Measuring ducted heat pump system static pressure loss w/ central return & reducing central return noise – GreenBuildingAdvisor

Thanks, is this sketch describing what you’re saying re: duct board? (You’re saying the duct board should be on the inside walls of the riser, right? Based on what you’re saying, they sound to me like both pieces are on the same inner face of the riser: the part opposite the filter opening, right? And just small pieces, like 2 ft max, not the entire length of the riser? Or the entire length)?

Also, do you think making the filter opening larger—from, say, 12 by 24 to 12 by 36”—would make things quieter?