Modeling Foundation Walls

This article explains how to model foundation walls for complex insulation configurations. Keep in mind that foundation wall modeling is only required when the enclosed space is a conditioned basement or crawl space. 

Foundation walls should be modeled separately if the geometry in the main input field varies. For example, two walls with different depth below grade or height above grade should be modeled separately, or if two walls have different insulation configurations. Please refer to the Envelope Help article for more information.

However, we are aware that in some cases there are foundation walls where the insulation is not the same across the entire surface. In the cases where the insulation does not extend the full height of the foundation wall, you can uncheck the box Fully insulated (top to bottom) and use the input fields Feet from top of wall to top of insulation and Feet from top of wall to bottom of insulation to define the total insulation depth.

Note that for projects from version 4.2.0, the algorithm assumes that the foundation wall insulation always starts at the top of the wall. If you enter a value greater than 0 in Feet from top of wall to top of insulation, the algorithm calculates the total insulation depth as the Feet from top of wall to bottom of insulation minus Feet from top of wall to top of insulation. If the insulation is located other than at the top of the foundation wall, please do not model the wall piece by piece. Version 4.2.0 does not support modeling foundation walls on top of each other. In this case, our suggestion as follows:

1. For continuous wall insulation, map the different wall surfaces and their corresponding continuous insulation R-values (use R = 0 for uninsulated wall sections). 
2. Calculate the surface-weighted average of the wall U-value as follows

       3. In the R-value field for continuous insulation, use 1 / Ueq as the value. Check the wall to be fully insulated.

       4.  Repeat the same for the cavity insulation and enter the result in the R-value field for the stud/cavity layer.