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Boltino
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#1
2nd December 2010
Old 2nd December 2010
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HVAC Baffle Box Questions

Hey folks,

I'm in the process of finishing off a basement home studio. I've done a good bit of searching on my particular questions and haven't been able to come up with anything definitive so I thought I'd start a new thread. I want to build a couple of "baffle boxes" for my HVAC supply vents. The main purpose of these is to stop sound transfer from the studio to the living space upstairs. All of the HVAC runs off of the same branch duct so standard HVAC ducts would provide a fairly direct path to the upstairs. I've found some info but I had a couple of specific questions:

1) My baffle boxes will be inside the ceiling joist cavity; is there any need to build a separate box containing the baffles? I was considering utilizing the joist cavity as the baffle box, mounting some 1/2 drywall for mass, mounting the baffles, then using duct liner on all of the surfaces. I realize isolating the box totally would likely be better but the space in the ceiling is small and I'm trying not to restrict airflow too much. I'm not in need of total isolation, just trying to improve on standard HVAC construction. For reference, the plan for the rest of the room is to fill the joist cavity with fiberglass insulation and mount two layers of 1/2" drywall with green glue in between. I'm trying to keep the HVAC access points from being a weak link.

2) I can't seem to find any place to purchase JM Super Duct to line the baffle boxes. Are there any online retailers or equivalent products that might be more readily available? I only need a couple of panels of it.

Thanks so much for your time!
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2nd December 2010
Old 2nd December 2010
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Your plans sound resonable.

Running a separate duct back to the AC is probably a better idea.

Don't forget the returns.



-tINY

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3rd December 2010
Old 3rd December 2010
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Quote:
Originally Posted by tINY View Post


Your plans sound resonable.

Running a separate duct back to the AC is probably a better idea.

Don't forget the returns.



-tINY

Thanks Tiny! I definitely agree that a separate duct back to the AC would be superior; unfortunately I'm somewhat constrained by the existing system and don't have the budget to make those kind of changes. I think the baffles will get me in the range of reduction I'm shooting for.

The return is also existing and isn't in a position to have any baffles added. I am planning on lining the duct (it is over-sized to accommodate this); the return isn't as much of a concern as it has a much longer path (with more turns) to upstairs connections.

Thanks so much for your time!
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3rd December 2010
Old 3rd December 2010
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Are you sure about connecting the house system to the studio?

I did it in my current studio and would NEVER do it again. It's bad for isolation and because the needs of a control room differ so greatly from the rest of the house.

I'm about to build a new studio actually and will be using separate mini splits for the CR and studio.
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Boltino
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3rd December 2010
Old 3rd December 2010
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Quote:
Originally Posted by drew View Post
Are you sure about connecting the house system to the studio?

I did it in my current studio and would NEVER do it again. It's bad for isolation and because the needs of a control room differ so greatly from the rest of the house.

I'm about to build a new studio actually and will be using separate mini splits for the CR and studio.

Sadly, yes it will be connected to the house system. Being that this is really just a project studio, I don't have the budget to separate it properly (the HVAC was already in place in this area of the house; I'm just modifying it a bit). I'm really trying to utilize a few DIY methods to knock down the dbs a few notches.

Thanks so much for chiming in, I'm sure that would be a significantly better option! thumbsup


As an update, I was able to find a ductboard locally (owens corning quietR). The current plan is to add two layers of 1/2 drywall to the bottom of the upstairs floor, mount plywood baffles to the joists and line the cavity with quietR. I've got a gasket collar I'll be using to tie the supply in and I'll cut in an oversized register on the far end of the baffle box.
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3rd December 2010
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In the summer, my studio is hot while you could hang meat in the rest of the house. In the winter, I am opening the window in the studio to let the heat out.

You have been warned!!
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3rd December 2010
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Originally Posted by drew View Post
In the summer, my studio is hot while you could hang meat in the rest of the house. In the winter, I am opening the window in the studio to let the heat out.

You have been warned!!



