这是一项研究动态或时变的热量流入和流出建筑结构，以及由此产生的室内空气温度模式的研究。目前在计算负荷和选择设备尺寸方面的许多实践主要基于稳态假设和技术。由于天气和气候模式的变化，实际的传热过程是动态的。因此，每小时、每天和季节性建筑性能的分析和预测应基于动态考虑。Fourier（1）首先解释了计算此类系统瞬态传热的理论和基本数学，但计算的复杂性以及所涉及的时间和费用有时阻碍了建筑师和工程师使用如此复杂的程序来设计和评估建筑物。 在某种程度上，简化稳态方法已经并仍在与工程判断结合使用。引用:ASHRAE Transactions，第80卷，第2部分，魁北克省蒙特利尔

This is a study of the dynamic, or time-variable, flow of heat into and out of the fabric of a building and the resulting temperature patterns of the indoor air. Much of the present practice in calculating loads and selecting equipment sizes is based largely on steady state assumptions and techniques. The actual heat transfer processes are dynamic because of the changing patterns of weather and climate. Therefore, analysis and prediction of hourly, daily, and seasonal building performance should be based on dynamic considerations. The theory and basic mathematics for the calculation of the transient heat transfer of such a system were first explained by Fourier (1), but the complexity of calculation and the time and expense involved have sometimes deterred architects and engineers from using such sophisticated procedures to design and evaluate buildings. Simplified steady state approaches have been and are to some extent still used in combination with engineering judgment.