degree Fahrenheit hour/Btu (IT) Unit Converter

Definition of degree Fahrenheit hour/Btu (IT) unit

Degree Fahrenheit hour per Btu (International Table), written °F·h/Btu(IT), is a unit of thermal resistance. It describes the temperature difference in degrees Fahrenheit required to sustain a heat-transfer rate of one British thermal unit (IT) per hour.

History of degree Fahrenheit hour/Btu (IT) unit

The unit developed from the British engineering tradition of expressing heat flow in British thermal units and temperature on the Fahrenheit scale. The Btu was historically defined through the heating effect on a pound of water, while the International Table Btu was standardized as 1055.056 joules to improve consistency. Combining an hourly heat-flow rate with a Fahrenheit temperature difference produced the practical resistance unit °F·h/Btu. It became common in North American heating, ventilation, air-conditioning, and building-insulation practice, alongside the SI unit kelvin square metre per watt.

Applications of degree Fahrenheit hour/Btu (IT) unit

Today, °F·h/Btu(IT) is used mainly in the United States and Canada to rate building-envelope components, insulation, windows, doors, roofs, and walls. Engineers may use it for furnace and duct insulation, equipment heat-loss calculations, and thermal-resistance tables. For comparison, values can be converted to the SI unit K/W; one °F·h/Btu(IT) equals approximately 1.895 K/W.

Complete list of degree Fahrenheit hour/Btu (IT) unit conversion