While performing home investigations, I have noticed that I would get extremely high EMF readings throughout the entire basement or really low, close to the floorboards. From experience, I start to scan the water pipes, and I usually find this to be the source. What causes this phenomenon is that in older houses, the fuse box is grounded to the water pipes. If there is a problem in the fuse box, then there will be an electrical current flowing through water pipes, thus generating an EMF field. I have scanned water pipes and seen improperly grounded fuse boxes cause readings of over 400 micro gauss (a standard K-2 meter indicates red at 20 micro gauss).
Now I have also found EMF readings in houses that do not have electricity. Once again, check the water pipes. A home with an improperly grounded fuse box can cause EMF readings in neighboring houses. What happens is a house with an improperly grounded fuse box can energize the water pipes running throughout an entire neighborhood. I have overheard my local city utility workers talk about disconnecting a water line from a house and witnessing the porch lights getting brighter or getting shocked as they disconnected water lines.
So if you’re investigating a house that has unusually high EMF readings, scan the water pipes and then check to see if the fuse box has a grounding wire running to a water pipe. Also, never attempt to do anything to a house's electrical system unless you're a certified and licensed electrician.