One can learn the basics of heat transfer, R values, U values, and all that stuff reasonably quickly and the physics and and fundamentals apply in every house. But the mechanical equipment can be a nightmare of pipes and pumps and wires and fans, and the variations seem to go on forever. I have found that the "Fundamentals of HVACR" from Pearson publishers is a good all around informational resource. But there seem to be a bunch of others that focus on specific types of equipment. It would be interesting to hear other people's recommendations on books that can us do this part of the analysis better.