What is a BTU and its significance in HVAC?

A BTU, or British Thermal Unit, is a measure of energy capacity that specifically quantifies the amount of heat energy required to raise the temperature of one pound of water by one degree Fahrenheit. In the context of HVAC (Heating, Ventilation, and Air Conditioning), understanding BTUs is crucial because it helps in sizing and selecting heating and cooling equipment appropriate for a given space.

When designing an HVAC system, determining the BTU requirements for a building allows engineers to ensure that the system can provide adequate heating or cooling to maintain comfort levels. This measure is integral in calculating heat loads, ensuring energy efficiency, and achieving effective climate control.

The other options do not correctly define what a BTU represents. For instance, while it relates to temperature changes in a specific context, it does not serve as a direct measure of temperature itself. Similarly, though pressure and airflow are important factors in HVAC systems, they are not what a BTU measures. Thus, option B accurately emphasizes the significance of BTUs in terms of energy capacity in HVAC applications.