You have to trust the company
Did you know that some HVAC companies work with sheet metal? The reason HVAC businesses would work with a sheet metal business is for ductwork. When I got my central HVAC installed, I did not realize how well I picked out my HVAC provider. I just picked a HVAC dealership with good reviews. I decided on central HVAC for my big house since the HVAC contractor said it was a good idea. Typically, a HVAC company does the HVAC set up, and then has to hire out for the ductwork to be made. A separate business makes the metal and uses the dimensions the HVAC business gives them. The ductwork is then sent to the HVAC company and a HVAC provider installs it. It is a lot of wait around time and also, possible error. If the measurements are not exact, the HVAC ducts can get twisted or bent. Also, the ductwork could get setup not correctly and allow air to leak out. With my HVAC business, the metal people worked right with the HVAC people. The sheet metal guy came in and used technology to measure the home. There was no human error element. The technology then cut the metal as well. The ductwork installation took half the time than most companies. The air ducts were the exact right size and did not get dented in transport. My central HVAC system is perfect because of the HVAC company that I choose. Talk about luck of the draw right? Ductwork maintenance and HVAC service will go better I bet too.