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Discussion Starter · #1 ·
Hi


I have my HT design mostly done, except for the HVAC setup.


The room I have has brick walls, and I am building a decoupled drywall room within it.


The house is also getting new ducted air con.


What I'm trying to accomplish is an inlet and return that doesn't compromise the decoupled room I have created. I especially want to keep air noise down to a minimum.


I should also point out that the AC designer has stated a 12" duct for the inlet for the room. And there is no fan unit running inline either.


Here is my proposal.


I have two columns at the front with low air return vents. I have designed these so that combined they are the equivelant area (actually larger) of the 12" inlet ducting. These I have designated red.


The inlet is in the back corner and is green.




Now its not practical to run the duct in a winding fashion through the columns with insulation (dead vent style), so I was planning on mounting the ducting to the top of the columns above the ceiling.


The columns would wind down on the inside as in the picture, and have the walls lined with insulation. The idea is the sound will be forced to go around corners, and hopefully will be absorbed as it goes. And hopefully I don't just create air turbulence in the process.




Will this work? or am I wasting my time ? Or do you have a better idea?
 

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Discussion Starter · #3 ·
Hi Dennis


Why is that ? The ducts run throughout the house in the ceiling, and I wouldn't have enough column width to be able to run down and back up again, if that's what you had in mind?
 

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Can you run that design past your AC designer for an opinion? Seems to me that all the angles would restrict your airflow. Question is to what degree.
 

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You want to extract hot air. Hot air rises ... returns near the floor pull the cooler air out of the room. Supplies ... Cold air falls. So, when cooling ...


Cold air enters the space (not blocked by people, seats) and falls toward the floor (actually cooling something other than your toes). The hot air rises toward the ceiling and is extracted ... good flow, good circulation, no stratification.
 

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Quote:
Originally Posted by SierraMikeBravo /forum/post/19609178


Ooooooo! I like that!

Gets me a little hot too SMB (
) (or cool depending on which layer you're in).
 

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Discussion Starter · #9 ·
Thanks Dennis, that makes perfect sense.


Is ther any point then in trying to run air down then up a column. I'm thinking no.


Hey I could create my own inversion layer!


I will also run this past the ac designer who is coming later this week. That's why I wanted other opinions first.


I will also use acoustic ducting as suggested.
 

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Discussion Starter · #10 ·

Quote:
Originally Posted by Dennis Erskine /forum/post/19607180


You want to extract hot air. Hot air rises ... returns near the floor pull the cooler air out of the room. Supplies ... Cold air falls. So, when cooling ...


Cold air enters the space (not blocked by people, seats) and falls toward the floor (actually cooling something other than your toes). The hot air rises toward the ceiling and is extracted ... good flow, good circulation, no stratification.

Dennis, won't the opposite be true when I want to heat the room ?
 

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The room will heat up fast given that it's sealed and so insulated. If the columns are not acting as mufflers, can you build a "soffit in the joist cavity?" Similar to the soffit details I sent you?
 

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Discussion Starter · #12 ·

Quote:
Originally Posted by Ted White /forum/post/19622179


The room will heat up fast given that it's sealed and so insulated. If the columns are not acting as mufflers, can you build a "soffit in the joist cavity?" Similar to the soffit details I sent you?

Hi Ted,


no, unfortunately no room. The existing ceiling is raked. The new one is stepped, which leaves very little usable space between the two.


The best I could come up with is a 15"x15"x4' long box. I could make one of these each side of the room, one for in and one return. Given the tight spaces I would need to use some of the box as a 90 degree turn to connect to the vent in the ceiling.


Given the duct will be 12" diameter I'm not sure I have enough space to make much difference.


Here is a couple photos to show you what I am working with.


This is the back left corner of the room. It corresponds to the green column in the first picture above.



 

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Why did you run your hat channel vertically on the wall vs. horizontally? Not following that one.
 

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If there is any way to make a chase or build out of some kind to run the ducts in? This could be as simple as drywall or as decorative as milled oak panels.

The ducts need a certain amount of space/size to operate/perform correctly. Some design compromises may have to be made for the best hvac operation. I do hvac for a living, believe me do not skimp on the duct design. All the money,sweat and time spent on your HT won't be worth it if you aren't comfortable inside it...
 

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check out my build thread for an example of putting a return air duct in the soffit and locating the fan outside the room. It works very well and the fan cannot be heard inside the theater, only a barely audible sound of air being sucked through the vent.
 

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Discussion Starter · #17 ·

Quote:
Originally Posted by fotto /forum/post/19624516


Why did you run your hat channel vertically on the wall vs. horizontally? Not following that one.

That was the way the Australian distributors told me to install it. I spoke at length with him regarding this, as I had planned to do it horizontally. He said on brick walls they always go vertical.


Providing the spacing is the same, it shouldn't make a difference, should it?


It does have the small advantage of less drywall cutting as the sheets can be longer.


And yes, it was a fun couple days on the hammer drill !
 

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I imagine that the weight of the drywall coupled with the vibration of the wall overtime will slide the channels in the clips down until the the drywall is mashed firmly to the floor. So I'm guessing that is where they should be installed in the beginning to minimize any future movement. This is different than typical installation where you leave a slight gap.


Did your distributor mention using any kind of gasket for the bottom of the drywall?
 

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There are times when a vertical installation of channel is needed. In such cases run the channel so it stops at the floor and will go no farther. You may need to consider any moisture wicking from the floor.
 

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I had similar concerns Big when I saw that, although I made an assumption that the channel should be touching the floor at the bottom pre drywall to mitigate the "sliding down" due to loaded drywall weight that would seem to be inevitable.


Subsequently, I would then have concerns about losing some resiliency due to that the channel will be "grounded" to the floor, at least through some lower portion of the wall.
 
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