This paper presents an analysis of the transient thermal performance of dynamic insulation. A modelbased on heat transfer through porous media is introduced, considering two types of boundaryconditions: (1) indoor temperature and outdoor temperature are constant; (2) indoor temperature isconstant while outdoor temperature changes. By solving the model numerically, it is found that for thefirst kind of boundary condition, the temperature profile in the wall will reach steady-state within onehour, when the porosity is high.