My brother-in-law recently renovated a building that he's using for party rentals and a portion of it has a hair salon in it. There are a couple of rooms in the back of the building that are not being used, so he told me that I could use it for free for a practice/recording space in the evenings and on weekends, when the building is not in use. The walls are already insulated and I added a second layer of drywall and a solidcore door between the 2 rooms, with plans to add a second layer of drywall to the ceilings when time/money permits. Up until last week, the building did not have heating or cooling. So, he hired a local company to come in and install a HVAC unit and ducting and such. Without consulting me, he decided to have them build a closet and put the HVAC unit in one of the rooms I'm going to be using. I went up there to see how loud it was going to be and it turns out there is so much noise coming from the return air vents that the rooms are unusable while the unit is running, and since there is a return air vent in both rooms there is now an opening for sound to pass from one room to the other. The HVAC unit is inside a closet on a platform about 30 inches off the ground. There are vents on the walls below the platform for the return air. I took the vent covers off to see if that was part of the noise, but it didn't make a noticable difference. It seems like a good deal of the noise is being created by the fan itself, and not just the air rushing through the vents.
What I'm needing to know is, can I build silencers for these return air vents to quiet the HVAC enough to be able to record and mix in these rooms? If so, how big should I make them? What thickness of duct liner should I use in the silencers? Is there something cheaper that I can use, instead of duct liner? Is there anything else I can do to make this work?
I've already spent a lot of time and money on these rooms, so I'm hoping I can still make them work.
Thanks for your help,
Joe
Silencing HVAC Returns
Originally posted at johnlsayers.com, topic 15511.
in general, 2x the area of the duct for the silencer path e.g. if you have an 4"x12" duct then you want 8"x12" (or equiv) for your silencer. this will slow the air flow down by about 50% which will help with air flow noise. use at least 3 turns in the silencer. you also want to check for vibrations (fan unit and ducts), you'll want to seal things up again, and use duct liner in the box to absorb and buffer. you might also want to check with the HVAC company that installed it if they have any recommendations on making the machinery/ducting quieter.
Thats shit!
Do you have some pictures of the unit (brand, size of ducting...ect), cupboard and floor plan.
It will help the guys work out a solution.
lil
I've attach a copy of the floorplan. The measurements aren't exact, but you get the idea. I didn't include the ductwork, since almost all of the noise is coming from the return vents under the HVAC unit. The return vents do not have any ducting, it is just the box that the HVAC is sitting on with vents on the sides. Just guessing, I would say the vents are about 16"x24". Does that mean my silencer boxes would need to be 32"x24"? Is that the size of the vent openning on the other side? Does the path inside of the silencer need to be this dimension also? I don't have a picture of the unit, I can run up there tonight or tomorrow and take one, if it's really necessary. I believe the unit is made by RUUD, but I don't know the model.
since that closet is sitting in the live room you should check for vibrations and and such since your mics could pick that up and in which case you'd want to put that unit on isolator mounts. it might not be an option to reduce the fan speed on the unit and since the returns are right in your room, you're basically listening to the fans almost directly. given size constraints, you might just make the baffle boxes the same size as the returns and live with any air flow noise. where are the returns positioned on that closet? near the top? you might create the baffles as soffits on the ceiling around it to avoid major intrusions into the space where people are walking around.
The returns are at the bottom of the closet. I've attached a rather crude drawing, if that helps.since that closet is sitting in the live room you should check for vibrations and and such since your mics could pick that up and in which case you'd want to put that unit on isolator mounts. it might not be an option to reduce the fan speed on the unit and since the returns are right in your room, you're basically listening to the fans almost directly. given size constraints, you might just make the baffle boxes the same size as the returns and live with any air flow noise. where are the returns positioned on that closet? near the top? you might create the baffles as soffits on the ceiling around it to avoid major intrusions into the space where people are walking around.
ok, so you might as well build out your baffle boxes to essentially enclose the closet walls and have the return openings at the top. in the live room you might have to do something clever like use pin-hinges or latch hooks to connect the unit to the wall so it can be removed to enable access to the closet for servicing.
