Awesome explanation! When I say heat pump to people, it's amazing how often their eyes glaze over...even though most of them have had refrigerators and air-conditioners their whole lives and have never asked themselves how they work. Same principle! Compressor and expansion valve (and the heat-holding capacity of a phase change; another confusing one for people). thanks for helping educate!
Eliminate any problem spots to make the subfloor level. Sand minor humps down with a hand-held or orbital sander to make the subfloor level. To fill any dips or low spots, use a leveling compound (also known as floor patch). Mix up the compound according to package directions, fill in the dips, then pull your straight piece of lumber back and forth over the spot to flatten and level it with the rest of the subfloor.[7] Hardwood Floors
Glue down engineered hardwood, alternatively. If you don't want to nail down the boards, you do have the option of using adhesive to put engineered hardwood in place. It's a good choice, but won't last as long or be as sturdy as nailed down hardwood. The procedure is very similar to the nail-down process. Follow the adhesive manufacturer's instructions for installation and drying times.[11] Hardwood Floors