Ground temperature in openstudio

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After some reading in the Engineering Reference I decided that for my application (Residential) a good solution would be to use the Foundation Kiva, Rather then setting the ground temperature to the average monthly air temperature. The Input Output Reference is stating:

Caution: The “undisturbed” ground temperatures calculated by the weather converter should not be used in building losses but are appropriate to be used in the Site:GroundTemperature:Shallow and Site:GroundTemperature:Deep objects. The reasoning (for building losses) is that these values are too extreme for the soil under a conditioned building. For best results, use the Slab or Basement program described in this document to calculate custom monthly average ground temperatures (see the Ground Heat Transfer section). This is especially important for residential applications and very small buildings. If one of these ground temperature preprocessors is not used, for typical commercial buildings in the USA, a reasonable default value is 2C less than the average indoor space temperature.

You can read about the theory behind Foundation Kiva in the Engineering Reference from page 144 and on. You are welcome to use the E+ Measures I wrote to include Foundation Kiva and for Kiva settings at your own risk.

Hey, I have the same problem, but I don't know where I have to add the code above? Could someone explain in a more detailed way, what I should do to change the ground temp with this code?

Greetings :)

You could try using the following code, but I have set only a single input variable that will set the temperature for the entire year. Monthly variation has not been provided for. You could create more input variables as per your convenience.

class AddGroundTemperatures < OpenStudio::Measure::ModelMeasure

  #define the name that a user will see
  def name
    return "Add user defined monthly Ground Temperatures"
  end

  # human readable description
  def description
    return 'Set the ground temperature to user-defined values for all months'
  end

  # human readable description of modeling approach
  def modeler_description
    return 'Adds a specific ground temperature overriding the default energyplus ground temperature of 18 degree celsius.'
  end

  #define the arguments that the user will input
  def arguments(model)

    args = OpenStudio::Measure::OSArgumentVector.new

    # Define input variables
    ground_temp = OpenStudio::Measure::OSArgument::makeDoubleArgument('ground_temp',true)
    ground_temp.setDisplayName('Ground Temperature')
    ground_temp.setDefaultValue(18)
    args << ground_temp

    return args
  end #end the arguments method


  #define what happens when the measure is run
  def run(model, runner, user_arguments)
    super(model, runner, user_arguments)

    #use the built-in error checking
    if not runner.validateUserArguments(arguments(model), user_arguments)
      return false
    end

    #set user defined values to variables
    ground_temp = runner.getDoubleArgumentValue('ground_temp',user_arguments)

    # assign the user inputs to variables
    data=[ground_temp,ground_temp,ground_temp,ground_temp,ground_temp,ground_temp,ground_temp,ground_temp,ground_temp,ground_temp,ground_temp,ground_temp]
    # create ground temperature object    
    groundtemps = OpenStudio::Model::SiteGroundTemperatureBuildingSurface.new(model)
    # add monthly temperatures
    groundtemps.setAllMonthlyTemperatures(data)


    # check the ground temperature for reasonableness
    if ground_temp <=0
      runner.registerError("Please choose a temperature above 0")
      return false
    end


    # report final condition
    runner.registerFinalCondition("The model's ground temperature was changed to #{ground_temp}.")


    return true

  end #end the run method

end #end the measure

#this allows the measure to be used by the application
AddGroundTemperatures.new.registerWithApplication