Kiva Limitations

Some limitations in the current implementation of Kiva are: 

1. Only floors and walls can connect to the ground through Kiva foundation boundary conditions.

2. At least one-floor surface must reference each Kiva foundation object.

3. To model two stories at -1 and -2 levels using Kiva requires a workaround since when using Kiva for a zone in EnergyPlus, that zone must have one-floor surface touching the ground for Kiva to calculate heat transfer. There are two ways to do this:
   1. Keep the zones stacked, but use Kiva for only the -2 level zone and change the boundary condition for the walls of the -1 level zone to use standard ground modelling, i.e. uncheck the Kiva adjacency checkbox for these wall surfaces. This is necessary because a Kiva wall from the upper zone can’t be connected to the floor of the zone below and Kiva walls must be connected to a Kiva floor.
   2. Merge the two zones together to remove the ceiling for the -2 level zone and floor for the -1 level zone and modelling that surface as Internal Thermal Mass instead.

The second option would generally be the easiest and most accurate choice.

4. Kiva ground modelling is not compatible with Fanger PMV temperature control in E+ v9.4. The bug is fixed in E+ v9.6 and later.

5. Outputs for surfaces with a Foundation boundary condition type will include all opaque surface output variables except: 
   • Surface Outside Face variables (since there is no “Outside Face”).
   • Surface Heat Storage variables (since this definition depends on an “Outside Face”).
   • Surface Internal Source Location Temperature (Kiva doesn’t handle internal sources yet, but this is a possible future enhancement).

6. Kiva is not compatible with F-Factor constructions used in Kiva ground adjacent surfaces. This means that you should not use Kiva for LEED and ASHRAE 90.1 Appendix G simulations.

7. Kiva is not compatible with constructions with Simple resistance (R-value) material layers in Kiva ground adjacent surfaces.

8. Kiva is not compatible with constructions with an internal source (e.g. underfloor heating) used in Kiva ground adjacent surfaces. You can use surfaces with an internal source in any other surface in Kiva simulations though. See EnergyPlus issue #6576.
9. The Kiva ground domain is not used by Detailed HVAC Ground heat exchangers which have their own representation of the ground temperature field, typically based on G-function data for vertical ground heat exchangers.