Reports on the detailed design of Birchensale Middle School, and how the design team has incorporated PROBE lessons into the specification. The school is over 30 years old, naturally ventilated and lightweight in construction. The PROBE team's role has been to help fine-tune the design based on the findings from PROBE post-occupancy studies. Perimeter classrooms are naturally ventilated with cross-ventilation via openable fanlights above the classroom doors. Issues addressed in the specification for the ventilation were: the importance of positive-friction window mechanisms to ensure windows stay open at different degrees of travel; signage near the fanlights above the doors that reinforce the need for the vents to be normally open; a method by which the users of the building know when ventilation is necessary. Simple passive CO2 detectors that darken when CO2 levels are high are planned, to encourage purging of stale air between classes. The window specification is worded in such a way that the contractor must preserve the functionality of the windows. Noise problems via the fanlights were tempered by using bottom-hinged units opening out onto the corridor, to help to bounce noise back down.