splitting lines from boiler

So I'm wanting to heat my 1000 gallon storage tank from my biomass 40 boiler. The boiler is in an outside garage, and storage is in house, so I need to pipe the lines underground. I've been thinking about using thermopex, but it only comes in 1-1/4 as its largest diameter. I'm afraid that won't move enough heat to allow my boiler to run full bore since 1-1/4 pex has a max flow of 11.2 I'm thinking I'd need a flow of at least 14.

Another thought was to split a 1.5 inch line and run dual 1" pex lines underground, and then go back to 1.5 once i get to the house. But i didn't know if this is even possible or a good idea. Anyone have similar experience piping from OWB to indoor thermal storage?

hey thanks foamit up. I plan on doing the spray foam option that you suggested, because it seems to be the least expensive/most effective method. As you mentioned though, you can pipe to storage with the 2 inch pipe, which allows you to transfer all that heat efficiently. If i used the 1-1/4 to run to my storage, i'd only be able to extract about 110,000 btu per hour, and my boiler is supposed to put out 140k. I may have to settle for less, I just really don't want to be idling the boiler.