*weeps softly*
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6th December 2010
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Quote:
Originally Posted by Boltino View Post
Hey folks,

I'm in the process of finishing off a basement home studio. I've done a good bit of searching on my particular questions and haven't been able to come up with anything definitive so I thought I'd start a new thread. I want to build a couple of "baffle boxes" for my HVAC supply vents. The main purpose of these is to stop sound transfer from the studio to the living space upstairs. All of the HVAC runs off of the same branch duct so standard HVAC ducts would provide a fairly direct path to the upstairs. I've found some info but I had a couple of specific questions:

1) My baffle boxes will be inside the ceiling joist cavity; is there any need to build a separate box containing the baffles? I was considering utilizing the joist cavity as the baffle box, mounting some 1/2 drywall for mass, mounting the baffles, then using duct liner on all of the surfaces. I realize isolating the box totally would likely be better but the space in the ceiling is small and I'm trying not to restrict airflow too much. I'm not in need of total isolation, just trying to improve on standard HVAC construction. For reference, the plan for the rest of the room is to fill the joist cavity with fiberglass insulation and mount two layers of 1/2" drywall with green glue in between. I'm trying to keep the HVAC access points from being a weak link.

2) I can't seem to find any place to purchase JM Super Duct to line the baffle boxes. Are there any online retailers or equivalent products that might be more readily available? I only need a couple of panels of it.

Thanks so much for your time!

Most HVAC ducts are sheet metal. Use an insulated flex duct, the ridges in the flex duct make it a quieter alternative. The flow is slightly reduced however the sound isolation is better.

Make sure to replace all of the rigid 6" duct. This eliminates any mechanical connection to the main supply duct.

A flex for the return will help also.

Making a "Baffle box" may impede the air flow.


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6th December 2010
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Quote:
Originally Posted by drew View Post
In the summer, my studio is hot while you could hang meat in the rest of the house. In the winter, I am opening the window in the studio to let the heat out.

You have been warned!!
I hear this phrase echoing in the heads of many that did not listen!
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6th December 2010
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6th December 2010
Old 6th December 2010
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Quote:
Originally Posted by Haz-Mat-Strat View Post
Most HVAC ducts are sheet metal. Use an insulated flex duct, the ridges in the flex duct make it a quieter alternative. The flow is slightly reduced however the sound isolation is better.

Make sure to replace all of the rigid 6" duct. This eliminates any mechanical connection to the main supply duct.

A flex for the return will help also.

Making a "Baffle box" may impede the air flow.


Thanks for chiming in! I actually built about 3/4 of each baffle box this weekend.

I'm sure flex duct would help but I think in my case, baffles would be needed regardless (I'm no expert though). Even with flex duct, it would still be a short straight connection to the main chase; I would worry about significant transfer since I couldn't utilize any bends. That's why I chose the baffles; my hope was that they would provide maximum sound stoppage in the shortest linear distance.

There is a short run of existing galvanized duct that I had considered replacing with flex between the baffle box and main chase but I decided to leave i; I'm a bit worried that flex + baffle box would decrease the flow too much. The connection to the baffle box utilized a rubber gasket to decouple the two parts of the system so I'm not overly concerned about vibration traveling down the duct.

Airflow is definitely a concern. Based on conversations with my HVAC guy, the studio room is right in between needing 1 or 2 supply ducts. I decided to utilize two with baffle boxes; my hope is that any restriction will still provide above what 1 single duct would supply. I was also able to increase the area of the passage through the baffle box from what the 6" line supplies. I'm sure the turbulence in the baffle box will restrict the flow somewhat but, again, my hope is the total supply will still fall in the proper range.

Quote:
Originally Posted by RonT View Post
I hear this phrase echoing in the heads of many that did not listen!
I'm sure this is the case! I would have loved to go "full on" with this project but at the end of the day; it's a project studio in my residence and I couldn't justify that much $$. I do spend a significant amount of time in there, but it's not my day job.

I couldn't justify the $$ for a separate system and I didn't want to risk compromising the system's performance in the rest of the house. Basically I approached it from the basis of standard room construction (utilizing the majority of the existing structure and HVAC system) with a few cheap DIY methods to control sound transmission and treat the finished room. Will I regret this approach down the road? I give it a 50/50 shot.
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6th December 2010
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7th December 2010
Old 7th December 2010
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Give me a break, guys. If you have a modest home studio, properly ventilated, and install dampers in the right places: The worst that's gonna happen is that you don't cool the rest of the house very well when in your studio...



-tINY

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26th January 2011
Old 26th January 2011
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If not too late, there is the option of a portable AC unit in the room and just run it during breaks. They are 110V and just need to be vented out. The winter option is to swap for a space heater cranked during breaks. If well insulated, this may work. Just thought I would throw it in. On my build, I have these in the next room and just vent between rooms. We are not up and running yet, but this idea has some support.
Good luck with everything.
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