Unrealistically high heat gains by ventilation for an open window with screen

[jelgerjansen]

@flosfeld reported the following:

Concerning IDEAS.Buildings.Components.Window, I observed a high heat gain by ventilation for an open window with screen. This occurs when having 2 way flow, when the inflow is of the same magnitude as the outflow. The unexpected heat gain is caused by TShaScreen, which is to high. Reason for this is the variable m_flow, since this is the net value of flow received from outsideAir. In this case, the net flow value is close to 0, although it is both the inflow and outflow that should be taken into account.