Boy, that is a tall order. First is the heating envelope, build it tight and insulated well. But both of these can have problems: “Tight” still requires ventilation which points toward a Heat Recovery Ventilator, another piece of equipment to install and maintain. “Insulation” must be well thought out to keep moisture from condensing in the walls. In the old R11 and even R16 packages, the wall never cooled to the condensing temperature of water. Of course that came at a price, heat was moving to the outside through the wall. Next is a look at the available energy sources at the site. Is natural gas available, is there solar potential? Then we do our Manual J load calcs to determine our heating requirements. (Note: no Rules of Thumb here, which leads to oversized equipment, never efficient. Make sure that your heating contractor does the HVAC calculations that takes into account all your construction efforts above.)
It is only then that we look at heating equipment. The choice is endless but we have done our best to minimize the size and therefore cost. Cost not only in purchase but in operation. As you might guess, I lean toward hydronics. Too many advantages in my mind to ignore. Quiet, comfortable, efficient, long life. Actually with a few plumbing tools and a good design, the systems are not that difficult to install. To me hydronics simplifies the whole heating equation from space heating to domestic hot water. If a boiler is the choice, domestic hot water needs might be an Indirect Hot Water tank where the boiler is the heat source through an internal (or external) heat exchanger. One heating device serving all purposes. “The best heating system?” A simple answer to a complex question.
ps: Heat Pumps (Hydronic – Water Style) can also meet Domestic Hot Water needs with the addition of a Desuperheater Exchanger but that is a subject for another post.