Question-and-Answer Resource for the Building Energy Modeling Community
 | 1 | initial version |
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.
| | 2 | No.2 Revision |
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.
UPDATE
Kiva is a standalone simulation tool, but it has been integrated into EnergyPlus as of EP v8.7. You can ask Kiva to calculate ground-contact surface temperatures every timestep by defining Foundation:Kiva and related objects in your EnergyPlus input file ending in IDF.
