Relative Humidity control in DesignBuilder

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Thanks mdedoes, it seems like that all-air HVAC systems are more suitable for humidity control. I tried one of the solution (VAV with Reheat) which worked.

However, I am trying to make a list of different type of HVAC systems which can condition closer to the setpoints. I was wondering if other system which doesn't include an air loop (radiative system like heated floor, chilled ceiling or PTAC) can be modified for such control with additional adjustments or combination of different equipment.

Let me know if you have other idea like a local humidification control in zone.

Best, Debayan

Any type of radiant system will only help meet sensible loads, so you'll still need another system for humidity control. Sometimes separating these two can be a good strategy.

From a design perspective, I think your options for humidification are more limited with a PTAC or FCU, rather than a dedicated air handler with a built-in or duct-mounted humidifier.

However, to test these systems for your modeling exercise, I would recommend creating an air loop to act how you want your PTAC/FCU to operate, just because DesignBuilder offers more humidity control options with an air loop.

Thanks mdedoes, I will try out the air loop addition to FCU/PTAC solution.

For the first point, can you let me know which additional humidity control system can be added along with a radiant system (ex: heated floor, boiler hw, nat vent in DB).

You'd need an air system to go along with any radiant-type system (heated floor, chilled ceiling, etc.). Depending on your plant equipment (boilers, chillers, etc.), you could do chilled water cooling with hot water reheat like you mentioned, DX cooling with hot gas reheat, or a different combination. But you're not going to be able to get away from having to wring the water out of the air stream and then reheat it for dehumidification and add water to the air stream for humidification.

Thanks mdedoes, I tried humidity control solution of Unitary Heat Cool system from

https://designbuilder.co.uk/helpv7.0/...

However, after doing all the steps it produces the following error: "Humidifier missing setpoint manager: Air Loop Unitary HeatCool Steam Humidifier". I added the HVAC system in the original question.

Let me know if you know this.