An old vented space heater
tape to seal an old register. Not the right tape - won't last.
water heater well-insulated with fiberglass jacket
old 70% efficient gas furnace.
Note the mastic used to seal the duct seams
Well-taped register
water heater insulated with bubble wrap. This is not a good material to use.
An old gravity furnace in the floor
an open filter slot in the return duct means a poorly working duct system
well-insulated water heater
Ductwork under an evaporative cooler tends to rust a lot
a duct boot sealed with mastic
well-insulated water heater pipes