I have an oil boiler runs around 85% efficiency. Right now it has a direct coil in it.
I've been thinking of getting an indirect water tank to increase the efficiency of the house hot water, plus I've got 3 kids it makes sense.
So looking around I was thinking I get through the whole summer/spring using less then 1 tank of oil. During the winter I end up getting 1 or 2 tanks, depending on how cold. Mainly because we have baseboard heating in the basement (which my wife leaves on set to 68 during the cold winter days since it heats up the 1st floor, (and with the kids on the floor it makes sense) The HVAC keeps the rooms themselves warm enough, but the basement heat really helps. In any case I was thinking it'd be nice, if the baseboard heat could be heated when needed via a 2nd coil in an indirect water tank?

Basically as follows:
Bottom coil of tank is heated via the boiler.
Top coil when there's call for it would run a pump that would run water between the indirect tank and the baseboards.
There would need to be something to add more water to that circuit when needed.

Any thoughts?