I have a 25+ year old home with a same age central air system that needs to be replaced. I plan to have a 3 ton Carrier Performance system installed but I need to decide if I will have the existing ducts replaced as well.

The current ducts are made of duct (fiber) board and in the attic seem to be insulated on the outside. I need to know if there is any health hazard posed by these fiberboard ducts during the normal operation of the ac system.

One AC contactor quoted me a $9000 price which includes replacing the fiberboard ducts with sheet metal. He stated that the old fiberboard ducts may be releasing fiberglass particles into my house when the air is on.

Another contractor claims that the ducts are in good shape and do not need to be replaced. His price for the same job, but with no duct work is $6000.

Any ideas would be appreciated. I'm especially concerned about air quality in the home.