Cooling only when room is occupied


I have been modeling cooling for a building, where only bedrooms have air-conditioners, and are only occupied during the night. When run with a simple set-point value for the room, the cooling unit seems to be running all the time, and has cooling energy demand even when the room is unoccupied. Is there a way to only switch on cooling when the room is occupied? I tried implementing the program after the setpoint, but that does not seem to be overriding the cooling all the time problem.

Secondly, I also created a cooling schedule for the setpoint input to the room program. However, in spite of ensuring it is similar in structure to the default program’s setpoint values, the simulations never seem to have any cooling energy demand, and on investigation the HVAC system never turns on, leaving the room hot. What am I doing wrong? I have attached a screenshot of the schedule created, and the grasshopper file, and the section “Room program - bedrooms” has this custom schedule. (444.9 KB)


Hi, @aishuiyer1

First, as far as I know, there is no GH component for an on/off schedule to set the availability for a HVAC system unless it is a ideal air system. So, you can use the “HB Setpoint” component to set the availability schedule for your “Window AC with no heat system”, as you did in your file.

But the “HB Constant Schedule” component you used may be not suitable for your situation. According to your approach, this schedule refers to the fact that the setpoint is a constant, 27 degrees Celsius, for 8760 hours of the year. Therefore, I suggest that you can use the “HB Weekly Schedule” component for your function: you can specify a different setpoint for each day of the week.

You can set a setpoint when the rooms are occupied (for example, 27 ℃); And when no one is around, set a very high value (such as 100 ℃).

I hope it can help you solve this problem.

And secondly, I run the simulation with the .epw file also from mumbai, but it shown that your HVAC system has cooled the room and I can also have the cooling energy result.


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Hi @S_hertz ,

Thank you for your detailed response.

I am attaching the grasshopper file here with the setpoint schedule like you suggested (weekly) with the higher temperatures for hours when I do not want the HVAC system to work. It still does not output any cooling demand, and does not seem to have the HVAC system operational. Could you please help me out? Did it work for you with the constant schedule or the variable one? (449.3 KB)

Thank you,

I met the same problem recently, I use the “HB Constant Schedule” and “HB Sensonal Schedule” component to set “HB Setpoint” component then attach it to “HB ProgramType” component, but the “HB Annual Loads” component does not output any heating or cooling demand.
But when I use the setpoint data from “HB search programs” component, the “HB Annual Loads” component works well, so I think may be the way to set the setpoint schedule is inappropriate.
Have you solved this problem? I would appreciate it if you can give me some advice.
Thank you,

Hi @Rice ,

Your screenshots show that you’re not using the HB Seasonal Schedule and I would recommend that you read the component input descriptions carefully.