Positive insulation is a layer insulation that implements in such a way that it prevents the leaked water from entering the structural element, and this element remains intact. As for the passive insulation when the leaked water has entered the structural element, it has been saturated with it and may have destroyed it, as the function of negative isolation is to prevent this water from leaving the other end of the structural element to  protect the layer that covers it (cement, paint, and possibly other elements) from the negative impact of this water.