Lower heat loads make more design options available.
Preparing an accurate heat loss or a peak design heating load calculation is the foundation of an efficient and effective radiant heating system. I say “efficient and effective” because before the mid 1980s, when the modern wave of radiant heating found its roots, sizing a heating system was more an art than a science. It was hard to find any boiler with a Btu/hr output of less than 125,000, and the controls that regulated many hydronic systems were limited to a single (line voltage) thermostat, operating high-limit aquastats and a BIG pump.