I can't speak to the in-floor radiation, although it sounds marvelous. We just did a retrofit of our 1910 whole-house hot water heat using the original castiron radiators. To our surprise and continuing delight, a new German high-efficiency direct-vent boiler with Triangle hot water heater has saved us over 50% each month over our old bills. We now have tons of heat, and we're in Maine. Do make sure that your original cast-iron radiators aren't repipable before replacing them? They don't make 'em like that any more, etc etc. For the addition, that's always tough. We removed a radiator in our kitchen, but made up for it a wee bit by relocating the laundry room directly below it in the basement. I'd kill for in-floor in my kitchen, but it is indeed terribly expensive. Up to you to decide what the priority is -- it certainly would be a very understandable outlay in cold climates like ours, and potentially could be paid for by the expected savings with the new boiler?

I love all of your comments, thank you so much! You are all so much smarter than me at this. J I now have clarity on which direction to go. I completely agree—and hadn’t thought about—making the marble into a piece that is a non-permanent part of the house we can take with us. I may also try to incorporate it into at least one element in the house but will make that decision down the line. I am going to purchase a few of my favorite pieces now and worry about it later. I told my husband also that I would love a dining room table if we can get a large enough piece. Once this is all said and done I will definitely let you know what we did and post final-product pictures. (haha in a year or so I would think) And msmeowàI live in Tampa so take solace knowing that not all in/near Central Florida use a scorched-earth approach!

Those boards were probably never meant to be exposed as floorboards, but would likely have had a linoleum or rugs or oilcloth for low maintenance. There's no reason not to have them as finished floor now, however, if you can live with the dust-attracting gaps! If they're pine, it's quite hard to get a paint to wear well, because even old pine is a bit soft and scuffs easily. I think if I were you I would finish them with Rubio Monocoat, which now comes in a variety of stains, which you might find wears better than a paint. It's lovely stuff to work with, absolutely no VOCs, and you only need one coat, so although it's expensive there's no waste, you won't be choking and crying on toxic fumes, and you'll be done in a day. Takes a few days to cure completely. I already shared this link once this evening, lol: http://www.monocoat.us/2C-Oil/ They're a lovely company to work with. Lots of informative videos on Youtube, and you can talk to them on the phone as well.

I live in the Midwest where we are blessed with real winters and buggy summers. We put triple track storm windows on our last house because we weren’t staying and didn’t want to invest in thermal windows. I was pleasantly surprised at how easy they were to put on and how really well they insulated. We were able to match the exterior color of our house trim and the sash height so they looked appropriate on the outside. Not replacing the window meant that we didn’t have to worry about messing up the interior aesthetics of an old house. Plus, screens are great for summer so you can open up your house. Honestly, if the windows in our current old house had been in good shape and functional I would have considered using triple tracks again. The only real downside is washing but I can hire a lot of window washers for the cost difference. So much better than what I remember as a kid!!