Boiler question?

[MarkCO]

Radiant heat has a longer lag and the air temp can be a little lower than with a forced air system. The layout of the radiators or heated surfaces has an effect. Even with high efficiency boilers, you don't want to turn zones off or down more than maybe 5 degrees or you will lose some efficiency. Radiant systems are not well understood by some owners and that is essential to getting the best comfort and efficiency. I've worked on numerous lawsuits of claimed deficiencies in radiant heat systems where the problem was improper operation of the system due to the owners runing it like a forced air system. Your specific system may have nuances as well.

If you are so inclined, try running it a few different ways for one month corresponding to your billing cycle. With that data and the heating degree days (HDD) an analysis can be run to tell you what mode is the most efficient.