Riverside is the first example building and the one every tier can run: a food court, two retail halls, a screening room and back offices on the DOE Standalone Retail occupancy schedule, 62.1-derived ventilation floors, NREL's moisture capacitance, a 0.012 kg/kg ceiling on every room. AHU-1 is a chilled-water VAV handler with a box per room; its water comes from a chiller block that serves no room and holds 7 °C for it, coupled both ways — the first published building where two machines' solves feed each other, one hour behind.

The coupling is measured against the same machines drawn as one graph: on the temperate year the coupled pair reads 72.8 MWh of coil duty and 48.9 MWh of electricity against the whole plant's 70.8 and 44.6, both meeting the rooms with no unmet cooling hour. That comparison used to run the other way (47.7 against 57.9 MWh), until the coupled chiller stopped calling an hour met at the 9 °C its freeze cutout left in the loop (3 Oct 2026). It now holds its 7 °C whatever the load, where the plant drawn whole lets its water float with the air's requirement, and per kilowatt-hour of cooling the fixed setpoint costs 7 % more electricity. The lag itself is a ±0.3 K limit cycle and half a percent on delivered cooling. What the coupling found on the way was a policy, not a lag: a coil-only block had no way to unload until the valve became the knob.

On London's year the mall reads 19.4 MWh of cooling, 63.9 of heating and 72.6 MWh of electricity — 7.4 of it the chiller's — with no unmet hour in any room. The screening room, shared by the split and the outside-air unit, is held because the outside-air unit is declared the lead: it carries the latent and the split takes the rest.

What it reads on London

Cooling / heating	19.4 MWh / 63.9 MWh
Electricity	72.6 MWh (7.4 the chiller's)
Rooms	no unmet cooling or heating hour; 0–61 humid hours
Coupled vs drawn whole	72.8 vs 70.8 MWh of coil duty, 48.9 vs 44.6 MWh of electricity (temperate year) — 7 % more per kWh of cooling for a chiller that holds its 7 °C

What it taught

• A block coupling carries last hour's state across; for water that is a ±0.3 K limit cycle and half a percent — the lag stands.
• Two machines on one room take it in turn, not in shares: the lead is offered the whole load and the latent, the next what it did not deliver.
• The requirement belongs to the read it is judged against — the room, not the setpoint; 2 000 phantom unmet hours came from the other reading.

The machines

• Chilled-water AHU, 3 m³/s — open in the builder
• Air-cooled chiller, 90 kW class — open in the builder
• DX split, 12 kW class — open in the builder
• Outside-air unit with heat recovery, 0.45 m³/s — open in the builder

Sources

• DOE Commercial Prototype Building Models — Standalone Retail (occupancy schedule)
• ASHRAE 62.1 Table 6.2.2.1 (DCV floors)
• NREL/TP-5500-66515 (effective moisture capacitance)
• PVGIS TMY, London

Readings of the shipped model on the building's own PVGIS typical meteorological year; engineering estimates from catalog data and published correlations. The building runs on every plan, including Free, a few times a day.