Why do I detect voltage on my ground of surge protector?
More information needed. 

What do you measure "energy on  ground" RELATIVE TO ?
If it was a hard ground you'd see 100 VAC from lobe to ground. If it is a low resistance ground your meter resistance will affect the result. 

For a metwer connected from Vmains to "ground"
Vreading = Vmains x Rground / (Rground + Rmeter)

Some testers measure to local capacitive ground - sometimes the user touches a rear contact as a reference and their body capacity to "ground" is used as a reference. (Try not to "test" 10 kV circuits using these )

You say vent duct work resistance (to "true" ground?) was 20 Ohms. How do you know?

Be aware that by adding a low quality local ground you may INCREASE the risk of electric shock. See my answer to How does earthing work when earth is dry? to see why.