Welcome to the site AC Hacker. I'm in a similar boat. I have an older 1800s house that I'm just starting to remodel to get additional insulation into the walls (also thickening them for added insulation). I was also planning on going with in floor radiant heat. One room of the house already has it and it is simply wonderful. Its currently running off the hot water heater (blah). I was thinking about going with a conventional high efficiency boiler as a backup for solar hot water heat. But, your heat pump is very fascinating and I'm excited to see where it goes! Feel free to bounce any ideas around on here. We'll do what we can.