First thing I'd have to ask is do you really need that 180-degree water in the buffer? Maybe on a really cold day, but how often do they really occur? Maybe a lot in Calgary, but still. If that were allowed to cool off on a mild day, you'd reach better efficiencies. Does the thing have an outdoor reset control input? Is it being used? Adjusting the buffer tank based on the heating needs would be better. Then, you'd have to decide, do you really need the buffer tank at all? Often, they're added to help fix an oversized boiler and improve its efficiency.