take the hinges apart. Spray it on the joints of the hinges, work the door open and closed a few times to distribute the lube, then wipe off the excess with a paper towel. Takes less than a minute per door.

heating. It won't boil your feet, but it will produce enough heat to warm your house. This is true for most places, anyway. I've been in hotels in Korea when it was aroud -10F outside and the rooms were a comfortable 70-75F using just subfloor heating. Consult a local installer, they might have a demonstration available.

The upfront installation costs are a bit high, but when you factor in that it replaces your forced air heating system with a much more efficient style, the benefits start to stack up.