I was initially skeptical when I heard about this service but after doing some research, I discovered the US department of Energy recommends this method as the only way to seal ducts hidden behind walls and ceilings that can't be manually sealed. This company was great. Joe and his team were neat, efficient, friendly, and incredibly thorough. To my surprise, Joe went far above and beyond the scope of the job to fix problems by hand and identify furnace issues that had nothing to do with the actual job I contracted for, all for no additional charge. Now my ducts are running 20% more efficient, more than 90% of the leaks have been sealed, and I'm finally getting heating and cooling to rooms that were previously either ice cold or blisteringly hot. I highly recommend these guys!