In the field of HVAC systems, it depends on what you are looking to do and how much schooling and training you are interested in undergoing. Often tech schools and community colleges have programs (make sure it is an accredited program) that are only about a year long and you will walk out with certification that can place you in a service/installation technician position. It also might depend on if you plan on going into industrial or residential and commercial installation and service in the HVAC field. Many of the systems in the market today are fully automated and run off of sensor arrays and programmable logic controllers (PLC's for short) that allow the clients to set parameters for the functionality of the system. For many of the areas involved in HVAC beyond service and installation technician, you would want to explore the possibility of an Associates of Science degree (AS) in Mechanical Engineering, Electrical Engineering, or Electro-Mechanical Engineering, or an Associates of Applied Science degree (AAS) in Mechanical Engineering Technology, Electrical Engineering Technology, or Electro-Mechanical Technology. Associates degree programs are usually about 2 years long. Again most community colleges and tech schools have a curriculum designed to prepare you for the workforce and therefore will have a program geared towards HVAC systems. There are several scientific and technical courses of study in the engineering disciplines that have an application to HVAC systems, the big ones being physics, fluid mechanics / hydraulics, and pneumatics, and Thermodynamics. You stated that you are currently enlisted in the reserves. Thank you for you service. I am a Marine Corps veteran and as such was able to use my GI Bill Benefits to pay for school. If you are interested in any field of study, there are education benefits available to you and you can explore those benefits either by lobbying your chain of command or by contacting any number of veterans service organizations. Most colleges and tech schools have veterans and military service offices on campus. If there are any further questions I might be able to answer for you or help you with, please don't hesitate to ask. I hope this helped a bit. Good luck.