This paper, which is based on a monitored case study, analyses the issues and potential of heat recovery on exhaust air in new multi-family buildings, for combined DHW and SH production by way of heat pumps, in combination with a gas boiler for peak loads. Analysis of the hydraulic diagram, as well as readings of heat and energy meters, allows to point out the causes of an actual HP share (38%) much lower than the projected value (61%), while bringing up the necessity to elaborate standard schemes and sizing rules for such systems.