Dr. Spitler has worked in the ground source heat pump area for 14 years.  His first research involved the development of a ground loop heat exchanger design tool that was suitable for any size commercial building, and which automated many of the calculations and iterations that would have been required previously.  This design tool is widely used in North America, Asia and Europe.  Development and use of this design tool revealed areas where additional research was needed.  This additional research included development of test apparatus and analysis procedures for determination, in situ of thermal conductivity of soil and rock surrounding a test borehole.  Based on this work and subsequent refinements, there are now a number of companies that offer this testing throughout North America.  Spitler developed the first energy calculation models for ground source heat pump systems that have now been incorporated into the most widely used energy calculation programs.