There is a lot of confusion about delivering enough BTU vs. reaching a heating target in the industry. The two, although connected, are not the same. Even professionals whose job is to install heating systems often struggle reconciling this fact.

When engineers and us designers calculate heat loss for a structure or a driveway, we first figure what the Winter Design Temperature, the temperature on the coldest day of the year is. The other 99% of the year, the temperature must be above...