What was the primary goal for Benjamin Franklin's Pennsylvania Fireplace design?

Reducing the fuel needed to heat a space

Benjamin Franklin's primary motivation when developing his cast-iron stove, sometimes called the Pennsylvania Fireplace, was addressing the severe inefficiency of traditional open fireplaces used for heating dwellings in the mid-1700s. Open fires wasted significant heat escaping up the chimney, necessitating constant tending and large fuel consumption. Franklin's design utilized metal enclosures to retain and direct heat into the room, thus requiring less wood overall to maintain warmth. This differed significantly from later cooking efficiency goals, which focus specifically on the thermal transfer to the food being cooked, whereas Franklin concentrated on maximizing the heat radiated into the living space.