The Kusuda equation is described in one of the theses available for download
on the SEL website:
We've already taken the algorithm and programmed it into a TRNSYS
type. It's available through the TESS component libraries for TRNSYS if
you are interested. We also have 3-D models for the soil surrounding a
basement and a slab floor that uses the Kusuda correlation as a starting
point for the calculations. These models will be made available in Version
2 of our libraries - to be released for Version 16 of TRNSYS scheduled for
Early 2004.