Problem with Ideal Loads
I’m trying to verify whether my EnergyPlus/OpenStudio model is behaving correctly, and I would really appreciate some help. I’m comparing my results with another building simulation tool, and the numbers I’m getting are significantly different even though the constructions and general assumptions are the same.
The building is a well-insulated residential house.
Exterior walls have U-values below 0.40 W/m²K,
Windows have U ≈ 1.2 W/m²K,
SHGC in my EnergyPlus model is set to 0.45.
In the other software, with the exact same constructions and the same thermostat setpoints, I consistently get around 22 kW peak heating load and around 18 kW peak cooling load. These values match the expected performance for this location and climate. This programme is without schedules, with constant loads for people, lighting, equipment.
However, in my EnergyPlus model (using Ideal Air Loads), I get much lower loads. Even when I increase infiltration in the living room to 2 ACH to approximate natural ventilation through open windows, my heating load is still much lower than in the other tool. If I reduce infiltration to more realistic values (0.3–0.5 ACH), the heating load drops even more, to the point where it looks unrealistically low.
In the other simulation tool, those 22 kW heating and 18 kW cooling results were obtained with only 0.5 ACH for living spaces, so I’m confused why EnergyPlus gives drastically different results even when I set higher infiltration.
I have checked:
Constructions (same layers and U-values in both tools)
Window SHGC = 0.55
Thermostat setpoints (identical in both models)
Weather files (slightly different outdoor temperatures, but only by a few degrees — not enough to explain such a large deviation)
Still, the total gains and losses in EnergyPlus look very different from the other program, and the distribution of loads across the building is also not similar.
I also included some surrounding trees in the OpenStudio model but they can easily be removed if needed — I can upload the OSM if anyone wants to take a look.
I would be extremely grateful if someone could check what I might be doing wrong or whether there is a fundamental modeling difference that I am missing.
Thank you in advance
