as remarkable. At present, one observes a tremendous difference in the ventilation requirements in various countries as well as at the European level.
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