II am currently designing the heating system for my new home and am hoping for some input from some of the experienced installers/users on this site. Here is an outline of what I am planning: I have a Econoburn 200 which I will put in its own outbuilding, 50' from my house. I will trench in the 1 1/2" boiler return and supply, then spray foam. In my basement, I will have 2 500 gallon propane tanks, insulated. I will feed the boiler into a small tank, like a hydraulic seperator, then plumb off the tank to my 2 basement zones, 2 upstairs zones, and storage tanks. All emitters are in floor, hydronic (concrete). I need higher supply temps upstairs (120F) than downstairs (110F) due to heat loads and pex spacing. The house is a timber frame insulated with spray foam. If it weren't for all the windows, the heat load would be rather small. As it is, in Wisconsin, on a -25F design day, I calculate a heat load of 70,000btu/hr. The upstairs is roughly 2200 square feet, the walkout, full basement, about 2500 sq ft. The house has a lot of mass and takes a day or two for the temp inside to change much with changes outside. I have done a lot of reading and research and am leaning towards the primary/secondary system, using a small tank as a hydraulic separator. I will feed the boiler into the tank, then plumb off the tank to my 2 basement zones, 2 upstairs zones, and storage tanks. All emitters are in floor, hydronic. I need higher supply temps upstairs than downstairs due to heat loads and pex spacing. I understand the need for boiler protection and will most likely use one of the packaged loading valves in the primary loop. Now, where I am confused is how to best arrange my secondary system. I see four likely scenarios: 1. Separate circulators and zone valves for each of the 4 zones. 2. Separate circulators and modulating mix valves for each zone. 3. A variable speed circulator feeding all zones with zone valves for each zone. 4. One variable speed circulator and zone valves for basement 2 zones and one variable speed circulator and zone valves for the 2 upstairs zones. I understand the the basic pros/cons of zone valves, one circulator versus multiple, etc. But wonder if the specifics of my system would cause one design to be favored over another. I am leaning towards the single variable speed circulator and zone valves due to electric costs, but like the redundancy of the multiple circulators. Would greatly appreciate any advice, especially if there is yet another secondary system I haven't mentioned that would be better than those I have mentioned.