Why use aluminum foil that's going to be opaque.

You can use a transparent material, like aluminum window screen mesh, as long as the spaces in the mesh are small compared to the wavelength of the electromagnetic radiation you're wanting to block. That way, you can still enjoy natural light inside your trailer and look out the window to see if it's raining while still being able to block all Sunday morning Evangelical Christian radio and TV shows.

I have a Julio filter on my sound system's tuner. Whenever anything by Julio Iglesius comes on, it automatically changes the station.