Cold bridges are usually at edges
The middle of a wall is easy to insulate. Floor perimeters, steel beams, lintels, roof edges and window reveals need more thought because structure interrupts the insulation layer.
More insulation changes construction thickness
High-performance floors and roofs can be deep. If this is not allowed for early, finished floor levels, ceiling heights and external thresholds can end up wrong.
Ventilation still matters
Making a room more airtight increases the need for deliberate ventilation. Kitchens, bathrooms and utility rooms need suitable extract arrangements.