A unit of measurement equal to a difference of one degree between the mean outdoor temperature on a certain day and a reference temperature, used in estimating the energy needs for heating or cooling a building.

• 度－日一测量单位，等于某一天户外温度的平均值和一参照温度之间一度的差别，用来估计加热或冷却一座建筑物所需要的能量