OpenStudio: Extremely high cooling load compared to heating load in a cold climate (Rochester, MN, Zone 6A)

grasshopper honeybee
1

Hello everyone,

I’m a university architecture student working on a building energy simulation project using OpenStudio and EnergyPlus.

I’m experiencing an unusual result: the annual cooling load is approximately 19.6 times higher than the heating load, even though my building is located in Rochester, Minnesota (ASHRAE Climate Zone 6A, Cold-Humid).

I’m trying to determine whether this is caused by incorrect model settings or by the building’s internal heat gains and envelope characteristics.

1. Model information

  • Location: Rochester, Minnesota, USA (Climate Zone 6A)

  • Weather data: TMYx 2011–2025 EPW

  • Building type: Two-story educational and research facility

  • Total floor area: Approximately 4,508 m²

  • Window-to-wall ratio: 40%

  • Space Types: ASHRAE 90.1-2019 College (Classroom, Office, Laboratory, Corridor, Restroom, Stairs)

  • HVAC: Ideal Air Loads

  • Construction Sets: College-based construction sets

The intended thermostat schedule is:

  • Weekdays, 08:00–20:00: Heating 21°C / Cooling 24°C

  • Weekday nights: Heating 15°C / Cooling 27°C

  • Weekends: Heating 15°C / Cooling 28°C

I have not yet fully verified whether the actual thermostat schedules and HVAC settings are correctly applied to every thermal zone.

2. Simulation results

The OpenStudio Results report shows:

  • Annual cooling load: 294,572.54 kWh

  • Annual heating load: 15,051.15 kWh

  • Cooling-to-heating ratio: 19.57:1

Some unusual monthly results:

Month Average outdoor temperature Cooling load Heating load
January -7.9°C 13,609 kWh 5,197 kWh
February -8.8°C 14,492 kWh 4,255 kWh
July 22.3°C 22,950 kWh 0 kWh
September 17.2°C 37,040 kWh 0.61 kWh

Cooling demand is higher than heating demand even during the coldest winter months. September also has a much higher cooling load than July.

3. What I have checked

In OpenStudio:

  • Design Specification Outdoor Air objects are assigned to all College Space Types.

  • For the Office Space Type, the outdoor airflow per person is approximately 0.00236 m³/s-person.

  • Space Infiltration Design Flow Rate fields are empty in both Space Types and individual Spaces.

  • Space Types and Thermal Zones appear to be assigned to the appropriate rooms.

  • I have not yet confirmed whether the outside boundary conditions, internal loads, and Ideal Air Loads outdoor-air settings are all correct.

I also tested the model using a much colder weather file (Verkhoyansk, Russia) as a diagnostic comparison. The heating load increased substantially, but cooling loads remained significant.

4. My questions

  1. Is such a high cooling-to-heating load ratio plausible for an educational building in Climate Zone 6A?

  2. Could missing infiltration objects cause the heating load to be severely underestimated?

  3. Does the Ideal Air Loads system automatically account for the outdoor air specified in the Space Types, or are additional settings required?

  4. Could incorrectly assigned outside boundary conditions (such as Adiabatic instead of Outdoors) explain this behavior?

  5. Which EnergyPlus output variables or OpenStudio settings should I inspect first to identify the source of the excessive cooling load?

I would really appreciate any guidance on diagnosing this issue.

I can provide screenshots of the monthly load profiles and relevant OpenStudio settings, as well as the OSM model file if needed.

Thank you very much for your help!