Simutation problem with gas boiler and baseboard HVAC

grasshopper honeybee
1

Zero heating consumption with “Baseboard Gas Boiler” HVAC

Hello,

I am carrying out an annual energy simulation of an existing multi-storey building using Rhino 8, Grasshopper and Honeybee. The original project contains confidential company information, so I cannot upload the complete model to a public forum. However, I will describe the workflow and the heating configuration in detail.

General modelling workflow

The building geometry was created in Rhino and divided into thermal zones. In Grasshopper, each thermal zone was generated from a separate closed floor-plan curve using the following workflow:

Curve → Boundary Surface → Move → Extrude → HB Room

Each resulting closed volume was therefore converted into an individual HB Room.

After creating the Rooms, I used the corresponding Honeybee components to solve the adjacencies between neighbouring zones and assign the boundary conditions, apertures, construction sets and program types.

The final processed Rooms were connected to HB Model. Therefore, the Rooms entering HB Model were the final Rooms containing all the assigned energy properties, rather than the original Rooms generated at the beginning of the definition.

Heating schedule and setpoint configuration

The building has heating, but it does not have an active cooling system.

The heating temperature was defined using the following Honeybee components:

HB Weekly Schedule → HB Setpoint → HB Program Type → HB Apply Program Type

First, I created a weekly temperature schedule using HB Weekly Schedule. This schedule represents the building’s weekly heating operation, mainly from Monday to Friday between 09:00 and 14:00.

The values included in this weekly schedule are temperature setpoints. I initially used a heating setpoint of 19 °C.

The output of HB Weekly Schedule was connected to the heating-schedule input of HB Setpoint.

The resulting HB Setpoint was then introduced into the setpoint_ input of each HB Program Type. In this way, each Program Type contained its corresponding heating-temperature schedule.

Afterwards, the Program Types were assigned to the relevant Honeybee Rooms using HB Apply Program Type.

Therefore, the heating setpoint was not entered directly in the HVAC component. It was defined through an HB Weekly Schedule, incorporated into an HB Setpoint, included in each HB Program Type, and finally assigned to the Rooms.

The schedule and setpoint workflow was:

HB Weekly Schedule
→ connected to heating_schedule_ in HB Setpoint
→ HB Setpoint connected to setpoint_ in HB Program Type
→ Program Type assigned to the Rooms with HB Apply Program Type

HVAC configuration

Once the Program Types and heating setpoints had been assigned, I modelled the HVAC system using:

HB HeatCool HVAC → HB Apply HVAC

In HB HeatCool HVAC, I selected the HVAC equipment type:

Baseboard Gas Boiler

This template was selected because the real building is heated by a gas boiler supplying baseboard/radiator terminal units.

The output of HB HeatCool HVAC was connected to the hvac_ input of HB Apply HVAC. The Honeybee Rooms that already contained their Program Types, weekly heating schedules and setpoints were connected to the Rooms input of HB Apply HVAC.

The Rooms resulting from HB Apply HVAC were then connected to HB Model.

The complete energy-property workflow was therefore:

HB Rooms
→ HB Apply Program Type
→ HB Apply HVAC
→ HB Model
→ HB Model to osm

→ annual OpenStudio/EnergyPlus simulation

The HB Apply HVAC component received the HVAC system generated with HB HeatCool HVAC, configured as Baseboard Gas Boiler.

Problem encountered

The annual simulation finishes and produces energy results, but the reported heating consumption is zero.

This does not seem physically reasonable because:

  • The weather file corresponds to Oviedo, Spain.

  • The Rooms have heating-temperature schedules assigned.

  • The weekly heating schedule is connected to the heating input of HB Setpoint.

  • Each HB Setpoint is included in the corresponding HB Program Type.

  • The Program Types are assigned to the Rooms.

  • A Baseboard Gas Boiler system is created with HB HeatCool HVAC.

  • The HVAC system is assigned to the Rooms using HB Apply HVAC.

  • The Rooms coming from HB Apply HVAC are connected to the final HB Model.

Could you please clarify the following?

  1. Is this the correct procedure for assigning a weekly heating-temperature schedule to each Program Type?

  2. Is it correct to leave the cooling-schedule input of HB Setpoint empty or with a very high setpoint (so cooling never occurs) when the building has no cooling?

  3. Is the Baseboard Gas Boiler template appropriate for modelling a central gas boiler supplying baseboard or radiator terminals?

  4. How can I verify that the HB Setpoint and its heating schedule have been correctly inherited by every Room?

  5. How can I verify that HB Apply HVAC has successfully assigned the Baseboard Gas Boiler system to all the Rooms?

The software versions used are:

  • Rhino 8

  • Ladybug Tools 1.10.33

  • Honeybee Core 1.64.41

  • OpenStudio Application 1.11.0

  • EnergyPlus 25.1.0

I can provide screenshots of the Grasshopper components, their connections and their input values if necessary, but I cannot publicly share the original building geometry or the complete project because it contains confidential company information.

Thank you very much for your help.