The fan door does not care about your drawings. It pressurises the house and tells you the truth in air changes per hour, and at Long Barn the truth was 0.9 when we had promised 0.6. Somewhere, the barn was breathing where it should not.
Three days with a smoke pencil found it: a single service penetration behind the kitchen units, sleeved but not sealed, hidden by the one run of pipework that went in on a Friday. We opened the wall, taped it properly, and retested at 0.54. The lesson is not about tape. It is about Fridays.