On a commercial tenant improvement, the mechanical scope is usually the largest single line in the MEP budget and it carries the longest lead times on the whole job. A packaged rooftop unit, a VRF system or a custom air handler ordered late does not delay you by a week — it delays you by months. The crews are rarely the constraint. The equipment is.
The long-lead items
- Packaged rooftop units — standard tonnage can be weeks; high-efficiency, high-static or gas/electric combinations run longer.
- VRF / VRV systems — outdoor units, branch controllers and indoor heads, often the critical path on a tenant improvement with tight ceilings.
- Custom air handlers and DOAS units — built to order, with submittal and approval time before fabrication even starts.
- Large exhaust and makeup-air units — kitchen and lab build-outs live and die by these.
Why late release is so costly
Equipment cannot be set until it arrives, ductwork cannot be fully connected until equipment is set, the system cannot be started until it is connected, and test-and-balance and commissioning cannot begin until it runs. Every week the equipment slips, the back half of the schedule slips with it — and that is the half with the certificate of occupancy on the end.
What keeps it off the critical path
- Run block loads and select equipment off the preliminary plan — not the final permit set.
- Place the equipment order in the first week, refining accessories later by change order if needed.
- Track every unit to a delivery date and report it against the construction schedule.
- Coordinate roof curbs, structural support and crane picks well before the equipment shows up.
Done this way, the equipment is on site when the crews need it, and the mechanical scope stops being the reason the date moves.