Virtual simulation of passenger compartment climatic conditions is becoming increasingly important as a complement to the wind tunnel and field testing to achieve improved thermal comfort while reducing the vehicle development time and cost. The vehicle cabin is subjected to various thermal environments. At the same time many of the design parameters are dependent on each other and the relationship among them is quite complex. Therefore, an experimental parametric study is very time consuming. The present 3-D RadTherm analysis coupled with the 3-D CFD flow field analysis takes into account the geometrical configuration of the passenger compartment which includes glazing surfaces and pertinent physical and thermal properties of the enclosure with particular emphasis on the glass properties. Virtual Thermal Comfort Engineering (VTCE) is a process that takes into account the cabin thermal environment coupled with a human physiology model. This model uses multiple body segments and each segment is modeled as several body layers (core, muscle, fat, and skin tissues) and a clothing layer. The UC Berkeley comfort model has the ability to predict local and overall thermal comfort levels of an occupant based on local skin and core temperatures and their time rate of changes. The combination of the present thermal analysis and the thermal comfort evaluations based on the human physiology model will shed light on the climate control strategies as they relate to the occupant thermal comfort for an “Energy Efficient HVAC System”.