Foundation Insulation ##################### Determining the primary foundation ********************************** HEScore permits the specification of two foundations. A ``Foundation`` element for each foundation in the house is required in HPXML. The two foundations that cover the largest area are selected. This is determined by summing up the area of the ``FrameFloor`` (v2 or v3), ``Floor`` (v4), or ``Slab`` elements (depending on what kind of foundation it is). ``Area`` elements are required for all foundations unless there is only one foundation, then it is assumed to be the footprint area of the building. If there are more than two foundations, the areas of the largest two are scaled up to encompass the area of the remaining foundations while maintaining their respective area fractions relative to each other. Foundation Type *************** Once a foundation is selected, the HEScore foundation type is selected from HPXML according to the following table. .. table:: HPXML to HEScore foundation type mapping +----------------------+-------------------+-------------------------+ |HPXML Foundation Type | HEScore Foundation Type | +======================+===================+=========================+ |Basement |Conditioned="true" |cond_basement | + +-------------------+-------------------------+ | |Conditioned="false"|uncond_basement | | |or omitted | | +----------------------+-------------------+-------------------------+ |Crawlspace |Vented="true" |vented_crawl | + +-------------------+-------------------------+ | |Vented="false" |unvented_crawl | | |or omitted | | +----------------------+-------------------+-------------------------+ |SlabOnGrade |slab_on_grade | +----------------------+-------------------+-------------------------+ |Garage |unvented_crawl | +----------------------+-------------------+-------------------------+ |AboveApartment |above_other_unit | +----------------------+-------------------+-------------------------+ |Combination |*not translated* | +----------------------+-------------------+-------------------------+ |Ambient |vented_crawl | +----------------------+-------------------+-------------------------+ |RubbleStone |*not translated* | +----------------------+-------------------+-------------------------+ |BellyAndWing [#f1]_ |belly_and_wing | +----------------------+-------------------+-------------------------+ |Other |*not translated* | +----------------------+-------------------+-------------------------+ .. [#f1] BellyAndWing is first available in HPXML v4. It can be specified in earlier versions using ``FoundationType/Other/extension/BellyAndWing`` element. .. warning:: For foundation types that are *not translated* the translation will return an error. .. _foundation_wall-insulation: Foundation wall insulation R-value ********************************** If the foundation type is a basement or crawlspace, a ``FoundationWall`` is required to be referenced via the ``Foundation/AttachedtoFoundationWall`` element. For each foundation wall R-value can be described by using nominal R-value or assembly R-value. If a user wishes to use a nominal R-value, nominal R-value for all layers need to be provided. Otherwise, assembly R-values for the whole foundation wall needs to be provided. Preference is given to assembly R-values. If nominal R-value is specified, the R-value is the sum of the ``FoundationWall/Insulation/Layer/NominalRValue`` element values for each foundation wall. For each foundation wall, an assembly R-value for that wall is looked up based on the nearest R-value in the following table. .. _basement_crawlspace_wall_eff_rvalues: .. table:: Basement and crawlspace wall effective R-values ================= ================== Insulation Level Effective R-value ================= ================== R-0 4 R-11 11.6 R-19 16.9 ================= ================== When more than one HPXML ``FoundationWall`` element must be combined into one foundation wall construction for HEScore, an area weighted average R-value is calculated for the foundation walls. The area is obtained from the ``Area`` element, if present, or calculated from the ``Length`` and ``Height`` elements. The weighted average R-value is calculated by weighting the U-values by area. .. math:: :nowrap: \begin{align*} U_i &= \frac{1}{R_{eff,i}} \\ U_{avg} &= \frac{\sum_i{U_i A_i}}{\sum_i A_i} \\ R_{eff,avg} &= \frac{1}{U_{avg}} \\ \end{align*} Finally, the nearest nominal insulation level is selected from :ref:`basement_crawlspace_wall_eff_rvalues`. Slab insulation R-value *********************** If the foundation type is a slab on grade, an area weighted average R-value is calculated using the value of ``ExposedPerimeter`` as the area. (The units work out, the depth in the area