The airtightness and condensation risk analysis will have been worked out at the design stage and these will need to be followed to the letter. Something to remember is that airtightness is as much about sealing up the building as it is about managing moisture and not allowing it to build up.
Different building methods and applications will require a different approach to airtightness, and different use of products. In some cases your builder may offer an alternative means of achieving the same end result; in that case your energy assessor needs to approve the changes and create a new set of plans for everyone to follow on site.
On commercial buildings, airtightness inspectors are alerted when an opening has to be made in the airtightness membrane so as to ensure it is sealed back up effectively. On a self-build project, you will have to make it clear to all tradesmen any cut to the membrane needs to be flagged to you or your builder.
You will need to keep an eye on things on site if going direct labour; if you have hired a main contractor they will keep on top of this element.