The results proved it
Had Windows on Washington come to our house to deal with a temperature problem (we have a 1st floor master bedroom that was consistently hotter than the rest of the house in the summer and colder in the winter). They came out with an infrared camera and showed me exactly where the hotspots where (pretty amazing to see it for myself). They gave us an estimate, were here when they said they would be, the crew was professional, and when they were done it measured the temp by the register, and compared it to the temp in the master, and they were off by .1 fahrenheit. I don't typically write reviews etc... but because I was able to actually measure the difference myself I felt compelled to do this.