drops out of the equation.) The R-value is the sum of the ``Slab/PerimeterInsulation/Layer/NominalRValue`` element values for each foundation wall. For each slab, an effective R-value is looked up based on the nearest R-value in the following table. .. table:: Slab insulation effective R-values ================= ================== Insulation Level Effective R-value ================= ================== R-0 4 R-5 7.9 ================= ================== Then a weighted average R-value is calculated by weighting the U-values by area. .. math:: :nowrap: \begin{align*} U_i &= \frac{1}{R_i} \\ U_{eff,avg} &= \frac{\sum_i{U_i A_i}}{\sum_i A_i} \\ R_{eff,avg} &= \frac{1}{U_{eff,avg}} \\ \end{align*} The effective R-value of the R-0 insulation level is then subtracted. .. math:: R = R_{eff,avg} - 4.0 Finally, the nearest insulation level is selected from the enumeration list. .. _floor-insulation: Floor insulation above basement, crawlspace, or belly and wing ************************************************************** .. warning:: In HPXML v2 and v3, the ``FrameFloor`` element is used to describe the floor. In HPXML v4, the ``Floor`` element is used. The translation logic is the same between versions of HPXML, in the documentation we will use ``Floor``, but if you are using HPXML v2 or v3, you should replace with ``FrameFloor``. If the foundation type is an unconditioned basement, crawlspace, or manufactured home belly and wing, a ``Floor`` element is required to be referenced via the ``Foundation/AttachedToFloor`` element. For each floor above the foundation, a weighted average using the floor area and R-value are calculated. The area is obtained from the ``Area`` element. The floor R-value can be described by using ``NominalRValue`` or ``AssemblyEffectiveRValue``. If a user wishes to use a nominal R-value, ``NominalRValue`` elements for all layers need to be provided. Otherwise, ``AssemblyEffectiveRValue`` element is required. Nominal R-value --------------- If ``NominalRValue`` is used, the nominal R-value of each layer is summed for the floor: ``sum(Floor/Insulation/Layer/NominalRValue)``. The nearest assembly code to that nominal R-value is selected from the :ref:`lookup table `. For example, the following ``Floor`` in xml: .. code-block:: xml 10 8 Has a summed nominal R-value of 18, which corresponds to the closest assembly code ``efwf19ca`` and an assembly effective R-value of 22.2. Assembly Effective R-value -------------------------- If ``AssemblyEffectiveRValue`` is used, the nominal R-value nearest to assembly effective R-value from the :ref:`lookup table ` is used. Combining Multiple Floors ------------------------- When more than one HPXML ``Floor`` element must be combined into one floor construction for HEScore, a weighted average assembly R-value is determined by weighting the U-values by area. .. math:: :nowrap: \begin{align*} U_i &= \frac{1}{R_{eff,i}} \\ U_{eff,avg} &= \frac{\sum_i{U_i A_i}}{\sum_i A_i} \\ R_{eff,avg} &= \frac{1}{U_{eff,avg}} \\ \end{align*} Then the assembly code nearest to the weighted average assembly R-value from the :ref:`lookup table ` is selected. .. _floor_eff_rvalue_tbl: .. csv-table:: Lookup table for floor effective R-values :file: ../../../hescore-hpxml/hescorehpxml/lookups/lu_floor_eff_rvalue.csv Manufactured home belly and wing assemblies ------------------------------------------- .. todo:: This should be moved to an engineering documentation section. For the assembly R-value and U-value of the belly and wing foundation, we made assumptions as follows: * All floor joists are 2x6 16 inches o.c. * In the outer portion of the floor, the loose insulation is compressed against the frame. So, there is no air space between the frame and loose insulation. * 10% frame fraction and 10% outer portion of the floor. * The subfloor is 5/8” plywood. * The interior floor covering is R-2 carpet. * To determine the assembly R-value, the floor is divided into four heat transfer paths: * Framing area on the outer portion where the loose insulation is compressed against the frame. * Framing area in the center where the insulation is not compressed. * Non-framing area on the outer portion where the loose insulation is compressed against the frame. * Non-framing area in the center where the insulation is not compressed. * A rectangular belly with a depth of 14 inches because the duct diameter for a manufactured home is commonly limited to 14 inches. * The loose insulation has larger area compared to the floor area, but when modeling the floor, it is necessary to model it using the floor area. Therefore, the R-value of the loose insulation is modified based on the ratio of the loose insulation area to the floor area, with an assumed ratio of 1.04.