I have roof racks on my 2015 LWB cargo TC and was getting a lot of interior noise at a variety of speeds. Since I bought the van used with the racks I didn’t know what the general noise level was without them but I wanted to try to solve the problem without removing them. I found some references online about using butyl automotive sound deadening mat typically used in cars with powerful sound systems. I purchased a 36 sq ft pack of Noico 80 mil sound deadening mat and applied it to the ceiling, the upper sliding door panels and on the rear side upper panels. I have the lift gate so I didn’t put any on the rear door. The interior noise was so dramatically reduced that is seems like I’m now riding in a luxury car. This has been the best value addition to my cargo van.