Two operating theatres held between 30 and 60 % RH in Helsinki

St. Anne's is two operating rooms at 20–22 °C and ASHRAE 170's 30–60 % RH on a suite handler — 40 % outside air, a chilled-water coil from the modular chiller, an electric heater, a steam humidifier on boiler steam and a fan against 900 Pa of HEPA — and a four-bed recovery ward on a two-pipe fan coil with an 8 kW electric heater.

It needed two things the model did not have: a humidifier kind, and a room humidity floor — the ceiling's inversion on the other bound, the block handed the wettest of its rooms' needs and the humidifier steered to it whatever stage runs. On Helsinki's year the theatres read 0 dry hours and 0 humid hours, 19.9–22.3 °C, eight unmet cooling hours each.

Three sizing lessons came out of the cold year: interior hospital rooms are 0.08 kW/K of envelope, not 0.3 (0.3 was 235 MWh of heating for three rooms); a fan-coil ward with no outside-air path saturates, so the ward carries its own air change; and the theatres' preheat is 120 kW — 60 left them 63 hours short at −2 °C.

What it reads on Helsinki

What it taught

• A humidity floor is a second requirement the controller judges every hour, like the ceiling — not a setpoint on the humidifier.
• A suite handler cannot land one supply state on theatres that cool in January and a ward that heats; the ward gets its own machine.
• Dry hours count while occupied, like unmet hours: an empty theatre's machine starts from off.

The machines

• Example operating-suite AHU, 4 m³/s — open in the builder
• Example fan coil with electric heat, 0.6 m³/s — open in the builder
• Example air-cooled chiller, 90 kW class — open in the builder

Sources

• ANSI/ASHRAE/ASHE Standard 170 (operating-room conditions)
• PVGIS TMY, Helsinki

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.