Long run from trunk

8 years ago

One of my upstairs bedrooms has a single supply vent installed above the window. The main trunk (solid ducting) runs through the middle of the attic and services 10 other vents. All the vents are served by flexible HVAC lines branching from the main. The problem is that bedroom doesn't heat or cool as well as the rest of that zone. It is the longest run from the main trunk-estimate of 20 feet. If I decided to install solid ducting for about half the length of that run, would I get better volume in that bedroom? Or perhaps there's another way?

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Comments (4)

klem1
8 years ago
"If I decided to install solid ducting for about half the length of that run, would I get better volume in that bedroom?" Yes

Or perhaps there's another way? Solid all the way or increasing size but you probably know that.

Before doing anything,make sure there's not an adjustiable damper behind outlet louver and/or where run take's off from main trunk.
sofaspud
Original Author
8 years ago
Thanks, klem. Can only do the first half with solid, because the end half is in an attic space that's inaccessible. The line dives into that bedroom's attic and runs 11 ft. across the ceiling to the vent. What would happen if I (somehow) installed a second supply vent in the ceiling where the line enters the space? I imagine the far vent would get starved, but I would hope the additonal vent would help heat/cool the space even more.
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sktn77a
8 years ago
last modified: 8 years ago
If the branch ducts have dampers, you can open that one room up completely (if it isn't already) and shut down the others slighly to get more air going to that one room. It needs more air either because it wasn't getting enough in the first place or because, being at the end of the line, the conditioned air is getting warmer/colder with the longer distance it has to travel in the unconditioned attic.
klem1
8 years ago
"What would happen if I (somehow) installed a second supply vent in the ceiling where the line enters the space? "

The new vent would undoubtedly be stronger than the existing one if hard duct is run to new vent. I would install hard duct and see if that's enough before installing a second vent. To cover all the bases,step hard duct up one size in case you decide to add another vent.