Solid Hardwood, Engineered and Laminate Flooring - old heart pine floor

I have old heart pine floors in an 1800 sq. ft. pier and beam house I am remodeling. The house was built about 85 years ago, and the floor is constructed with no subfloor. I live in southeast Texas where heat and humidity can be stifling, so I installed central air and heat. I plan to refinish the floors but need information regarding the proper finish to use. Should I use a finish that breathes or use a sealing finish? Would insulating the floors between floor joists help to preserve the old floors and give me more choices of finish products to use?

We have heartpine floors in our 100 year old house. Some of the floors were polyurethaned by a previous owner and they have held up beautifully during the 14 years we have lived here. Some of the floors were just plain, unfinished wood. I have taken care of them by applying a good floor paste wax and buffing with a machine using the bristle pads rather than the buffing pads as the buffing pads seem to snag on the floor. I don't know about insulating under your floors. It would certainly help maintain the inside temp. of your home. We have not done so and in the winter, we do notice that the boards shrink a tiny amount and allow a small draft. I use area rugs throughout the house so the draft problem isn't too bad. A poly finish will be more durable than just paste wax and is easier to take care of, but I like the look of floors just finished with paste wax, so it is really a personal preference and how much maintenance you are willing to do. The paste wax finish does need to be redone once or twice a year whereas the poly finish only requires damp mopping. Hope this is helpful!