When the Ground modelling method has been set to 2-Kiva Basic or 4-Kiva Full, the Kiva foundation settings component selected at site level defines the soil thermal and surface properties, the extent of the domain and some calculation options that are to be applied across all Kiva foundation calculations. Just one Kiva foundation settings object is required for a simulation.
Enter a unique name for this Kiva foundation settings component.
The thermal conductivity of the soil (in W/m-K or Btu-in/h-ft2-°F).
The bulk density of the soil (in kg/m3 or lb/ft3).
The specific heat of the soil (in J/kg-K or Btu/lb-°F).
Enter the properties of the ground surface.
Solar absorptivity of the exterior grade surface.
Long-wave absorptivity (emissivity) of the exterior grade surface.
The relief roughness of the exterior ground surface in m. Some typical surface roughness for various surface types are shown in the Table below.
| Example Surface | Roughness [m] |
|---|---|
| Concrete | 0.002 |
| Brick | 0.003 |
| Soil | 0.005 |
| Gravel | 0.012 |
| Grass | 0.030 |
The distance from the wall interior to the zero horizontal heat flux (i.e., adiabatic) far-field boundary (in m or ft). This distance represents either the distance halfway between this foundation and a similar foundation of a neighbouring building, or a distance adequately far from the foundation such that it is isolated from the effects of the boundary (typically >= 40 m).
The distance from the exterior grade to the deep ground boundary (in m or ft). This distance represents either the distance to the ground water level, or a distance adequately far from the foundation such that it is isolated from the effects of the boundary (typically >= 40 m).
If you know the water table depth, then it is generally more accurate to model the boundary at that depth using the water table temperature.
The recommended setting for Deep-ground depth is 40m.
The Deep-ground depth setting can be set to Autocalculate in which case Kiva will use a correlation to estimate how deep the ground water is based on the elevation of your location. If you use this option you should be aware that ground heat transfer can be very sensitive to the location of the water table which is much more geospatially variable than the correlation represents (e.g. elevation and water table depth at your weather station could be very different from your actual building site).
The minimum cell dimension (in m or ft) used in the Kiva discretisation. Default: 0.02 m.
The maximum ratio of growth between neighbouring cells in the direction away from the near-field area of interest. Default: 1.50.
This field allows the user to choose whether to calculate foundation loads on the zone timestep or at hourly intervals. Hourly intervals will allow for less overall computation time, but with less accuracy. Choices are:
Defines the type of boundary condition to apply at the Deep-ground depth. Options are:
Williams and Williamson, 1989 provide this simple correlation to help estimate the depth of the water table, dwt from the site elevation above sea level, delev:
If dwt <= 40 m., the 3-Ground water boundary is applied, otherwise a 2-Zero flux boundary is applied at 40 m. If the calculated ground water depth is shallower than any element of the foundation construction, then the 3-Ground water option is applied at 1m below the lowest element. The default is 1-Autoselect.