The AFM says on hot days switching the bleedes to pneumatic OFF, the middle switch selection, can provide extra cooling. So pressurisation is off but cooling is on. If you do that after you have done the before takeoff checks you then don't have a checklist to back up putting them back on. The pilot must adhere to checklist discipline. I won't even comment on the after takeoff checks and the transition checks both calling for a pressurisation check. Inexcusable to miss a cabin climbing at the same rate as the aircraft in those checks (after I just said I won't even comment)