We live in a house that is approx. 1200 sq ft. and was most likely gutted and 'refactored' by the previous owner. In our laundry room, they built a 'closet' around the water heater and our HVAC unit. In this 'closet', there are two metal tubes or ducts that are circular in shape, about 8 inches in diameter, and almost four feet long. You can shine a flashlight up through it and see the wood at the top of the house.
I have a few questions about these:
What could they be (or have been) for?
Would these be causing efficiency problems?
Should they be removed and the holes filled in?