This data is available in v6.2 and later.
Kiva foundation objects describe boundary conditions for ground-coupled foundation surfaces when one of the Kiva Ground modelling methods have been selected (2-Kiva Basic or 4-Kiva Full).
The inputs from Kiva foundation objects are translated into Kiva’s foundation heat transfer model. Kiva generates a two-dimensional heat transfer calculation to represent heat flow between a zone and the adjacent ground. Kiva foundation surfaces do not use the same Solution Algorithm (e.g. CTF, Finite difference etc) as the rest of the model.
Kiva foundation objects are used to describe the two-dimensional features that cannot be captured by the typical one-dimensional constructions used in EnergyPlus. The figure below illustrates Kiva’s two-dimensional context for a basement where the basement slab and wall both refer to “Foundation” as the Outside Boundary Condition, the ceiling of the basement and the exterior wall of the zone above the basement refer to “Surface” (or “Zone”) and “Outdoors”, respectively.
Note: Not all of the foundation wall surface needs to be below grade (see the Wall height above grade field below). Any part above grade is modelled in Kiva’s two-dimensional heat transfer calculations. The non-foundation surfaces are shown in the figure below for context, but are not part of the Kiva model.
Outside Boundary Conditions for surfaces within Kiva’s Two-dimensional context. Only surfaces referencing Foundation are simulated in Kiva
This context allows for a finer description of the structural and insulation components of a foundation that impact heat transfer (see figure below).
Structural and insulation components of Foundation:Kiva objects
Kiva foundation objects define only the aspects of the foundation that are not already defined by the one-dimensional constructions of the respective surfaces. That is, the footing wall and slab constructions and their relative dimensions are inferred from the respective Surface objects (see figure below).
Two-dimensional interpretation of foundation surface data
The depth of the foundation is defined by the height of the wall surfaces that reference the Kiva foundation boundary condition object. For slab-on-grade foundations, a depth of zero is implied by having no associated wall surfaces. The figure below shows a slab-on-grade foundation with whole slab insulation. Notice there are no walls referencing the “Foundation” Outside Boundary Condition. In this case, the under-slab insulation is modelled as part of the slab construction, while the edge/gap insulation is modelled using the interior vertical insulation fields of a Kiva foundation object.
Note: Since there are no wall surfaces for slab foundations, the footing wall construction is defined within the Kiva foundation object.
Two-dimensional interpretation of foundation surface data
A walkout basement (with a variable grade along the sides; see figure below) must be modelled using discrete quadrilateral surfaces of stepped height for the walls.
Example walkout basement
Walkout basement wall and floor surfaces (in grey) all reference the same Kiva foundation object
The width of the floor surface in the two-dimensional context is defined by the area and the exposed perimeter of the floor surface object. Details on this calculation can be found in the Engineering Reference document.
Other components of the two-dimensional context are defined by the Kiva foundation settings object and applied uniformly for all Kiva foundation objects. These components include:
Limitations when using Kiva foundation objects include:
The unique identifier of the Kiva foundation object.
Check this checkbox if interior horizontal insulation is to be included with this Kiva foundation object.
Interior horizontal insulation material
Select the material associated with the interior horizontal insulation.
The following two fields define the placement of this material within Kiva’s two-dimensional context as illustrated in the figure below.
Placement of interior horizontal insulation
Width
Extent of insulation as measured from the wall interior to the edge of interior horizontal insulation (in m or ft).
Depth
Distance from the wall top to the top of interior horizontal insulation (in m or ft).
Check this checkbox if interior vertical insulation is to be included with this Kiva foundation object.
Material
Select the material object associated with the interior vertical insulation.
The following field defines the placement of this material within Kiva’s two-dimensional context as illustrated in the figure below.
Placement of interior vertical insulation
Depth
Extent of insulation as measured from the wall top to the bottom edge of the interior vertical insulation (in m or ft).
Check this checkbox if exterior horizontal insulation is to be included with this Kiva foundation object.
Material
Select the material associated with the exterior horizontal insulation.
The following two fields define the placement of this material within Kiva’s two-dimensional context as illustrated in the figure below.
Placement of exterior horizontal insulation
Width
Extent of insulation as measured from the wall exterior to the edge of exterior horizontal insulation (in m or ft).
Depth
Distance from the wall top to the top of exterior horizontal insulation (in m or ft).
Check this checkbox if exterior vertical insulation is to be included with this Kiva foundation object.
Material
Select the material associated with the exterior vertical insulation.
The following field defines the placement of this material within Kiva’s two-dimensional context as illustrated in the figure below.
Placement of exterior vertical insulation
Depth
Extent of insulation as measured from the wall top to the bottom edge of the exterior vertical insulation (in m or ft).
Distance from the exterior grade to the wall top (in m or ft).
The figure below illustrates the definition of both the Wall height above grade and the following field, Wall depth below slab.
Definition of exterior grade and footing wall depth relative to the wall surface
Distance from the slab bottom to the bottom of the foundation wall (in m or ft).
Extending the wall below the slab provides a coarse approximation of the foundation footing. Alternatively, one may use the the fields “Footing Material Name” and “Footing Depth” to explicitly model the footing.
Note: Explicit modelling of the footing requires a higher spatial discretization and, therefore, longer computation times.
Defines the construction of the foundation footing wall for slab foundations where the foundation wall is not exposed to the zone (and has no zone surface to explicitly assign a construction).
By default, this is the same construction as any associated below-grade wall surfaces, or a 0.3 m wide poured concrete wall (conductivity = 1.95 W/m-K, density = 2,240 kg/m3, specific heat = 900 J/kg-K).
If a foundation footing is to be included then check this checkbox to reveal the further associated settings described below.
Footing material
Select the material associated with the foundation footing (typically some form of concrete).
The following field defines the placement of this material within Kiva’s two-dimensional context and are illustrated in the figure below.
Placement of footing
Footing width
Horizontal width dimension of the footing (in or ft).
Footing depth
Top-to-bottom dimension of the footing (not to be confused with its depth in the ground) (in m or ft).
Custom blocks can be used to represent solid materials in the two-dimensional context that are not otherwise covered by the fields above. Examples of this might include interior finishings and insulation or backfill soil with different thermal properties (see figures below).
Custom blocks representing interior batt insulation and dry wall
Custom block representing exterior backfill
If custom blocks are to be associated with this Kiva foundation object then select the number of them here. Any value from 0 to 10 is allowed.
Select the material associated with a custom block in the two-dimensional foundation context.
If two or more custom blocks overlap, the final properties are determined by the higher block number (e.g., Custom Block 4 in the input object supersedes properties defined by Custom Block 2). All custom blocks properties are superseded by the elements shown in the figure below.
The following fields defines the placement of this material within Kiva’s two-dimensional context and are illustrated in the Figure below.
Placement of a custom block
Horizontal width of the custom block (in m or ft).
Top-to-bottom dimension of the block downward (in m or ft). The default is the depth from the wall top to the top of the slab to facilitate interior constructions.
Position outward (+) or inward (-) relative to the foundation wall (in m or ft).
Position downward (+) relative to the foundation wall top (in m or ft).