"What I'm needing to know is, can I build silencers for these return air vents to quiet the HVAC enough to be able to record and mix in these rooms?"
Any restriction you place on return air modifies the way the system is designed to work and that most often means reduced performance and reduced life expectancy on the machine.
As another downer, you essentially have a three way bridge from the control room, live room, and the rest of the building. There are only a few ways out of this and either one is going to require walls to be built to isolate the path.
With hvac guy in tow, then you develop where in the wall your returns will go (room returns as opposed to a system return) that will give you the servive you require and keep the system balanced as needed.
You and your brother-in-law should have a talk first...
In the live room, I can move the vent to the side of the closet that doesn't have the door, so the baffles won't interfere with the functioning of the door. That's a fairly simple drywall job. On the baffle boxes, are you saying that I should build them from floor to ceiling?ok, so you might as well build out your baffle boxes to essentially enclose the closet walls and have the return openings at the top. in the live room you might have to do something clever like use pin-hinges or latch hooks to connect the unit to the wall so it can be removed to enable access to the closet for servicing.
i would do that. then they can be sufficiently sized to properly operate and stay mostly out of the way.
Could you elaborate on this a bit?As another downer, you essentially have a three way bridge from the control room, live room, and the rest of the building. There are only a few ways out of this and either one is going to require walls to be built to isolate the path.
hall way, live room, control room system hvac return is an unobstructed path that cannot be modified.
You said "There are vents on the walls below the platform for the return air." These three sides have filters in them yes?
Sorry, I understood that part. I was hoping you could give some more details about what I can do to fix it. I'm trying to figure out if this is going to be worth the cost and effort to alleviate the problem, or if I should just cut my losses on this space and start looking for something else.hall way, live room, control room system hvac return is an unobstructed path that cannot be modified. You said "There are vents on the walls below the platform for the return air." These three sides have filters in them yes?
here's what i was thinking - two new baffle boxes - floor to ceiling - one in each room. double up the access doors on the hvac unit or make it accessible only from the hallway. this should isolated that closet/returns from each other and the hall. need something soft for the pass-through into the other isolated room baffle box. this drawing just shows the positions of things, the internal baffle box details aren't shown
This looks good to me. Any suggestions on how and what to build the baffles out of?here's what i was thinking - two new baffle boxes - floor to ceiling - one in each room. double up the access doors on the hvac unit or make it accessible only from the hallway. this should isolated that closet/returns from each other and the hall. need something soft for the pass-through into the other isolated room baffle box. this drawing just shows the positions of things, the internal baffle box details aren't shown
i would use 3/4" plywood and line it with Mansville duct liner or use 1" rigid insulation and cover with a thin plastic.
Given that the current return air vents are 16" x 24", should the dimensions of A, B, & C be 16"? Would I keep the same size vent (16x24) for the new return vent, at the top of the baffle? Also, I just remembered that the ductwork for the HVAC comes out of the closet walls where these baffle boxes would be. They are about 9 feet up from the floor. So, would these baffles still be effective if they are only 8 feet tall?
another option would be to build this low and along the wall. yes, you'd want (at a minimum) to have all the open pathways through the boxes to be as large as the returns currently are. or yet another option to extend the supply registers to be further out into the room (which could help with better air flow).
Do the pathways inside the baffle have to be the same dimensions as the current returns, or can I change the dimensions as long as the area is the same. For example, the current returns are 16"x24", which has an area of 384 sq in. Could I make the pathways inside the baffle 10"x42", which is an area of 420 sq in? Sorry for all the questions. I just want to make sure I have it all straight before I attempt any of it.another option would be to build this low and along the wall. yes, you'd want (at a minimum) to have all the open pathways through the boxes to be as large as the returns currently are. or yet another option to extend the supply registers to be further out into the room (which could help with better air flow).
Yes you can alter the dimensions.
Anybody know a cheap place to get duct liner or duct board?