Sound intensity probes are often used with windscreens to minimize the effect of noise caused by airflow. A theoretical and experimental study of the effect of windscreens on p-p intensity probes published ten years ago concluded that windscreens give rise to underestimation of the sound intensity at low frequencies in strongly reactive sound fields. The theoretical part of this study was based on the assumption of a windscreen of infinite extent. In this paper windscreens of realistic size and shape are dealt with by means of a coupled boundary element model for the windscreen and the surrounding air. The error of the estimated intensity caused by the windscreen is calculated under a number of sound field conditions of varying reactivity. It is shown that the resulting error can be much larger than the intensity itself in a very reactive sound field. It is also shown that the shape and size of the windscreen has a significant influence on the error.