Efficiency of a double block cross flow balanced ventilation system with heat recovery.

In Amstelveen, The Netherlands, an apartment complex of forty two units has been build. Sixteen units are extreme low energy apartments. These apartments are very well isolated and have air tight facades. Moreover, they are equipped with solar collectors for the domestic hot water system, a high efficiency boiler for space heating and additional heating of the domestic hot water, automatic controlled sun shading devices, a balanced ventilation system with heat recovery and an advanced control system that controls the indoor climate, the mechanical ventilation and the sun shades according to the measured indoor temperature and outdoor climate. In the winter the apartments use air from the atrium which is always some degrees higher than the outdoor air. The balanced ventilation system with heat recovery will be discussed in this paper. Before the units are installed in the apartments, one is tested in the laboratory of the Delft University of Technology. Depending on the climatological conditions, the efficiency of the heat recovery unit is between 72.1 %  to 84.5%. The yield factor, when the recovered heat from the ventilator is also accounted for, is approximately 5% higher, between 78.5%  to 88.5%. By an average atrium temperature of 5 °C it is possible to recover approximately 115 .m gas-equivalent annually from the exhaust air.