So I've read through most of the stick'ed info above and have a some questions about storage specifically and boiler setups in general. Utilizing my existing boiler/mechanical room masonry walls I can build in two non-pressurized storage tanks of 750 gl per. One tank would be oriented horizontally and the other vertically. I'm assuming vertical orientation is preferable, correct? If so, assuming equal tank size and insulation is there a quantifiable gain? Anyone ever used fiberglass for a tank liner? The FRP would not be relied on for structural strength, only as a watertight barrier (vinylester resins). Quantifiable gains to using a pressurized tank vs non? Less pumps and HX's for sure, but is the thermal extraction more efficient? Cape of 1955 construction, footprint is 1350', finished basement so 2700 sq' to heat (only attic upstairs); brand new Trane OHWB, base board distribution; lined brick chimney, 3 flues. House is actually very tight, but R20 walls and R20 ceiling don't hold much heat for very long. Big improvements to the thermal envelope will, overtime, bring the Btu demand of the house down. After the boiler is online I'll start replacing much of the HWBB with underfloor radiant. Looking at the Eko 25, primarily because of price; though the V's, Froling, Biomass, and Attack look very nice. But they are out of my budget. The 25 will be undersized from the start but in 3 to 4 years things will be much improved. Thanks for any and all comments and thoughts.