On projects with high fresh air rates, such as hospitals and labs, h2x treats incoming fresh air as entering the room at the external temperature. This puts a large heat loss (or gain) on the room, even though in reality the air is preheated or precooled by an AHU or MVHR before it gets there. For example, a room might show around 26 kW of heat loss, when about 25 kW of that belongs on the AHU coil and only around 1.6 kW is left for the room’s FCU. You can currently get accurate numbers through manual workarounds, but they mean copying calculated values back into the model by hand. That gets slow on projects with lots of rooms, and the workarounds don’t work in the new heat gain mode. Proposed solution Add an option on the unit’s heating/cooling settings such as “This unit handles the fresh air load for its rooms.” When it’s enabled: The fresh air load moves from the room to the unit’s coil automatically The room shows its true residual load, and in-room emitters size against that Flow rates stay correct No manual overrides are needed It would also include a supply air temperature field, so the load splits proportionally between the coil and the room. For example, with a room at 21°C, external temperature at 0°C and a 5 kW fresh air loss: Supplied at 21°C: all 5 kW goes to the coil Supplied at 10°C: about 2.4 kW goes to the coil and about 2.6 kW stays on the room Heat gain would work the same way in reverse, and the feature should be supported in the new heat gain mode as well as heat loss.
