Fatplumber --
I should have explained better. This is a forced air gas furnace, and I want to cover around 1/2 of the surface of the cold air return with a piece of furniture. I'm guessing that I shouldn't.
But would it be OK if the piece of furniture is 2" off the ground, so the cold...
The cold air return grate for my central heating system is 13.5" (front to back) x 23.5" (along the wall). Can I put a piece of furniture (piano) over the back 7" of the grate (with no clearance underneath), so I'm left with 6.5"" x 23.5" How much would it help if I put the piano 2" above the...