Ventilation and heating systems: Watchpoints
A set of plans for all ducting will have been issued to you by the company who will be installing the ventilation system. If you plan to install it yourself, you will need a mechanical and electrical (M&E) engineer to step in and supply a set of plans for the ducting: minimal pipe runs, minimal number of bends. You will also need advice on installation and get them to do the commissioning, all of this at a cost.
In ROI commissioning on all domestic ventilation systems has to be done by an independent person, i.e. the 2019 building regulations state it can no longer be the ventilation company that signs off on it.
In NI, the installers will provide the certification, but your certifier will also need to check that the installation is in accordance with the manufacturers instructions.