Major upgrades to the Cooling and Ventilation (CV) infrastructure of ATLAS (Point 1) and CMS (Point 5) are required and constitute a vital part of the HostLab Phase 2 upgrade. This paper describes the main requirements, modifications and upgrades to the CV infrastructure as well as the challenges and safety aspects associated with the installation and commissioning of these CV systems. Two new innovative R744 (CO2) cooling stations managed by CV will act as the primary cooling source for the CO2 cooling system of the ATLAS and CMS inner detectors. Two new buildings (SXSN1/5) will house these primary R744 stations and will require their new dedicated ventilation system. New racks cooled by warmer water than the existing ones will be installed in the SDX1 and SCX5 counting rooms and new Advanced Telecom Computer Architecture (ATCA) racks will be housed in the USA15 service cavern. At Point 5, new cooling towers and their associated water pumping station will cool CMS’s R744 primary cooling stations and SCX5 racks while, at Point 1, two new water cooling stations (chilled and raw water) will increase ATLAS’s chilled water capacity and provide cooling to SDX1 racks. A modification to the existing SF1 cooling tower distribution circuit will supply water cooling to ATLAS’s R744 primary cooling station.
