The measure that uses 65 degrees Fahrenheit and the average temperature of any 24-hour period is called degree day.

• A. Degree day
• B. Heat index
• C. Humidity ratio
• D. Cooling load factor

Answer: (A)

Degree days are a weather-based index used to estimate energy needs for heating or cooling. By using a base temperature of 65°F and the daily average temperature, you quantify how far outdoor conditions are from that base on a 24-hour period. If the daily mean is below 65°F, you get heating degree days equal to 65 minus the mean; if it’s above 65°F, you get cooling degree days equal to the mean minus 65. Adding these over time helps predict how much energy will be needed to maintain indoor comfort. Heat index blends temperature and humidity to describe how hot it feels, not energy requirements. Humidity ratio is about moisture content in the air. Cooling load factor is a separate metric used in load calculations.