# Walls¶

## Wall Orientation¶

The flexibility of HPXML allows specification of any number of walls and windows facing any direction. HEScore expects only one wall/window specification for each side of the building (front, back, left, right).

Each wall in the HPXML document that has an ExteriorAdjacentTo='ambient' (HPXML v2) or ExteriorAdjacentTo='outside' (HPXML v3) or is missing the ExteriorAdjacentTo subelement (assumed to be ambient/outside) is considered for translation to HEScore. This excludes attic knee walls (see Knee Walls), interior walls, walls between living space and a garage, etc. since HEScore does not model those walls. The translator then attempts to assign each wall to the nearest side of the building, which is relative to the orientation of the front of the building. The wall construction and exterior finish of the largest wall by area on each side of the building are used to define the properties sent to HEScore. An area weighted R-value of all the walls on each side of the building is calculated as well as described in Area Weighted Wall R-value. If there is only one wall on any side of the house, the area is not required for that side. If a wall falls exactly between two sides of the house the area of the wall is divided by two and half of the wall is assigned to either side.

HEScore also allows the specification of one wall for all sides of the building. If none of the walls in HPXML have orientation (or azimuth) data, the wall construction and exterior finish of the largest wall by area on each side of the building are used to define the properties sent to HEScore. An area weighted R-value of all the walls on each side of the building is calculated as well as described in Area Weighted Wall R-value. If there is only one wall and no area specified, that wall is used to determine the wall construction.

Note

The following conditions must be met for the wall translation to succeed:

• If there is more than one wall on each side of the building each wall on that side of the building must have an Area specified.
• Either all walls must have an Azimuth and/or Orientation or none of them must.

## Wall Construction¶

HEScore uses a selection of construction codes to describe wall construction type, insulation levels, and siding. HPXML, as usual, uses a more flexible approach defining wall types: layers of insulation materials that each include an R-value, thickness, wall cavity information, etc. To translate the inputs from HPXML to HEScore approximations need to be made to condense the continuous inputs in HPXML to discrete inputs required for HEScore.

### Wood Frame Walls¶

If WallType/WoodStud is selected in HPXML, each layer of the wall insulation is parsed and if a rigid and continuous layer is found, or if the subelement WallType/WoodStud/ExpandedPolyStyreneSheathing is found, the wall is specified in HEScore as “Wood Frame with Rigid Foam Sheathing.”

<Wall>
<SystemIdentifier id="wall1"/>
<WallType>
<WoodStud>
<!-- Either this element needs to be here or continuous insulation below -->
<ExpandedPolystyreneSheathing>true</ExpandedPolystyreneSheathing>
</WoodStud>
</WallType>
<Insulation>
<SystemIdentifier id="wall1ins"/>
<Layer>
<InstallationType>continuous</InstallationType>
<InsulationMaterial>
<Rigid>eps</Rigid>
<!-- This can have any of the valid enumerations for this element,
it only cares if the Rigid element is present. -->
</InsulationMaterial>
<NominalRValue>5</NominalRValue>
</Layer>
...
</Insulation>
</Wall>


Otherwise, if the OptimumValueEngineering boolean element is set to true, the “Wood Frame with Optimal Value Engineering” wall type in HEScore is selected.

<Wall>
<SystemIdentifier id="wall2"/>
<WallType>
<WoodStud>
<OptimumValueEngineering>true</OptimumValueEngineering>
</WoodStud>
<Insulation>
...
</Insulation>
</WallType>
</Wall>


Note

The OptimumValueEngineering flag needs to be set in HPXML to translate to this wall type. The translator will not infer this from stud spacing.

Finally, if neither of the above conditions are met, the wall is specified as simply “Wood Frame” in HEScore.

In all cases the R-value is summed for all insulation layers and the nearest discrete R-value from the list of possible R-values for that wall type is used. For walls with rigid foam sheathing, R-5 is subtracted from the nominal R-value sum to account for the R-value of the sheathing in the HEScore construction assembly.

Siding is selected according to the siding map.

### Structural Brick¶

If WallType/StructuralBrick is found in HPXML, one of the structural brick codes in HEScore is specified. The nearest R-value to the sum of all the insulation layer nominal R-values is selected.

