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# How is the ground temperature calculated in EnergyPlus?

May I ask how the monthly ground temperature is calculated in EnergyPlus?

What is the depth of soil where the ground temperature is measured?

Thank you!

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During an EnergyPlus simulation, monthly ground temperatures are NOT calculated, but set as an input by the user. Monthly "undisturbed" ground temperatures found in the STAT file for each location should NOT be used for ground-contact surfaces of conditioned spaces. These ground temperatures should be used for specific applications according to depth. For example, Site:GroundTemperature:Shallow is for 0.5-m depth and should interact with surface ground heat exchanger objects.

EnergyPlus does have auxiliary programs that can be simulated independent of the IDF file and determine detailed ground heat exchange depending upon if the model has a Slab or a Basement. These programs will model ground heat exchange for ground contact surfaces and produce monthly ground-contact surface temperatures, either as core and perimeter or as an average across the surface. These temperatures need to be transcribed into your IDF file.

If you come across a situation where the Slab and Basement auxiliary programs can't model your specific situation (insulation placement, insulation amount, etc.), you could try to use Kiva. Kiva is an open-source ground heat transfer modeling tool developed by @Neal Kruis at Big Ladder Software (DISCLAIMER: he is my colleague). You can download it for free HERE.

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