A couple of years back we changed the duct work in our crawl space. The returns were not changed because the installer told us that changing that wouldn't add much value. We did an energy audit recently and one of the recommendations was to insulate the return duct work and also seal a couple of leaks. We got some quotes and the cost to insulate and seal the steel return ducts were almost as expensive as replacing them with wireflex ducts. I have a couple of questions. 1. Is it that important to insulate the returns? I know it will be very effective when cooling the house but I don't see that big a value while warming up the house. 2. Is it a good idea to change to returns to flex duct? My husband feels that the quality of the steel ducts we have is way better than the flex ducts. Appreciate if you can share your thoughts.