I am gong to replace my furnace, it was in the house when I moved in 17 years ago,
And I have had problems lately,
My house is about 30 years old. My question is should I replace the duct work when I replace the furnace? I do not see any problems. My only though is they may be old and dirty, as well as have problems I can't see,
Thanks
Ron

If you do not have existing problems, your ducts should be fine. You may want to have the installer clean your ducts. It may be a few bucks cheaper since he will already be on site. Every time I have gotten an estimate from a HVAC guy they evaluated my ducts to insure they could handle the new volume of air.