What heater for our older home?

My hubby, Josh, and I bought a home that was built in the early part of the 18th century. The home is very large plus it has some uniquely beautiful features. There’s an enormous front porch, lots of tall windows, high ceilings, plus gorgeous woodworking. There are large closets, multiple stairways, plus an amazing view of the little pond in the backyard. There are also numerous negatives to having an older home. All of the hardwood floors and all of the stairs creak whenever anyone walks on them, plus they are really cold when it’s winter. A handful of the aged windows open, but the others don’t, but they all leak air. Because of the high ceilings, cavernous rooms, plus the lack of insulation, the old house is a big challenge to heat in the cold season and it’s also hard to cool in the warm season. The walls are too thin to accommodate any conventional HVAC ducts. We’ve lived in the old house for several years now, and over that time we’ve made gradual improvements. Top priority was to install an effective plus energy efficient heating system. To avoid doing major renovations, the two of us decided on a boiler system, because installing a boiler in the basement, plus incorporating baseboard heaters, was not really that overly intrusive. Although the boiler is quite powerful (plus it’s wonderfully energy efficient), it was initially having some trouble keeping up with the demand of such a large house, plus it was costing us quite a bit every month. We knew we should probably improve the level of insulation in the walls and update the windows, caulk the doors and weatherstrip them to eliminate waste. So now that we’ve solved the heating problem, the two of us are looking into a/c for the summer. We are in the middle of a debate about portable air conditioners, high velocity a/c, or ductless units and which one is best.   

gas heater