Btu (I.T.)
The British Thermal Unit (International Table) is a unit of energy commonly used in the United States defined as the amount of heat required to raise the temperature of one pound of water by one degree Fahrenheit at a constant pressure of one atmosphere.
Foot-pounds
A foot-pound (ft-lb) is a unit of work or energy in the Imperial and U.S. customary systems that is the amount of energy required to exert a force of one pound over a distance of one foot.