<Wall>
<SystemIdentifier id="wall3"/>
<WallType>
<StructuralBrick/>
</WallType>
<Insulation>
<SystemIdentifier id="wall3ins"/>
<Layer>
<NominalRValue>5</NominalRValue>
</Layer>
<Layer>
<NominalRValue>5</NominalRValue>
</Layer>
<!-- This would have a summed R-value of 10 -->
</Insulation>
</Wall>


### Concrete Block or Stone¶

If WallType/ConcreteMasonryUnit or WallType/Stone is found, one of the concrete block construction codes is used in HEScore. The nearest R-value to the sum of all the insulation layer nominal R-values is selected. The siding is translated using the same assumptions as wood stud walls with the exception that vinyl, wood, or aluminum siding is not available and if those are specified in the HPXML an error will result.

### Straw Bale¶

If WallType/StrawBale is found in the HPXML wall, the straw bale wall assembly code in HEScore is selected.

### Exterior Finish¶

Siding mapping is done from the Wall/Siding element in HPXML. Siding is specified as the last two characters of the construction code in HEScore.

Siding type mapping
HPXML HEScore
wood siding wo
stucco st
synthetic stucco st
vinyl siding vi
aluminum siding al
brick veneer br
asbestos siding wo
fiber cement siding wo
composite shingle siding wo
masonite siding wo
other not translated

Note

not translated means the translation will fail for that house.

## Area Weighted Wall R-value¶

When more than one HPXML Wall element must be combined into one wall construction for HEScore, the wall construction code is determined for each HPXMl Wall as described in Wall Construction. The wall construction and exterior finish that represent the largest combined area are used to represent the side of the house.

A weighted R-value is calculated by looking up the center-of-cavity R-value for the wall construction, exterior finish, and nominal R-value for each Wall from the following table.

Wall center-of-cavity R-values
Exterior Wood Siding Stucco Vinyl Aluminum Brick Veneer None
R-value Effective R-value
Wood Frame
R-0 3.6 2.3 2.2 2.1 2.9
R-3 5.7 4.4 4.3 4.2 5.0
R-7 9.7 8.4 8.3 8.2 9.0
R-11 13.7 12.4 12.3 12.2 13.0
R-13 15.7 14.4 14.3 14.2 15.0
R-15 17.7 16.4 16.3 16.2 17.0
R-19 21.7 20.4 20.3 20.2 21.0
R-21 23.7 22.4 22.3 22.2 23.0
Wood Frame w/insulated sheathing
R-0 6.1 5.4 5.3 5.2 6.0
R-3 9.1 8.4 8.3 8.2 9.0
R-7 13.1 12.4 12.3 12.2 13.0
R-11 17.1 16.4 16.3 16.2 17.0
R-13 19.1 18.4 18.3 18.2 19.0
R-15 21.1 20.4 20.3 20.2 21.0
R-19 25.1 24.4 24.3 24.2 25.0
R-21 27.1 26.4 26.3 26.2 27.0
Optimum Value Engineering
R-19 21.0 20.3 20.1 20.1 20.9
R-21 23.0 22.3 22.1 22.1 22.9
R-27 29.0 28.3 28.1 28.1 28.9
R-33 35.0 34.3 34.1 34.1 34.9
R-38 40.0 39.3 39.1 39.1 39.9
Structural Brick
R-0           2.9
R-5           7.9
R-10           12.8
Concrete Block
R-0   4.1     5.6 4.0
R-3   5.7     7.2 5.6
R-6   8.5     10.0 8.3
Straw Bale
R-0   58.8

Then a weighted average is calculated by weighting the U-values values by area.

\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 R-0 center-of-cavity R-value ($$R_{offset}$$) is selected for the highest weighted wall construction type represented in the calculation and is subtracted from $$R_{eff,avg}$$. For construction types where there is no R-0 nominal value, the lowest nominal R-value is subtracted from the corresponding effective R-value.

$R = R_{eff,avg} - R_{offset}$

Finally the R-value is rounded to the nearest insulation level in the enumeration choices for the highest weighted roof construction type included in the calculation.