# Foundation Insulation¶

## Determining the primary foundation¶

HEScore permits the specification of two foundations. The two foundations that cover the largest area are selected. This is determined by summing up the area of the FrameFloor 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.

HPXML to HEScore foundation type mapping
HPXML Foundation Type HEScore Foundation Type
Basement Conditioned=”true” cond_basement
Conditioned=”false” or omitted uncond_basement
Crawlspace Vented=”true” vented_crawl
Vented=”false” or omitted unvented_crawl
Garage unvented_crawl
AboveApartment not translated
Combination not translated
Ambient vented_crawl
RubbleStone not translated
Other not translated

Warning

For foundation types that are not translated the translation will return an error.

## Foundation wall insulation R-value¶

If the foundation type is a basement or crawlspace, 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 R-value is the sum of the FoundationWall/Insulation/Layer/NominalRValue element values for each foundation wall. For each foundation wall, an effective R-value is looked up based on the nearest R-value in the following table.

Basement and crawlspace wall effective R-values
Insulation Level Effective R-value
R-0 4
R-11 11.6
R-19 16.9

Then a weighted average R-value is calculated by weighting the U-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 effective R-value of the R-0 insulation level is then subtracted.

$R = R_{eff,avg} - 4.0$

Finally, the nearest insulation level is selected from the enumeration list.

## 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.

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.

\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.

$R = R_{eff,avg} - 4.0$

Finally, the nearest insulation level is selected from the enumeration list.

## Floor insulation above basement or crawlspace¶

If the foundation type is a basement or crawlspace, for each frame 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 R-value is the sum of the FrameFloor/Insulation/Layer/NominalRValue element values for each frame floor. The effective R-value is looked up in the following table.

Floor center-of-cavity effective R-value
Insulation Level Effective R-value
R-0 4
R-11 15.8
R-13 17.8
R-15 19.8
R-19 23.8
R-21 25.8
R-25 31.8
R-30 37.8
R-38 42.8

Then a weighted average R-value is calculated by weighting the U-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 effective R-value of the R-0 insulation level is then subtracted.

$R = R_{eff,avg} - 4.0$

Finally, the nearest insulation level is selected from the enumeration list.