It is impossible to throw grenades (RGO, RGN, Smoke, Light, not IR) through the windows of Land_u_House_Big_01_V1_F. This is true from inside and outside the building. Throwing grenades through the doors is working and strange to say IR grenades can pass the windows. Bullets can also pass the windows.

Here is a video demonstrating this: https://www.youtube.com/watch?v=rr_YhVmHJZo