"It depends" is a very good description for all of this. There are so many environmental factors to turn and tweak, and each one will have its own effect on the outcome.
However, knowing the basics can at least lead to some understanding of "better" and "worse" - for example, the inverse square law (intensity/energy falls off at the square of the distance). Furthermore, simple forms of shielding can make the intensity/energy fall off faster.
The flashlight example is the best analogy I've run across. Some materials will absorb the energy, others will reflect it, and some can even concentrate the reflected energy (i.e. black cloth, mirror, and concave mirror, respectively, for a flashlight).
As for shielding the fridge, just electrically connect the insulation to the conduit that the refrigerator is plugged in to.