Walter R. wrote:
I have a one story rancher. My NG furnace is in the attic above the family
room. It is very noisy because it sits right on a 1/2" plywood platform on
top of the floor joists in the attic.

I am replacing the furnace. What is the best way of making sure that the new
furnace will be very quiet?

Carpet underlayment? Thicker plywood? Special soundproofing material? Put
the furnace on springs?

Thank for any input

Whatever you do make sure the furnace is not
vibrating a panel. Carpet underlayment works well
to reduce vibration transmission. Thicker,
heavier, isolated are the key words.