Foams are an important component of various inertial confinement fusion target schemes. The propagation of shock waves in foams is also an important issue for many other laser experiments (e.g., laboratory astrophysics experiments). The usual approach is to assume that the foam can be considered as a homogeneous mixture. Taking into account the effects of foam heterogeneity leads to increased shock velocity and reduced compressibility. Evidence of this effect is obtained using two-dimensional adaptive mesh refinement Eulerian numerical simulations. Nonetheless, for the very low density foams filled with DT ice used in recent direct drive target designs, the homogeneous mixture model provides adequate shock timing, density, and pressure profiles.